1.
Space telescope
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A space telescope or space observatory is an instrument located in outer space to observe distant planets, galaxies and other astronomical objects. Space telescopes avoid many of the problems of ground-based observatories, such as pollution and distortion of electromagnetic radiation. In addition, ultraviolet frequencies, X-rays and gamma rays are blocked by the Earths atmosphere, Space telescopes are distinct from other imaging satellites pointed toward Earth for purposes of espionage, weather analysis and other types of information gathering. Spitzers proposal called for a telescope that would not be hindered by Earths atmosphere. Performing astronomy from ground-based observatories on Earth is limited by the filtering, some terrestrial telescopes can reduce atmospheric effects with adaptive optics. A telescope orbiting Earth outside the atmosphere is subject neither to twinkling nor to light pollution from artificial light sources on Earth, as a result, the angular resolution of space telescopes is often much smaller than a ground-based telescope with a similar aperture. Infrared and ultraviolet are also largely blocked, however, all these advantages do come with a price. Space telescopes are much more expensive to build than ground-based telescopes, due to their location, space telescopes are also extremely difficult to maintain. The Hubble Space Telescope was serviced by the Space Shuttle while many other space telescopes cannot be serviced at all, Space observatories can generally be divided into two classes, missions which map the entire sky, and observatories which focus on selected astronomical objects or parts of the sky. Many space observatories have already completed their missions, while others continue operating, satellites have been launched and operated by NASA, ISRO, ESA, Japanese Space Agency and the Soviet space program later succeeded by Roskosmos of Russia. Many space telescopes have been launched, as of February 2017, over 20 telescopes are known to be operational
2.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
3.
Ball Aerospace & Technologies
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Ball Aerospace & Technologies Corp. is an American manufacturer of spacecraft, components, and instruments for national defense, civil space and commercial space applications. Ball Aerospace began building pointing controls for military rockets in 1956, and later won a contract to one of NASA’s first spacecraft. Over the years, the company has been responsible for technological and scientific projects and continues to provide aerospace technology to NASA. Ball Aerospace also has other products and services for the aerospace industry, including lubricants, optical systems, star trackers. As a wholly owned subsidiary of the Ball Corporation, Ball Aerospace was cited in 2014 as the 88th largest defense contractor in the world, both parent and subsidiary headquarters are co-located in Broomfield, Colorado. The Wide-field Infrared Survey Explorer Program, which, over a mission in a polar orbit will map the entire sky in multiple mid-far infrared wavelengths. This crucial mission may find close and cool objects to our sun never before detected and it will also act as a predecessor to the JWST Program. The Opticks remote sensing data visualization application, the Sentinel space observatory, a satellite in Venusian orbit which will scout for hazardous asteroids. The Arizona State University, thermal imaging system for Nasas mission to study the Jupiter moon. DigitalGlobes remote sensing spacecraft, QuickBird, WorldView-1, and WorldView-2 The instrumentation for the Spitzer Space Telescope, Ball Aerospace developed the Cryogenic Telescope Assembly and two of the three science instruments, the Infrared Spectrograph and the Multiband Imaging Photometer. After the servicing mission was completed, all of Hubbles scientific instruments are of Ball Aerospace manufacture, AEROS CALIPSO, a joint NASA and CNES environmental spacecraft CloudSat, a NASA Earth observation spacecraft Deep Impact spacecraft. Ball Aerospace designed and built the spacecraft and all of its instrument packages for NASA
4.
Fokker
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Fokker was a Dutch aircraft manufacturer named after its founder, Anthony Fokker. The company operated several different names, starting out in 1912 in Schwerin, Germany. During its most successful period in the 1920s and 1930s, it dominated the civil aviation market, Fokker went into bankruptcy in 1996, and its operations were sold to competitors. At age 20, while studying in Germany, Anthony Fokker built his initial aircraft, Fokker capitalized on having sold several Fokker Spin monoplanes to the German government and set up a factory in Germany to supply the German Army. His first new design for the Germans to be produced in any numbers was the Fokker M, when it was realized that arming these scouts with a machine gun firing through the propeller was desirable, Fokker developed a synchronization gear similar to that patented by Franz Schneider. Fitted with a version of this gear, the M.2. Later in the war, after the Fokker D, as this partnership proved to be troublesome, it was eventually dissolved again. In 1919, Fokker, owing large sums in back taxes, returned to the Netherlands and founded a new company near Amsterdam with the support of Steenkolen Handels Vereniging and he chose the name Nederlandse Vliegtuigenfabriek to conceal the Fokker brand because of his World War I involvement. Despite the strict disarmament conditions in the Treaty of Versailles, Fokker did not return home empty-handed. In 1919, he arranged an export permit and brought six entire trains of parts, and 180 types of aircraft across the Dutch-German border, among them 117 Fokker C. Is, D. VIIs and this initial stock enabled him to set up shop quickly. After his companys relocation, many Fokker C. I and C. IV military airplanes were delivered to Russia, Romania, and the still clandestine German air force. Success came on the market, too, with the development of the Fokker F. VII. Fokker continued to design and build aircraft, delivering planes to the Royal Netherlands Air Force. Foreign military customers eventually included Finland, Sweden, Denmark, Norway, Switzerland, Hungary and these countries bought substantial numbers of the Fokker C. V reconnaissance aircraft, which became Fokkers main success in the late 1920s and early 1930s. In the 1920s, Fokker entered its glory years, becoming the worlds largest aircraft manufacturer by the late 1920s and its greatest success was the 1925 F. VIIa/3m trimotor passenger aircraft, which was used by 54 airline companies worldwide and captured 40% of the American market in 1936. A serious blow to Fokkers reputation came after the 1931 TWA Flight 599 disaster in Kansas, notre Dame legendary football coach Knute Rockne was among the fatalities, prompting extensive media coverage and technical investigation. As a result, all Fokkers were grounded in the USA, in 1931, discontented at being totally subordinate to GM management, Fokker resigned. On December 23,1939, he died in New York City, the Fokker factories were confiscated by the Germans and were used to build Bücker Bü181 Bestmann trainers and parts for the Junkers Ju 52 transport
5.
Thales Nederland
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Thales Nederland B. V. is a subsidiary of Thales Group involved primarily in naval defence systems. Other areas of business include air defence, communications, optronics, cryogenic cooling systems, the company was founded in 1922 in Hengelo as NV Hazemeyers Fabriek van Signaalapparaten by Hazemeyer and Siemens & Halske for the development of naval fire-control systems. It was way to get around the restrictions of the Treaty of Versailles which did not allow German companies to manufacture military equipment, in 1940 the companys factory was captured by the invading German Army. After the war the company was nationalised as N. V. Hollandse Signaalapparaten, in 1956 the majority of Signaal shares were purchased by Philips, a Netherlands-based electronics company. Between 1956 and the end of the Cold War Signaals business expanded to the point where it had customers in 35 countries, in 1990 Philips decided defence was not a core activity and sold Signaal to Thomson-CSF, a French electronics and defence contractor. With the renaming of Thomson to Thales in 2000 Thomson-CSF Signaal became Thales Nederland. V
6.
Delta 3000
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The Delta 3000 series was an American expendable launch system which was used to conduct 38 orbital launches between 1975 and 1989. It was a member of the Delta family of rockets, several variants existed, which were differentiated by a four digit numerical code. The first stage was the RS-27 powered Extended Long Tank Thor, three or nine Castor-4 solid rocket boosters were attached to increase thrust at lift-off, replacing the less powerful Castor-2 boosters used on earlier models. Two second stages were available, the Delta-P, which had flown on the Delta 1000 and 2000 series, or the Delta-K. Some launches used a configuration in order to reach higher orbits. A Star-37D, Star-37E, or Star-48B PAM-D could be used as an upper stage, launches with PAM-D upper stages were designated Delta 3XX0 PAM-D, rather than assigning a code to the upper stage for use in the four-digit sequence. From the 4000-series onwards, the PAM-D received the upper stage code 5, however this was not applied retrospectively to 3000-series rockets, the Delta 3000 could put a payload of 954 kg to a GTO. The Delta 3000 was launched from Space Launch Complex 2W at Vandenberg AFB and Launch Complex 17A, of the 35 launches, there were two complete and one partial failure. The first, Vehicle 134 lifted from LC-17A at Cape Canaveral on September 13,1977 with an Italian-built OTS communications satellite, fifty-two seconds after liftoff, the Delta exploded. When the booster had been assembled on the pad the previous May, the payload fairing disintegrated at vehicle breakup and the OTS satellite was ripped apart by aerodynamic loads. Parts of the panels, batteries, and hydrazine propellant tanks were recovered from the ocean. There had been an upper stage failure of a Delta 2000 series in April, NASA was particularly vexed by the string of accidents in 1977 because they had had a perfect run the year before. The second Delta 3000 failure, Vehicle 150, was launched on December 7,1979, the third, Vehicle 178, launched on May 3,1986 with a GOES weather satellite. This was televised on CNN to mark NASAs first launch since the Challenger Disaster four months earlier, the Delta performed normally until T+71 seconds when the main engine abruptly shut off. With no attitude control, the vehicle began tumbling violently. The shroud, payload, and third stage were ripped away followed several seconds later by Range Safety issuing the destruct command, the GOES-G satellite was lost in the incident. It was the first time an electrical failure had occurred in a Delta since its introduction in 1960, as the solid rocket motors had fixed nozzles with no gimbaling ability, the booster became completely uncontrollable without the main engine. Delta 178 was the first failed launch since 134 nine years earlier and marked the end of 42 consecutive flights without a failure, investigators ultimately traced the incident to a damaged wiring harness, there had recently been a switch from polyvinyl chloride wire insulation to Teflon
7.
Vandenberg Air Force Base
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Vandenberg Air Force Base is a United States Air Force Base 9.2 miles northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command, Vandenberg AFB is a Department of Defense space and missile testing base, with a mission of placing satellites into polar orbit from the West Coast using expendable boosters. Wing personnel also support the Services LGM-30G Minuteman III Intercontinental Ballistic Missile Force Development Evaluation program, in addition to its military mission, the base also leases launch pad facilities to SpaceX, as well as 100 acres leased to the California Spaceport in 1995. Established in 1941, the base is named in honor of former Air Force Chief of Staff General Hoyt Vandenberg, the host unit at Vandenberg AFB is the 30th Space Wing. The 30th SW is home to the Western Range, manages Department of Defense space and missile testing, Wing personnel also support the Air Forces Minuteman III Intercontinental Ballistic Missile Force Development Test and Evaluation program. The Western Range begins at the boundaries of Vandenberg and extends westward from the California coast to the Western Pacific. Operations involve dozens of federal and commercial interests, the wing is organized into operations, launch, mission support and medical groups, along with several directly assigned staff agencies. 30th Launch Group The 30th Launch Group is responsible for booster and satellite technical oversight and launch processing activities to launch, integration. The group consists of a military, civilian and contractor team with more than 250 personnel directly supporting operations from the Western Range. 1st Air and Space Test Squadron 4th Space Launch Squadron 30th Operations Group The 30th Operations Group provides the capability for West Coast spacelift. Operations professionals are responsible for operating and maintaining the Western Range for spacelift, missile test launch, aeronautical, 30th Mission Support Group The 30th Mission Support Group supports the third largest Air Force Base in the United States. It is also responsible for quality-of-life needs, housing, personnel, services, civil engineering, contracting, 30th Medical Group The 30th Medical Group provides medical, dental, bio-environmental and public health services for people assigned to Vandenberg Air Force Base, their families and retirees. It is Vandenbergs only National Historic Landmark that is open for scheduled tours through the 30th Space Wings Public Affairs office. The current display area is made up of two exhibits, the Chronology of the Cold War and the Evolution of Technology, there are plans to evolve the center in stages from the current exhibit areas as restorations of additional facilities are completed. In 1941 the United States Army sought more and better training centers for the development of its armored. In March 1941, the Army acquired approximately 86,000 acres of open ranch lands along the Central Coast of California between Lompoc and Santa Maria, most of the land was purchased. Smaller parcels were obtained either by lease, license, or as easements, with its flat plateau, surrounding hills, numerous canyons, and relative remoteness from populated areas, the Army was convinced it had found the ideal training location. Construction of the Army camp began in September 1941, although its completion was still months away, the Army activated the camp on 5 October, and named it Camp Cooke in honor of Major General Phillip St. George Cooke
8.
Vandenberg AFB Space Launch Complex 2
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Space Launch Complex 2 is an active rocket launch site at Vandenberg Air Force Base, in California, USA. It consists of two launch pads, the East pad, which has been demolished, was used for Delta, Thor-Agena and Thorad launches between 1966 and 1972. The West pad, SLC-2W, has used for Delta, Thor-Agena, and Delta II launches since 1966. Space Launch Complex 2 was originally part of Launch Complex 75, when this complex was split up in 1966, the first launch to be made from the newly redesignated Space Launch Complex 2 was that of a Delta E with ESSA-3 on 2 October 1966 from SLC-2E. The first launch from SLC-2W after redesignation was of a Thor-Agena with OPS1584 on 29 December 1966, SLC-2E and SLC-2W are located approximately 2,000 feet apart
9.
Geocentric orbit
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A geocentric orbit or Earth orbit involves any object orbiting the Earth, such as the Moon or artificial satellites. In 1997 NASA estimated there were approximately 2,465 artificial satellite orbiting the Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. Over 16,291 previously launched objects have decayed into the Earths atmosphere, altitude as used here, the height of an object above the average surface of the Earths oceans. Analemma a term in astronomy used to describe the plot of the positions of the Sun on the celestial sphere throughout one year, apogee is the farthest point that a satellite or celestial body can go from Earth, at which the orbital velocity will be at its minimum. Eccentricity a measure of how much an orbit deviates from a perfect circle, eccentricity is strictly defined for all circular and elliptical orbits, and parabolic and hyperbolic trajectories. Equatorial plane as used here, an imaginary plane extending from the equator on the Earth to the celestial sphere, escape velocity as used here, the minimum velocity an object without propulsion needs to have to move away indefinitely from the Earth. An object at this velocity will enter a parabolic trajectory, above this velocity it will enter a hyperbolic trajectory, impulse the integral of a force over the time during which it acts. Inclination the angle between a plane and another plane or axis. In the sense discussed here the reference plane is the Earths equatorial plane, orbital characteristics the six parameters of the Keplerian elements needed to specify that orbit uniquely. Orbital period as defined here, time it takes a satellite to make one orbit around the Earth. Perigee is the nearest approach point of a satellite or celestial body from Earth, sidereal day the time it takes for a celestial object to rotate 360°. For the Earth this is,23 hours,56 minutes,4.091 seconds, solar time as used here, the local time as measured by a sundial. Velocity an objects speed in a particular direction, since velocity is defined as a vector, both speed and direction are required to define it. The following is a list of different geocentric orbit classifications, Low Earth orbit - Geocentric orbits ranging in altitude from 160 kilometers to 2,000 kilometres above mean sea level. At 160 km, one revolution takes approximately 90 minutes, medium Earth orbit - Geocentric orbits with altitudes at apogee ranging between 2,000 kilometres and that of the geosynchronous orbit at 35,786 kilometres. Geosynchronous orbit - Geocentric circular orbit with an altitude of 35,786 kilometres, the period of the orbit equals one sidereal day, coinciding with the rotation period of the Earth. The speed is approximately 3,000 metres per second, high Earth orbit - Geocentric orbits with altitudes at apogee higher than that of the geosynchronous orbit. A special case of high Earth orbit is the elliptical orbit
10.
Sun-synchronous orbit
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A Sun-synchronous orbit is a geocentric orbit that combines altitude and inclination in such a way that the satellite passes over any given point of the planets surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, more technically, it is an orbit arranged in such a way that it precesses once a year. The surface illumination angle will be nearly the same time that the satellite is overhead. This consistent lighting is a characteristic for satellites that image the Earths surface in visible or infrared wavelengths. For example, a satellite in sun-synchronous orbit might ascend across the twelve times a day each time at approximately 15,00 mean local time. This is achieved by having the orbital plane precess approximately one degree each day with respect to the celestial sphere, eastward. Typical sun-synchronous orbits are about 600–800 km in altitude, with periods in the 96–100 minute range, riding the terminator is useful for active radar satellites as the satellites solar panels can always see the Sun, without being shadowed by the Earth. The dawn/dusk orbit has been used for solar observing scientific satellites such as Yohkoh, TRACE, Hinode and PROBA2, Sun-synchronous orbits can happen around other oblate planets, such as Mars. A satellite around the almost spherical Venus, for example, will need an outside push to be in a sun-synchronous orbit.696 deg. Note that according to this approximation cos i equals −1 when the semi-major axis equals 12352 km, the period can be in the range from 88 minutes for a very low orbit to 3.8 hours. If one wants a satellite to fly over some given spot on Earth every day at the same hour, it can do between 7 and 16 orbits per day, as shown in the following table. When one says that a Sun-synchronous orbit goes over a spot on the earth at the local time each time. The Sun will not be in exactly the same position in the sky during the course of the year, very often a frozen orbit is therefore selected that is slightly higher over the Southern hemisphere than over the Northern hemisphere. ERS-1, ERS-2 and Envisat of European Space Agency as well as the MetOp spacecraft of EUMETSAT are all operated in Sun-synchronous, orbital perturbation analysis Analemma Geosynchronous orbit Geostationary orbit List of orbits Polar orbit World Geodetic System Sandwell, David T. The Gravity Field of the Earth - Part 1 Sun-Synchronous Orbit dictionary entry, centennial of Flight Commission NASA Q&A Boain, Ronald J. The A-B-Cs of Sun Synchronous Orbit Design, List of satellites in Sun-synchronous orbit
11.
Semi-major and semi-minor axes
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In geometry, the major axis of an ellipse is its longest diameter, a line segment that runs through the center and both foci, with ends at the widest points of the perimeter. The semi-major axis is one half of the axis, and thus runs from the centre, through a focus. Essentially, it is the radius of an orbit at the two most distant points. For the special case of a circle, the axis is the radius. One can think of the axis as an ellipses long radius. The semi-major axis of a hyperbola is, depending on the convention, thus it is the distance from the center to either vertex of the hyperbola. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction. Thus a and b tend to infinity, a faster than b, the semi-minor axis is a line segment associated with most conic sections that is at right angles with the semi-major axis and has one end at the center of the conic section. It is one of the axes of symmetry for the curve, in an ellipse, the one, in a hyperbola. The semi-major axis is the value of the maximum and minimum distances r max and r min of the ellipse from a focus — that is. In astronomy these extreme points are called apsis, the semi-minor axis of an ellipse is the geometric mean of these distances, b = r max r min. The eccentricity of an ellipse is defined as e =1 − b 2 a 2 so r min = a, r max = a. Now consider the equation in polar coordinates, with one focus at the origin, the mean value of r = ℓ / and r = ℓ /, for θ = π and θ =0 is a = ℓ1 − e 2. In an ellipse, the axis is the geometric mean of the distance from the center to either focus. The semi-minor axis of an ellipse runs from the center of the ellipse to the edge of the ellipse, the semi-minor axis is half of the minor axis. The minor axis is the longest line segment perpendicular to the axis that connects two points on the ellipses edge. The semi-minor axis b is related to the axis a through the eccentricity e. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction
12.
Orbital eccentricity
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The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is an orbit, values between 0 and 1 form an elliptical orbit,1 is a parabolic escape orbit. The term derives its name from the parameters of conic sections and it is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit, the eccentricity of this Kepler orbit is a non-negative number that defines its shape. The limit case between an ellipse and a hyperbola, when e equals 1, is parabola, radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one, keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1. For a repulsive force only the trajectory, including the radial version, is applicable. For elliptical orbits, a simple proof shows that arcsin yields the projection angle of a circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury, next, tilt any circular object by that angle and the apparent ellipse projected to your eye will be of that same eccentricity. From Medieval Latin eccentricus, derived from Greek ἔκκεντρος ekkentros out of the center, from ἐκ- ek-, eccentric first appeared in English in 1551, with the definition a circle in which the earth, sun. Five years later, in 1556, a form of the word was added. The eccentricity of an orbit can be calculated from the state vectors as the magnitude of the eccentricity vector, e = | e | where. For elliptical orbits it can also be calculated from the periapsis and apoapsis since rp = a and ra = a, where a is the semimajor axis. E = r a − r p r a + r p =1 −2 r a r p +1 where, rp is the radius at periapsis. For Earths annual orbit path, ra/rp ratio = longest_radius / shortest_radius ≈1.034 relative to center point of path, the eccentricity of the Earths orbit is currently about 0.0167, the Earths orbit is nearly circular. Venus and Neptune have even lower eccentricity, over hundreds of thousands of years, the eccentricity of the Earths orbit varies from nearly 0.0034 to almost 0.058 as a result of gravitational attractions among the planets. The table lists the values for all planets and dwarf planets, Mercury has the greatest orbital eccentricity of any planet in the Solar System. Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion, before its demotion from planet status in 2006, Pluto was considered to be the planet with the most eccentric orbit
13.
Apsis
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An apsis is an extreme point in an objects orbit. The word comes via Latin from Greek and is cognate with apse, for elliptic orbits about a larger body, there are two apsides, named with the prefixes peri- and ap-, or apo- added to a reference to the thing being orbited. For a body orbiting the Sun, the point of least distance is the perihelion, the terms become periastron and apastron when discussing orbits around other stars. For any satellite of Earth including the Moon the point of least distance is the perigee, for objects in Lunar orbit, the point of least distance is the pericynthion and the greatest distance the apocynthion. For any orbits around a center of mass, there are the terms pericenter and apocenter, periapsis and apoapsis are equivalent alternatives. A straight line connecting the pericenter and apocenter is the line of apsides and this is the major axis of the ellipse, its greatest diameter. For a two-body system the center of mass of the lies on this line at one of the two foci of the ellipse. When one body is larger than the other it may be taken to be at this focus. Historically, in systems, apsides were measured from the center of the Earth. In orbital mechanics, the apsis technically refers to the distance measured between the centers of mass of the central and orbiting body. However, in the case of spacecraft, the family of terms are used to refer to the orbital altitude of the spacecraft from the surface of the central body. The arithmetic mean of the two limiting distances is the length of the axis a. The geometric mean of the two distances is the length of the semi-minor axis b, the geometric mean of the two limiting speeds is −2 ε = μ a which is the speed of a body in a circular orbit whose radius is a. The words pericenter and apocenter are often seen, although periapsis/apoapsis are preferred in technical usage, various related terms are used for other celestial objects. The -gee, -helion and -astron and -galacticon forms are used in the astronomical literature when referring to the Earth, Sun, stars. The suffix -jove is occasionally used for Jupiter, while -saturnium has very rarely used in the last 50 years for Saturn. The -gee form is used as a generic closest approach to planet term instead of specifically applying to the Earth. During the Apollo program, the terms pericynthion and apocynthion were used when referring to the Moon, regarding black holes, the term peri/apomelasma was used by physicist Geoffrey A. Landis in 1998 before peri/aponigricon appeared in the scientific literature in 2002
14.
Orbital inclination
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Orbital inclination measures the tilt of an objects orbit around a celestial body. It is expressed as the angle between a plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the equator, the plane of the orbit is the same as the Earths equatorial plane. The general case is that the orbit is tilted, it spends half an orbit over the northern hemisphere. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°, the inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planets equator, for planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. This reference plane is most practical for Earth-based observers, therefore, Earths inclination is, by definition, zero. Inclination could instead be measured with respect to another plane, such as the Suns equator or the invariable plane, the inclination of orbits of natural or artificial satellites is measured relative to the equatorial plane of the body they orbit, if they orbit sufficiently closely. The equatorial plane is the perpendicular to the axis of rotation of the central body. An inclination of 30° could also be described using an angle of 150°, the convention is that the normal orbit is prograde, an orbit in the same direction as the planet rotates. Inclinations greater than 90° describe retrograde orbits, thus, An inclination of 0° means the orbiting body has a prograde orbit in the planets equatorial plane. An inclination greater than 0° and less than 90° also describe prograde orbits, an inclination of 63. 4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. An inclination of exactly 90° is an orbit, in which the spacecraft passes over the north and south poles of the planet. An inclination greater than 90° and less than 180° is a retrograde orbit, an inclination of exactly 180° is a retrograde equatorial orbit. For gas giants, the orbits of moons tend to be aligned with the giant planets equator, the inclination of exoplanets or members of multiple stars is the angle of the plane of the orbit relative to the plane perpendicular to the line-of-sight from Earth to the object. An inclination of 0° is an orbit, meaning the plane of its orbit is parallel to the sky. An inclination of 90° is an orbit, meaning the plane of its orbit is perpendicular to the sky
15.
Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
16.
Astronomical survey
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An astronomical survey is a general map or image of a region of the sky which lacks a specific observational target. Alternatively, a survey may comprise a set of many images or spectra of objects which share a common type or feature. Surveys have generally performed as part of the production of an astronomical catalog. In some cases, an interested in a particular object will find that survey images are sufficient to make telescope time entirely unnecessary. Surveys also help astronomers obtain observation time on larger, more powerful telescopes, if the astronomer can show a telescope scheduling committee that previous observations support his or her hypothesis, he or she is more likely to be given a chance to make more detailed observations. The wide scope of surveys makes them ideal for astronomers searching for moving objects such as asteroids. An astronomer can compare existing survey images to current observations to locate targets which are in motion, similarly, images of the same object taken by different surveys can be compared to detect transient events such as variable stars. It began in 1977 to 1982 then from 1985 to 1995.3,4.7,12, the telescope is over a thousand times as sensitive as previous infrared surveys. The initial survey, consisting of each sky position imaged at least eight times, was completed by July 2010, 1997–2002 Ohio Sky Survey – Over 19,000 radio sources at 1415 MHz. NVSS – Survey at 1.4 GHz mapping the sky north of −40 deg FIRST – Survey to look for faint radio sources at twenty cms, PALFA Survey – On-going 1.4 GHz survey for radio pulsars using the Arecibo Observatory. 2008–present, the goal for the lifetime is 10 years. The resulting dataset aims to be a resource for studying the physics of the galaxy population. GOODS – The Great Observatories Origins Deep Survey, COSMOS – The Cosmic Evolution Survey. Atlas 3d Survey – sample of 260 galaxies for the Astrophysics project, timeline of astronomical maps, catalogs, and surveys
17.
Night sky
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The term night sky refers to the sky as seen at night. The term is associated with astronomy, with reference to views of celestial bodies such as stars, the Moon. Natural light sources in a night sky include moonlight, starlight, the aurora borealis and aurora australis light up the skies of the Arctic and Antarctic circles respectively. Occasionally, a large coronal mass ejection from the Sun or simply high levels of solar wind extend the phenomenon toward the equator, the night sky and studies of it have a historical place in both ancient and modern cultures. In the past, for instance, farmers have used the state of the sky as a calendar to determine when to plant crops. Many cultures have drawn constellations between stars in the sky, using them in association with legends and mythology about their deities, the anciently developed belief of astrology is generally based on the belief that relationships between heavenly bodies influence or convey information about events on Earth. The scientific study of the sky and bodies observed within it, meanwhile. The visibility of objects in the night sky is affected by light pollution. The presence of the Moon in the sky has historically hindered astronomical observation by increasing the amount of ambient lighting. With the advent of light sources, however, light pollution has been a growing problem for viewing the night sky. The intensity of the sky varies greatly over the day and the cause differs as well. During daytime when the sun is above the horizon direct scattering of sunlight is the dominant source of light. In twilight, the period of time between sunset and sunrise, the situation is complicated and a further differentiation is required. Twilight is divided in three segments according to how far the sun is below the horizon in segments of 6°, after sunset the civil twilight sets in, and ends when the sun drops more than 6° below the horizon. This is followed by the nautical twilight, when the sun reaches heights of -6° and -12°, when the sun drops more than 18° below the horizon the sky generally attains its minimum brightness. Several sources can be identified as the source of the brightness of the sky, namely airglow, indirect scattering of sunlight, scattering of starlight. Stars appear as, depending on how dark the sky is, to the naked eye, they all appear to be equidistant on a dome above the earth because stars are much too far away for stereopsis to offer any depth cues. Visible stars range in color from blue to red, but with small points of faint light
18.
Wavelength
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In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the waves shape repeats, and thus the inverse of the spatial frequency. Wavelength is commonly designated by the Greek letter lambda, the concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also applied to modulated waves. Wavelength depends on the medium that a wave travels through, examples of wave-like phenomena are sound waves, light, water waves and periodic electrical signals in a conductor. A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric, water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary, wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle near the waters surface moves in a circle of the same diameter as the wave height. The range of wavelengths or frequencies for wave phenomena is called a spectrum, the name originated with the visible light spectrum but now can be applied to the entire electromagnetic spectrum as well as to a sound spectrum or vibration spectrum. In linear media, any pattern can be described in terms of the independent propagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by λ = v f, in a dispersive medium, the phase speed itself depends upon the frequency of the wave, making the relationship between wavelength and frequency nonlinear. In the case of electromagnetic radiation—such as light—in free space, the speed is the speed of light. Thus the wavelength of a 100 MHz electromagnetic wave is about, the wavelength of visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm. For sound waves in air, the speed of sound is 343 m/s, the wavelengths of sound frequencies audible to the human ear are thus between approximately 17 m and 17 mm, respectively. Note that the wavelengths in audible sound are much longer than those in visible light, a standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, the upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box determining which wavelengths are allowed, the stationary wave can be viewed as the sum of two traveling sinusoidal waves of oppositely directed velocities. Consequently, wavelength, period, and wave velocity are related just as for a traveling wave, for example, the speed of light can be determined from observation of standing waves in a metal box containing an ideal vacuum. In that case, the k, the magnitude of k, is still in the same relationship with wavelength as shown above
19.
United States
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Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
20.
Netherlands
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The Netherlands, also informally known as Holland is the main constituent country of the Kingdom of the Netherlands. It is a densely populated country located in Western Europe with three territories in the Caribbean. The European part of the Netherlands borders Germany to the east, Belgium to the south, and the North Sea to the northwest, sharing borders with Belgium, the United Kingdom. The three largest cities in the Netherlands are Amsterdam, Rotterdam and The Hague, Amsterdam is the countrys capital, while The Hague holds the Dutch seat of parliament and government. The port of Rotterdam is the worlds largest port outside East-Asia, the name Holland is used informally to refer to the whole of the country of the Netherlands. Netherlands literally means lower countries, influenced by its low land and flat geography, most of the areas below sea level are artificial. Since the late 16th century, large areas have been reclaimed from the sea and lakes, with a population density of 412 people per km2 –507 if water is excluded – the Netherlands is classified as a very densely populated country. Only Bangladesh, South Korea, and Taiwan have both a population and higher population density. Nevertheless, the Netherlands is the worlds second-largest exporter of food and agricultural products and this is partly due to the fertility of the soil and the mild climate. In 2001, it became the worlds first country to legalise same-sex marriage, the Netherlands is a founding member of the EU, Eurozone, G-10, NATO, OECD and WTO, as well as being a part of the Schengen Area and the trilateral Benelux Union. The first four are situated in The Hague, as is the EUs criminal intelligence agency Europol and this has led to the city being dubbed the worlds legal capital. The country also ranks second highest in the worlds 2016 Press Freedom Index, the Netherlands has a market-based mixed economy, ranking 17th of 177 countries according to the Index of Economic Freedom. It had the thirteenth-highest per capita income in the world in 2013 according to the International Monetary Fund, in 2013, the United Nations World Happiness Report ranked the Netherlands as the seventh-happiest country in the world, reflecting its high quality of life. The Netherlands also ranks joint second highest in the Inequality-adjusted Human Development Index, the region called Low Countries and the country of the Netherlands have the same toponymy. Place names with Neder, Nieder, Nether and Nedre and Bas or Inferior are in use in all over Europe. They are sometimes used in a relation to a higher ground that consecutively is indicated as Upper, Boven, Oben. In the case of the Low Countries / the Netherlands the geographical location of the region has been more or less downstream. The geographical location of the region, however, changed over time tremendously
21.
United Kingdom
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The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or Britain, is a sovereign country in western Europe. Lying off the north-western coast of the European mainland, the United Kingdom includes the island of Great Britain, Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. The Irish Sea lies between Great Britain and Ireland, with an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world and the 11th-largest in Europe. It is also the 21st-most populous country, with an estimated 65.1 million inhabitants, together, this makes it the fourth-most densely populated country in the European Union. The United Kingdom is a monarchy with a parliamentary system of governance. The monarch is Queen Elizabeth II, who has reigned since 6 February 1952, other major urban areas in the United Kingdom include the regions of Birmingham, Leeds, Glasgow, Liverpool and Manchester. The United Kingdom consists of four countries—England, Scotland, Wales, the last three have devolved administrations, each with varying powers, based in their capitals, Edinburgh, Cardiff and Belfast, respectively. The relationships among the countries of the UK have changed over time, Wales was annexed by the Kingdom of England under the Laws in Wales Acts 1535 and 1542. A treaty between England and Scotland resulted in 1707 in a unified Kingdom of Great Britain, which merged in 1801 with the Kingdom of Ireland to form the United Kingdom of Great Britain and Ireland. Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain, there are fourteen British Overseas Territories. These are the remnants of the British Empire which, at its height in the 1920s, British influence can be observed in the language, culture and legal systems of many of its former colonies. The United Kingdom is a country and has the worlds fifth-largest economy by nominal GDP. The UK is considered to have an economy and is categorised as very high in the Human Development Index. It was the worlds first industrialised country and the worlds foremost power during the 19th, the UK remains a great power with considerable economic, cultural, military, scientific and political influence internationally. It is a nuclear weapons state and its military expenditure ranks fourth or fifth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946 and it has been a leading member state of the EU and its predecessor, the European Economic Community, since 1973. However, on 23 June 2016, a referendum on the UKs membership of the EU resulted in a decision to leave. The Acts of Union 1800 united the Kingdom of Great Britain, Scotland, Wales and Northern Ireland have devolved self-government
22.
California Institute of Technology
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The California Institute of Technology is a private doctorate-granting university located in Pasadena, California, United States. The vocational and preparatory schools were disbanded and spun off in 1910, the university is one among a small group of Institutes of Technology in the United States which is primarily devoted to the instruction of technical arts and applied sciences. Caltech has six divisions with strong emphasis on science and engineering, managing $332 million in 2011 in sponsored research. Its 124-acre primary campus is located approximately 11 mi northeast of downtown Los Angeles, first-year students are required to live on campus, and 95% of undergraduates remain in the on-campus House System at Caltech. Although Caltech has a tradition of practical jokes and pranks. The Caltech Beavers compete in 13 intercollegiate sports in the NCAA Division IIIs Southern California Intercollegiate Athletic Conference, Caltech is frequently cited as one of the worlds best universities. There are 112 faculty members who have elected to the United States National Academies. In addition, numerous faculty members are associated with the Howard Hughes Medical Institute as well as NASA, according to a 2015 Pomona College study, Caltech ranked number one in the U. S. for the percentage of its graduates who go on to earn a PhD. Caltech started as a school founded in Pasadena in 1891 by local businessman and politician Amos G. Throop. The school was known successively as Throop University, Throop Polytechnic Institute, the vocational school was disbanded and the preparatory program was split off to form an independent Polytechnic School in 1907. At a time when research in the United States was still in its infancy, George Ellery Hale. He joined Throops board of trustees in 1907, and soon began developing it and he engineered the appointment of James A. B. Scherer, a literary scholar untutored in science but a capable administrator and fund raiser, scherer persuaded retired businessman and trustee Charles W. Gates to donate $25,000 in seed money to build Gates Laboratory, the first science building on campus. In 1910, Throop moved to its current site, arther Fleming donated the land for the permanent campus site. The promise of Throop attracted physical chemist Arthur Amos Noyes from MIT to develop the institution and assist in establishing it as a center for science, with the onset of World War I, Hale organized the National Research Council to coordinate and support scientific work on military problems. This institution, with its able investigators and excellent research laboratories, through the National Research Council, Hale simultaneously lobbied for science to play a larger role in national affairs, and for Throop to play a national role in science. During the course of the war, Hale, Noyes and Millikan worked together in Washington on the NRC, subsequently, they continued their partnership in developing Caltech. Under the leadership of Hale, Noyes and Millikan, Caltech grew to prominence in the 1920s
23.
Spitzer Space Telescope
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The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility, is an infrared space telescope launched in 2003. It is the fourth and final of the NASA Great Observatories program, the planned mission period was to be 2.5 years with a pre-launch expectation that the mission could extend to five or slightly more years until the onboard liquid helium supply was exhausted. This occurred on 15 May 2009, without liquid helium to cool the telescope to the very low temperatures needed to operate, most of the instruments are no longer usable. All Spitzer data, from both the primary and warm phases, are archived at the Infrared Science Archive, in keeping with NASA tradition, the telescope was renamed after its successful demonstration of operation, on 18 December 2003. Unlike most telescopes that are named after famous deceased astronomers by a board of scientists, the contest led to the telescope being named in honor of astronomer Lyman Spitzer, who had promoted the concept of space telescopes in the 1940s. Spitzer wrote a 1946 report for RAND Corporation describing the advantages of an extraterrestrial observatory, the US$720 million Spitzer was launched on 25 August 2003 at 05,35,39 UTC from Cape Canaveral SLC-17B aboard a Delta II 7920H rocket. It follows a heliocentric instead of orbit, trailing and drifting away from Earths orbit at approximately 0.1 astronomical unit per year. The primary mirror is 85 centimeters in diameter, f/12, made of beryllium and was cooled to 5.5 K, by the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of Earths atmosphere. Anticipating the major results from an upcoming Explorer satellite and from the Shuttle mission, long-duration spaceflights of infrared telescopes cooled to cryogenic temperatures. Earlier infrared observations had been made by both space-based and ground-based observatories, ground-based observatories have the drawback that at infrared wavelengths or frequencies, both the Earths atmosphere and the telescope itself will radiate strongly. Additionally, the atmosphere is opaque at most infrared wavelengths and this necessitates lengthy exposure times and greatly decreases the ability to detect faint objects. It could be compared to trying to observe the stars at noon, previous space observatories were launched during the 1980s and 1990s and great advances in astronomical technology have been made since then. Most of the early concepts envisioned repeated flights aboard the NASA Space Shuttle and this approach was developed in an era when the Shuttle program was expected to support weekly flights of up to 30 days duration. A May 1983 NASA proposal described SIRTF as a Shuttle-attached mission, several flights were anticipated with a probable transition into a more extended mode of operation, possibly in association with a future space platform or space station. SIRTF would be a 1-meter class, cryogenically cooled, multi-user facility consisting of a telescope, the first flight was expected to occur about 1990, with the succeeding flights anticipated beginning approximately one year later. By September 1983 NASA was considering the possibility of a long duration SIRTF mission, Spitzer is the only one of the Great Observatories not launched by the Space Shuttle, as was originally intended. However, after the 1986 Challenger disaster, the Centaur LH2–LOX upper stage, the mission underwent a series of redesigns during the 1990s, primarily due to budget considerations. This resulted in a smaller but still fully capable mission that could use the smaller Delta II expendable launch vehicle
24.
Infrared Space Observatory
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The Infrared Space Observatory was a space telescope for infrared light designed and operated by the European Space Agency, in cooperation with ISAS and NASA. The ISO was designed to study infrared light at wavelengths of 2.5 to 240 micrometres, the €480. 1-million satellite was launched on 17 November 1995 from the ELA-2 launch pad at the Guiana Space Centre near Kourou in French Guiana. The launch vehicle, an Ariane 44P rocket, placed ISO successfully into an elliptical geocentric orbit. The primary mirror of its Ritchey-Chrétien telescope measured 60 cm in diameter and was cooled to 1.7 Kelvin by means of superfluid helium. The ISO satellite contained four instruments that allowed for imaging and photometry from 2.5 to 240 micrometres, currently, ESA and IPAC continue efforts to improve the data pipelines and specialized software analysis tools to yield the best quality calibration and data reduction methods from the mission. IPAC supports ISO observers and data archive users through in-house visits, in 1983 the US-Dutch-British IRAS inaugurated space-based infrared astronomy by performing the first-ever all-sky survey at infrared wavelengths. The resulting map of the infrared sky pinpointed some 350,000 infrared sources waiting to be explored by IRAS successors. In 1979 IRAS was in a stage of planning and the expected results from IRAS led to the first proposal for ISO made to ESA in the same year. With the rapid improvements in infrared detector-technology, ISO was to provide detailed observations for some 30,000 infrared sources with much improved sensitivity, ISO was to perform 1000 times better in sensitivity and 100 times better in angular resolution at 12 micrometres compared to IRAS. A number of follow-up studies resulted in the selection of ISO as the installment for the ESA Scientific Programme in 1983. Next came a Call for Experiment and Mission Scientist Proposals to the scientific community, the four instruments chosen were developed by teams of researchers from France, Germany, the Netherlands and United Kingdom. Final assembly took place at the Cannes Mandelieu Space Center, the basic design of ISO was strongly influenced by that of its immediate predecessor. Like IRAS, ISO was composed of two components, Payload module, composed of a large cryostat holding the telescope and the four scientific instruments. Service module, supports the activities of the module by providing electrical power, thermal control, attitude and orbit control. The payload module also held a sun shade, to prevent stray light from reaching the telescope. The latter were part of the Attitude and Orbit Control Subsystem which provided three-axis stabilisation of ISO with an accuracy of one arc second. It consisted of Sun and Earth sensors, the star trackers. An complementary reaction control system, using hydrazine propellant, was responsible for orbital direction, the complete satellite weighed just under 2500 kg, was 5.3 m high,3.6 m wide and measured 2.3 m in depth
25.
Hubble Space Telescope
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The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, with a 2. 4-meter mirror, Hubbles four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubbles orbit outside the distortion of Earths atmosphere allows it to take extremely high-resolution images, Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as determining the rate of expansion of the universe. The HST was built by the United States space agency NASA, the Space Telescope Science Institute selects Hubbles targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft. Space telescopes were proposed as early as 1923, Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. When finally launched in 1990, Hubbles main mirror was found to have been ground incorrectly, the optics were corrected to their intended quality by a servicing mission in 1993. Hubble is the telescope designed to be serviced in space by astronauts. After launch by Space Shuttle Discovery in 1990, five subsequent Space Shuttle missions repaired, upgraded, the fifth mission was canceled on safety grounds following the Columbia disaster. However, after spirited public discussion, NASA administrator Mike Griffin approved the fifth servicing mission, the telescope is operating as of 2017, and could last until 2030–2040. Its scientific successor, the James Webb Space Telescope, is scheduled for launch in 2018, the history of the Hubble Space Telescope can be traced back as far as 1946, to the astronomer Lyman Spitzers paper Astronomical advantages of an extraterrestrial observatory. In it, he discussed the two advantages that a space-based observatory would have over ground-based telescopes. First, the resolution would be limited only by diffraction, rather than by the turbulence in the atmosphere. Second, a telescope could observe infrared and ultraviolet light. Spitzer devoted much of his career to pushing for the development of a space telescope, space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel space program, oAO-1s battery failed after three days, terminating the mission. It was followed by OAO-2, which carried out observations of stars and galaxies from its launch in 1968 until 1972. The continuing success of the OAO program encouraged increasingly strong consensus within the community that the LST should be a major goal
26.
Near Infrared Camera and Multi-Object Spectrometer
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The Near Infrared Camera and Multi-Object Spectrometer is a scientific instrument for infrared astronomy, installed on the Hubble Space Telescope, operating from 1997 to 1999, and from 2002 to 2008. Images produced by NICMOS contain data from the part of the light spectrum. NICMOS was conceived and designed by the NICMOS Instrument Definition Team centered at Steward Observatory, University of Arizona, each optical channel contains a 256×256 pixel photodiode array of Hg0. 554Cd0. 446Te infrared detectors bonded to a sapphire substrate, read out in four independent 128×128 quadrants. NICMOS has been replaced by the infrared channel of Wide Field Camera 3 after its installation in 2009. NICMOS last worked in 2008, so WFC3 allowed NIR astronomy to continue in a powerful way, for example, the mirror is kept at a stable and relatively high temperature by heaters. The IR background flux collected by cooled focal plane IR instruments like NICMOS or WFC3 is dominated, at short wavelengths. Despite this, the combination of Hubbles mirror and NICMOS offered never-before seen levels of quality in near-infrared performance at that time. NICMOS in turn has been superseded by the Wide Field Camera 3, which has a much larger field of view. When conducting infrared measurements, it is necessary to keep the infrared detectors cooled to avoid having infrared interference from the instruments own thermal emissions. NICMOS contains a cryogenic dewar, that cooled its detectors to about 61 K, when NICMOS was installed in 1997, the dewar flask contained a 230-pound block of nitrogen ice. Due to a short that arose on March 4,1997, during the instrument commissioning. NICMOS was returned to service soon after SM 3B, a new software upload in September 2008 necessitated a brief shutdown of the NICMOS cooling system. Several attempts to restart the system were unsuccessful due to issues with the cryogenic circulator. After waiting more than six weeks for parts of the instrument to warm up, and theorized ice particles to sublimate from the circulating loop. An Anomaly Review Board was then convened by NASA, a successful restart at 13,30 EST on 16 December 2008 led to four days of cooler operations followed by another shutdown. The circulation flow rate to NICMOS was greatly reduced during this operating period confirming blockage in the circulation loop, continued operation at reduced flow rates would limit NICMOS science so plans for purging and refilling the circulation system with clean neon gas were developed by NASA. The circulation loop is equipped with an extra neon tank and remotely operated solenoid valves for on-orbit purge-fill operations, as of 2013, these purge-fill operations have not yet been performed. On June 18,2010, it was announced NICMOS would not be available for science during the latest proposal Cycle 18
27.
Starburst galaxy
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As such, the starburst nature of a galaxy is a phase, and one that typically occupies a brief period of a galaxys evolution. The majority of starburst galaxies are in the midst of a merger or close encounter with another galaxy, Starburst galaxies include M82, NGC 4038/NGC4039, and IC10. Starburst galaxies are defined by three interrelated factors, The rate at which the galaxy is currently converting gas into stars. The available quantity of gas from which stars can be formed, a comparison of the timescale on which star formation will consume the available gas with the age or rotation period of the galaxy. Commonly used definitions include, Continued star-formation where the current SFR would exhaust the available gas reservoir in much less than the age of the Universe, Continued star-formation where the current SFR would exhaust the available gas reservoir in much less than the dynamical timescale of the galaxy. The current SFR, normalised by the past-averaged SFR, is greater than unity. This ratio is referred to as the birthrate parameter, Starburst galaxies feature a large amount of cool molecular gas in a small volume. Galaxies in the midst of a starburst also frequently show tidal tails, classifying types of starburst galaxies is difficult since starburst galaxies do not represent a specific type in and of themselves. Starbursts can occur in disk galaxies, and irregular galaxies often exhibit knots of starburst spread throughout the irregular galaxy, nevertheless, astronomers typically classify starburst galaxies based on their most distinct observational characteristics. Some of the include, Blue compact galaxies. These galaxies are often low mass, low metallicity, dust-free objects, because they are dust-free and contain a large number of hot, young stars, they are often blue in optical and ultraviolet colours. It was initially thought that BCGs were genuinely young galaxies in the process of forming their first generation of stars, however, old stellar populations have been found in most BCGs, and it is thought that efficient mixing may explain the apparent lack of dust and metals. Most BCGs show signs of recent mergers and/or close interactions, well-studied BCGs include IZw18, ESO338-IG04 and Haro11. Blue compact dwarf galaxies are small compact galaxies, green Pea galaxies are small compact galaxies resembling primordial starbursts. They were found by citizen scientists taking part in the Galaxy Zoo project and these galaxies are generally extremely dusty objects. The ultraviolet radiation produced by the obscured star-formation is absorbed by the dust and this explains the extreme red colours associated with ULIRGs. It is not known for sure that the UV radiation is produced purely by star-formation, Wolf-Rayet galaxies, galaxies where a large portion of the bright stars are Wolf-Rayet stars. The Wolf-Rayet phases is a relatively short-lived phase in the life of stars, typically 10% of the total life-time of these stars
28.
Star formation
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Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as stellar nurseries or star-forming regions, fuse to form stars. It is closely related to formation, another branch of astronomy. Star formation theory, as well as accounting for the formation of a star, must also account for the statistics of binary stars. In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z =6.60, a spiral galaxy like the Milky Way contains stars, stellar remnants, and a diffuse interstellar medium of gas and dust. The interstellar medium consists of 10−4 to 106 particles per cm3 and is composed of roughly 70% hydrogen by mass. This medium has been enriched by trace amounts of heavier elements that were ejected from stars as they passed beyond the end of their main sequence lifetime. Higher density regions of the interstellar medium form clouds, or diffuse nebulae, in the dense nebulae where stars are produced, much of the hydrogen is in the molecular form, so these nebulae are called molecular clouds. These giant molecular clouds have densities of 100 particles per cm3, diameters of 100 light-years, masses of up to 6 million solar masses. About half the mass of the galactic ISM is found in molecular clouds and in the Milky Way there are an estimated 6,000 molecular clouds. The nearest nebula to the Sun where massive stars are being formed is the Orion nebula,1,300 ly away, however, lower mass star formation is occurring about 400–450 light years distant in the ρ Ophiuchi cloud complex. A more compact site of formation is the opaque clouds of dense gas and dust known as Bok globules. These can form in association with collapsing molecular clouds or possibly independently, the Bok globules are typically up to a light year across and contain a few solar masses. They can be observed as dark clouds silhouetted against bright emission nebulae or background stars, over half the known Bok globules have been found to contain newly forming stars. An interstellar cloud of gas will remain in equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force. Mathematically this is expressed using the theorem, which states that, to maintain equilibrium. If a cloud is massive enough that the gas pressure is insufficient to support it, the mass above which a cloud will undergo such collapse is called the Jeans mass. The Jeans mass depends on the temperature and density of the cloud and this coincides with the typical mass of an open cluster of stars, which is the end product of a collapsing cloud. In triggered star formation, one of several events occur to compress a molecular cloud
29.
Planetary system
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A planetary system is a set of gravitationally bound non-stellar objects in orbit around a star or star system. The Sun together with its system, which includes Earth, is known as the Solar System. The term exoplanetary system is used in reference to other planetary systems. There are at least 2,701 known planetary systems, including 610 systems consisting of planets as of 1 April 2017. These systems contain more than 3,607 known exoplanets, debris disks are also known to be common, though other objects are more difficult to observe. Of particular interest to astrobiology is the zone of planetary systems where planets could have surface liquid water. Historically, heliocentrism was opposed to geocentrism, the notion of a heliocentric Solar System, with the Sun at the center, is possibly first suggested in the Vedic literature of ancient India, which often refer to the Sun as the centre of spheres. Some interpret Aryabhattas writings in Āryabhaṭīya as implicitly heliocentric, the idea was first proposed in western philosophy and Greek astronomy as early as the 3rd century BC by Aristarchus of Samos, but had received no support from most other ancient astronomers. De revolutionibus orbium coelestium by Nicolaus Copernicus, published in 1543, was the first mathematically predictive heliocentric model of a planetary system and he was burned at the stake for his ideas by the Roman Inquisition. In the 18th century the same possibility was mentioned by Isaac Newton in the General Scholium that concludes his Principia and his theories gained traction through the 19th and 20th centuries despite a lack of supporting evidence. The first confirmed detection of an exoplanet was in 1992, with the discovery of several planets orbiting the pulsar PSR B1257+12. The first confirmed detection of exoplanets of a star was made in 1995. The frequency of detections has increased since then, particularly through advancements in methods of detecting extrasolar planets, planetary systems come from protoplanetary disks that form around stars as part of the process of star formation. During formation of a system much material is gravitationally scattered into far-flung orbits, Planets orbiting pulsars have been discovered, and pulsars are the remnants of the supernova explosions of high-mass stars. Planets found around pulsars may have formed as a result of pre-existing stellar companions that were almost entirely evaporated by the supernova blast, alternatively, planets may form in an accretion disk of fallback matter surrounding a pulsar. Fallback disks of matter that failed to orbit during a supernova may also form planets around black holes. As the star mass, planets that are not engulfed move further out from the star. Planets in evolved binary systems, Hagai B, perets,13 Jan 2011 Can Planets survive Stellar Evolution
30.
Vega
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It is relatively close at only 25 light-years from the Sun, and, together with Arcturus and Sirius, one of the most luminous stars in the Suns neighborhood. Vega has been studied by astronomers, leading it to be termed “arguably the next most important star in the sky after the Sun. ”Vega was the northern pole star around 12,000 BC. Vega was the first star other than the Sun to be photographed and it was one of the first stars whose distance was estimated through parallax measurements. Vega has served as the baseline for calibrating the photometric brightness scale, Vega has an unusually low abundance of the elements with a higher atomic number than that of helium. Vega is also a star that varies slightly in brightness. It is rotating rapidly with a velocity of 274 km/s at the equator and this is causing the equator to bulge outward because of centrifugal effects, and, as a result, there is a variation of temperature across the stars photosphere that reaches a maximum at the poles. From Earth, Vega is being observed from the direction of one of these poles, based on an observed excess emission of infrared radiation, Vega appears to have a circumstellar disk of dust. This dust is likely to be the result of collisions between objects in a debris disk, which is analogous to the Kuiper belt in the Solar System. Stars that display an infrared excess because of dust emission are termed Vega-like stars, α Lyrae is the stars Bayer designation. The traditional name Vega comes from a transliteration of the Arabic word wāqi‘ meaning falling or landing, via the phrase an-nasr al-wāqi‘. In 2016, the International Astronomical Union organized a Working Group on Star Names to catalog, the WGSNs first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN, which included Vega for this star. It is now so entered in the IAU Catalog of Star Names, astrophotography, the photography of celestial objects, began in 1840 when John William Draper took an image of the Moon using the daguerreotype process. On July 17,1850, Vega became the first star to be photographed, when it was imaged by William Bond and John Adams Whipple at the Harvard College Observatory, also with a daguerreotype. Henry Draper took the first photograph of a spectrum in August 1872 when he took an image of Vega. Similar lines had already identified in the spectrum of the Sun. In 1879, William Huggins used photographs of the spectra of Vega and these were later identified as lines from the Hydrogen Balmer series. Since 1943, the spectrum of this star has served as one of the anchor points by which other stars are classified. The distance to Vega can be determined by measuring its parallax shift against the stars as the Earth orbits the Sun
31.
Milky Way
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The Milky Way is the galaxy that contains our Solar System. The descriptive milky is derived from the appearance from Earth of the galaxy – a band of light seen in the night sky formed from stars that cannot be distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610, until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies, the Milky Way is a barred spiral galaxy with a diameter between 100,000 light-years and 180,000 light-years. The Milky Way is estimated to contain 100–400 billion stars, there are probably at least 100 billion planets in the Milky Way. The Solar System is located within the disk, about 26,000 light-years from the Galactic Center, on the edge of one of the spiral-shaped concentrations of gas. The stars in the inner ≈10,000 light-years form a bulge, the very center is marked by an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole. Stars and gases at a range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests much of the mass of the Milky Way does not emit or absorb electromagnetic radiation. This mass has been termed dark matter, the rotational period is about 240 million years at the position of the Sun. The Milky Way as a whole is moving at a velocity of approximately 600 km per second with respect to frames of reference. The oldest stars in the Milky Way are nearly as old as the Universe itself, the Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which is a component of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster. The Milky Way can be seen as a band of white light some 30 degrees wide arcing across the sky. Dark regions within the band, such as the Great Rift, the area of the sky obscured by the Milky Way is called the Zone of Avoidance. The Milky Way has a low surface brightness. Its visibility can be reduced by background light such as light pollution or stray light from the Moon. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be seen and it should be visible when the limiting magnitude is approximately +5.1 or better and shows a great deal of detail at +6.1
32.
Superfluidity
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Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without loss of kinetic energy. When stirred a superfluid forms cellular vortices that continue to rotate indefinitely, superfluidity occurs in two isotopes of helium when they are liquified by cooling to cryogenic temperatures. It is also a property of other exotic states of matter theorized to exist in astrophysics, high-energy physics. Superfluidity was originally discovered in liquid helium, by Pyotr Kapitsa and it has since been described through phenomenology and microscopic theories. In liquid helium-4, the superfluidity occurs at far higher temperatures than it does in helium-3, each atom of helium-4 is a boson particle, by virtue of its integer spin. A helium-3 atom is a particle, it can form bosons only by pairing with itself at much lower temperatures. The discovery of superfluidity in helium-3 was the basis for the award of the 1996 Nobel Prize in Physics and this process is similar to the electron pairing in superconductivity. Superfluidity in an ultracold fermionic gas was experimentally proven by Wolfgang Ketterle, such vortices had previously been observed in an ultracold bosonic gas using 87Rb in 2000, and more recently in two-dimensional gases. As early as 1999 Lene Hau created such a condensate using sodium atoms for the purpose of slowing light, with a double light-roadblock setup, we can generate controlled collisions between shock waves resulting in completely unexpected, nonlinear excitations. We have observed hybrid structures consisting of vortex rings embedded in dark solitonic shells, the vortex rings act as phantom propellers leading to very rich excitation dynamics. The idea that superfluidity exists inside neutron stars was first proposed by Arkady Migdal, superfluid vacuum theory is an approach in theoretical physics and quantum mechanics where the physical vacuum is viewed as superfluid. The ultimate goal of the approach is to develop scientific models that unify quantum mechanics with gravity and this makes SVT a candidate for the theory of quantum gravity and an extension of the Standard Model. Boojum Condensed matter physics Macroscopic quantum phenomena Quantum hydrodynamics Slow light Supersolid Guénault, annett, James F. Superconductivity, superfluids, and condensates. The Universe in a helium droplet
33.
Helium
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Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and its boiling point is the lowest among all the elements. Its abundance is similar to figure in the Sun and in Jupiter. This is due to the high nuclear binding energy of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and is believed to have formed during the Big Bang. Large amounts of new helium are being created by fusion of hydrogen in stars. Helium is named for the Greek god of the Sun, Helios and it was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by French astronomer Jules Janssen. Janssen is jointly credited with detecting the element along with Norman Lockyer, Janssen observed during the solar eclipse of 1868 while Lockyer observed from Britain. Lockyer was the first to propose that the line was due to a new element, the formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, who found helium emanating from the uranium ore cleveite. In 1903, large reserves of helium were found in gas fields in parts of the United States. Liquid helium is used in cryogenics, particularly in the cooling of superconducting magnets, a well-known but minor use is as a lifting gas in balloons and airships. As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre, on Earth it is relatively rare—5.2 ppm by volume in the atmosphere. Most terrestrial helium present today is created by the radioactive decay of heavy radioactive elements. Previously, terrestrial helium—a non-renewable resource, because once released into the atmosphere it readily escapes into space—was thought to be in short supply. The first evidence of helium was observed on August 18,1868, the line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India. This line was assumed to be sodium. He concluded that it was caused by an element in the Sun unknown on Earth, Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος
34.
Kelvin
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The kelvin is a unit of measure for temperature based upon an absolute scale. It is one of the seven units in the International System of Units and is assigned the unit symbol K. The kelvin is defined as the fraction 1⁄273.16 of the temperature of the triple point of water. In other words, it is defined such that the point of water is exactly 273.16 K. The Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Lord Kelvin, unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or typeset as a degree. The kelvin is the unit of temperature measurement in the physical sciences, but is often used in conjunction with the Celsius degree. The definition implies that absolute zero is equivalent to −273.15 °C, Kelvin calculated that absolute zero was equivalent to −273 °C on the air thermometers of the time. This absolute scale is known today as the Kelvin thermodynamic temperature scale, when spelled out or spoken, the unit is pluralised using the same grammatical rules as for other SI units such as the volt or ohm. When reference is made to the Kelvin scale, the word kelvin—which is normally a noun—functions adjectivally to modify the noun scale and is capitalized, as with most other SI unit symbols there is a space between the numeric value and the kelvin symbol. Before the 13th CGPM in 1967–1968, the unit kelvin was called a degree and it was distinguished from the other scales with either the adjective suffix Kelvin or with absolute and its symbol was °K. The latter term, which was the official name from 1948 until 1954, was ambiguous since it could also be interpreted as referring to the Rankine scale. Before the 13th CGPM, the form was degrees absolute. The 13th CGPM changed the name to simply kelvin. Its measured value was 7002273160280000000♠0.01028 °C with an uncertainty of 60 µK, the use of SI prefixed forms of the degree Celsius to express a temperature interval has not been widely adopted. In 2005 the CIPM embarked on a program to redefine the kelvin using a more experimentally rigorous methodology, the current definition as of 2016 is unsatisfactory for temperatures below 20 K and above 7003130000000000000♠1300 K. In particular, the committee proposed redefining the kelvin such that Boltzmanns constant takes the exact value 6977138065049999999♠1. 3806505×10−23 J/K, from a scientific point of view, this will link temperature to the rest of SI and result in a stable definition that is independent of any particular substance. From a practical point of view, the redefinition will pass unnoticed, the kelvin is often used in the measure of the colour temperature of light sources. Colour temperature is based upon the principle that a black body radiator emits light whose colour depends on the temperature of the radiator, black bodies with temperatures below about 7003400000000000000♠4000 K appear reddish, whereas those above about 7003750000000000000♠7500 K appear bluish
35.
Celsius
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Celsius, also known as centigrade, is a metric scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world and it is named after the Swedish astronomer Anders Celsius, who developed a similar temperature scale. The degree Celsius can refer to a temperature on the Celsius scale as well as a unit to indicate a temperature interval. Before being renamed to honour Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps. The scale is based on 0° for the point of water. This scale is widely taught in schools today, by international agreement the unit degree Celsius and the Celsius scale are currently defined by two different temperatures, absolute zero, and the triple point of VSMOW. This definition also precisely relates the Celsius scale to the Kelvin scale, absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. The temperature of the point of water is defined as precisely 273.16 K at 611.657 pascals pressure. This definition fixes the magnitude of both the degree Celsius and the kelvin as precisely 1 part in 273.16 of the difference between absolute zero and the point of water. Thus, it sets the magnitude of one degree Celsius and that of one kelvin as exactly the same, additionally, it establishes the difference between the two scales null points as being precisely 273.15 degrees. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the point of ice is essentially unaffected by pressure. He also determined with precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the point of his temperature scale, being the boiling point. This pressure is known as one standard atmosphere, the BIPMs 10th General Conference on Weights and Measures later defined one standard atmosphere to equal precisely 1013250dynes per square centimetre. On 19 May 1743 he published the design of a mercury thermometer, in 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus reversed Celsiuss scale. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden, since the 19th century, the scientific and thermometry communities worldwide referred to this scale as the centigrade scale. Temperatures on the scale were often reported simply as degrees or. More properly, what was defined as centigrade then would now be hectograde.2 gradians, for scientific use, Celsius is the term usually used, with centigrade otherwise continuing to be in common but decreasing use, especially in informal contexts in English-speaking countries
36.
Fahrenheit
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Fahrenheit is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit, after whom the scale is named. It uses the degree Fahrenheit as the unit, several accounts of how he originally defined his scale exist. The lower defining point,0 °F, was established as the temperature of a solution of brine made from parts of ice. Further limits were established as the point of ice and his best estimate of the average human body temperature. All other countries in the world now use the Celsius scale, defined since 1954 by absolute zero being −273.15 °C, on the Fahrenheit scale, the freezing point of water is 32 degrees Fahrenheit and the boiling point is 212 °F. This puts the boiling and freezing points of water exactly 180 degrees apart, therefore, a degree on the Fahrenheit scale is 1⁄180 of the interval between the freezing point and the boiling point. On the Celsius scale, the freezing and boiling points of water are 100 degrees apart, a temperature interval of 1 °F is equal to an interval of 5⁄9 degrees Celsius. The Fahrenheit and Celsius scales intersect at −40°, absolute zero is −273.15 °C or −459.67 °F. For an exact conversion, the formulas can be applied. Again, f is the value in Fahrenheit and c the value in Celsius, f °Fahrenheit to c °Celsius, C °Celsius to f °Fahrenheit, −40 = f. Fahrenheit proposed his temperature scale in 1724, basing it on two points of temperature. In his initial scale, the point is determined by placing the thermometer in a mixture of ice, water. This is a mixture which stabilizes its temperature automatically, that stable temperature was defined as 0 °F. The second point,96 degrees, was approximately the human bodys temperature, in any case, the definition of the Fahrenheit scale has changed since. According to a letter Fahrenheit wrote to his friend Herman Boerhaave, his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømers scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, Fahrenheit multiplied each value by four in order to eliminate fractions and increase the granularity of the scale. Fahrenheit observed that water boils at about 212 degrees using this scale, under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water is exactly 32 °F, and the boiling point is exactly 212 °F or 180 degrees higher. It is for this reason that human body temperature is approximately 98° on the revised scale
37.
Evaporation
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Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase, steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, on average, a fraction of the molecules in a glass of water have enough heat energy to escape from the liquid. The water in the glass will be cooled by the evaporation until an equilibrium is reached where the air supplies the amount of heat removed by the evaporating water, in an enclosed environment the water would evaporate until the air is saturated. With sufficient temperature, the liquid would turn into vapor quickly, when the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with energy to escape. Evaporation is an part of the water cycle. The sun drives evaporation of water from oceans, lakes, moisture in the soil, in hydrology, evaporation and transpiration are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor, when only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, as the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases. This phenomenon is also called evaporative cooling and this is why evaporating sweat cools the human body. Evaporation also tends to proceed quickly with higher flow rates between the gaseous and liquid phase and in liquids with higher vapor pressure. For example, laundry on a line will dry more rapidly on a windy day than on a still day. Three key parts to evaporation are heat, atmospheric pressure, on a molecular level, there is no strict boundary between the liquid state and the vapor state. Instead, there is a Knudsen layer, where the phase is undetermined, because this layer is only a few molecules thick, at a macroscopic scale a clear phase transition interface cannot be seen. It is just that the process is slower and thus significantly less visible. If evaporation takes place in an area, the escaping molecules accumulate as a vapor above the liquid. Many of the return to the liquid, with returning molecules becoming more frequent as the density
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