1.
Buffalo, New York
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Buffalo is a city in western New York state and the county seat of Erie County, on the eastern shores of Lake Erie at the head of the Niagara River. As of 2014, Buffalo is New York states 2nd-most populous city after New York City, the metropolitan area has a population of 1.13 million. After an economic downturn in the half of the 20th century, Buffalos economy has transitioned to sectors that include financial services, technology, biomedical engineering. Residents of Buffalo are called Buffalonians, the citys nicknames include The Queen City, The Nickel City and The City of Good Neighbors. The city of Buffalo received its name from a creek called Buffalo Creek. British military engineer Captain John Montresor made reference to Buffalo Creek in his journal of 1764, there are several theories regarding how Buffalo Creek received its name. In 1804, as principal agent opening the area for the Holland Land Company, Joseph Ellicott, designed a radial street and grid system that branches out from downtown like bicycle spokes similar to the street system he used in the nations capital. Although Ellicott named the settlement New Amsterdam, the name did not catch on, during the War of 1812, on December 30,1813, Buffalo was burned by British forces. The George Coit House 1818 and Samuel Schenck House 1823 are currently the oldest houses within the limits of the City of Buffalo, on October 26,1825, the Erie Canal was completed with Buffalo a port-of-call for settlers heading westward. At the time, the population was about 2,400, the Erie Canal brought about a surge in population and commerce, which led Buffalo to incorporate as a city in 1832. In 1845, construction began on the Macedonia Baptist Church, an important meeting place for the abolitionist movement, Buffalo was a terminus point of the Underground Railroad with many fugitive slaves crossing the Niagara River to Fort Erie, Ontario in search of freedom. During the 1840s, Buffalos port continued to develop, both passenger and commercial traffic expanded with some 93,000 passengers heading west from the port of Buffalo. Grain and commercial goods shipments led to repeated expansion of the harbor, in 1843, the worlds first steam-powered grain elevator was constructed by local merchant Joseph Dart and engineer Robert Dunbar. Darts Elevator enabled faster unloading of lake freighters along with the transshipment of grain in bulk from barges, canal boats, by 1850, the citys population was 81,000. At the dawn of the 20th century, local mills were among the first to benefit from hydroelectric power generated by the Niagara River, the city got the nickname City of Light at this time due to the widespread electric lighting. It was also part of the revolution, hosting the brass era car builders Pierce Arrow. President William McKinley was shot and mortally wounded by an anarchist at the Pan-American Exposition in Buffalo on September 6,1901, McKinley died in the city eight days later and Theodore Roosevelt was sworn in at the Wilcox Mansion as the 26th President of the United States. The Great Depression of 1929–39 saw severe unemployment, especially working class men
2.
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
3.
University of Southern California
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The University of Southern California is a private research university founded in 1880 with its main campus in Los Angeles, California. As Californias oldest private university, USC has historically educated a large number of the regions business leaders. In recent decades, the university has also leveraged its location in Los Angeles to establish relationships with research and cultural institutions throughout Asia, an engine for economic activity, USC contributes $8 billion annually to the economy of the Los Angeles metropolitan area and California. For the 2014–15 academic year, there were 18,740 students enrolled in undergraduate programs. USC also has 23,729 graduate and professional students in a number of different programs, including business, law, engineering, social work, and medicine. The university is one of the top fundraising institutions in the world, consistently ranking among the top 3 in external contributions, multiple academic rankings list the University of Southern California as being among the top 25 universities in the United States. With an acceptance rate of 16 percent, USC is also among the most selective academic institutions in the nation. USC maintains a tradition of innovation and entrepreneurship, with alumni having founded companies such as Lucasfilm, Myspace, Salesforce. com, Intuit, Qualcomm, Box, Tinder. As of 2014, the university has produced the fourth largest number of billionaire alumni out of all institutions in the world. USC is home to the world’s most powerful computer, which is presently housed in a super-cooled. The only other commercially available quantum computing system is operated jointly by NASA, USC was also one of the earliest nodes on ARPANET and is the birthplace of the Domain Name System. Other technologies invented at USC include DNA computing, dynamic programming, image compression, VoIP, USC sponsors a variety of intercollegiate sports and competes in the National Collegiate Athletic Association as a member of the Pac-12 Conference. Members of the teams, the Trojans, have won 102 NCAA team championships, ranking them third in the nation. Trojan athletes have won 288 medals at the Olympic games, more than any university in the United States. If USC were a country, its athletes would have received the 12th-most Olympic gold medals in history. In 1969, it joined the Association of American Universities, the University of Southern California was founded following the efforts of Judge Robert M. Hellman. The three donated 308 lots of land to establish the campus and provided the seed money for the construction of the first buildings. Originally operated in affiliation with the Methodist Church, the school mandated from the start that no student would be denied admission because of race, the university is no longer affiliated with any church, having severed formal ties in 1952
4.
Astronomy
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Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry, in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, moons, stars, galaxies, and comets, while the phenomena include supernovae explosions, gamma ray bursts, more generally, all astronomical phenomena that originate outside Earths atmosphere are within the purview of astronomy. A related but distinct subject, physical cosmology, is concerned with the study of the Universe as a whole, Astronomy is the oldest of the natural sciences. The early civilizations in recorded history, such as the Babylonians, Greeks, Indians, Egyptians, Nubians, Iranians, Chinese, during the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the results and observations being used to confirm theoretical results. Astronomy is one of the few sciences where amateurs can play an active role, especially in the discovery. Amateur astronomers have made and contributed to many important astronomical discoveries, Astronomy means law of the stars. Astronomy should not be confused with astrology, the system which claims that human affairs are correlated with the positions of celestial objects. Although the two share a common origin, they are now entirely distinct. Generally, either the term astronomy or astrophysics may be used to refer to this subject, however, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics. Few fields, such as astrometry, are purely astronomy rather than also astrophysics, some titles of the leading scientific journals in this field includeThe Astronomical Journal, The Astrophysical Journal and Astronomy and Astrophysics. In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye, in some locations, early cultures assembled massive artifacts that possibly had some astronomical purpose. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye, most of early astronomy actually consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, and the nature of the Sun, Moon, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the model of the Universe, or the Ptolemaic system. The Babylonians discovered that lunar eclipses recurred in a cycle known as a saros
5.
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
6.
Palomar Observatory
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Palomar Observatory is an astronomical observatory located in San Diego County, California, United States,145 kilometers southeast of Los Angeles, California, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology located in Pasadena, research time is granted to Caltech and its research partners, which include the Jet Propulsion Laboratory and Cornell University. The observatory operates several telescopes, including the famous 200-inch Hale Telescope, astronomer George Ellery Hale, whose vision created the Palomar Observatory, built the worlds largest telescope four times. He published an article in the April 1928 issue of Harpers Magazine called The Possibilities of Large Telescopes, Hale hoped that the American people would understand and support his project. Hale followed this article with a letter to the International Education Board of the Rockefeller Foundation dated April 28,1928, in his letter, Hale stated, No method of advancing science is so productive as the development of new and more powerful instruments and methods of research. The 200-inch telescope is named after astronomer George Hale and it was built by Caltech with a $6 million grant from the Rockefeller Foundation, using a Pyrex blank manufactured by Corning Glass Works. Anderson was the project manager assigned in the early 1940s. The telescope saw first light January 26,1949 targeting NGC2261, the American astronomer Edwin Powell Hubble, perhaps the most important observer of the 20th century, was given the honor of being the first astronomer to use the telescope. Astronomers using the Hale Telescope have discovered distant objects at the edges of the universe called quasars and have given us the first direct evidence of stars in distant galaxies. They have studied the structure and chemistry of intergalactic clouds, leading to an understanding of the synthesis of elements in the universe, porter worked on the designs in collaboration with many engineers and Caltech committee members. The gleaming white building on Palomar Mountain that houses the 200–inch Hale Telescope is considered by many to be The Cathedral of Astronomy, the 200-inch Hale Telescope was first proposed in 1928 and has been operational since 1948. It was the largest telescope in the world for 45 years, a 60-inch reflecting telescope is located in the Oscar Mayer Building. It was dedicated in 1970 to take some of the load off of the Hale Telescope and this telescope was used to discover the first brown dwarf star. The 48-inch Samuel Oschin Telescope was started in 1938 and installed in 1948 and it was initially called the 48–inch Schmidt, and was dedicated to Samuel Oschin in 1986. The dwarf planet Eris was discovered using this instrument, the existence of Eris triggered the discussions in the international astronomy community that led to Pluto being re-classified as a dwarf planet. An 18-inch Schmidt camera became the first operational telescope at the Palomar in 1936, in the 1930s, Fritz Zwicky, a Caltech astronomer, discovered over 100 supernovae in other galaxies with this telescope and gathered the first evidence for dark matter. Comet Shoemaker-Levy 9 was discovered with this instrument in 1993 and it has since been retired and is on display at the small museum/visitor center. The Palomar Testbed Interferometer was an instrument that permitted astronomers to make very high resolution measurements of the sizes
7.
Space Telescope Science Institute
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The Space Telescope Science Institute is the science operations center for the Hubble Space Telescope and for the James Webb Space Telescope. There are approximately 100 Ph. D. scientists working at STScI,15 of which are ESA staff who are on assignment to the HST project, the total STScI staff consists of about 450 people. STScI operates its missions on behalf of NASA, the astronomy community. The ground system development activities create and maintain the systems that are needed to provide these services to the astronomy community. STScIs public outreach activities provide a range of information, on-line media, and programs for formal educators, planetariums and science museums. STScIs award-winning public outreach websites receive millions of hits per month, STScI also serves as a source of guidance to NASA on a range of optical and UV space astrophysics issues. The STScI conducts all activities required to select, schedule, the first step in this process is to support the annual community-led selection of the scientific programs that will be performed with HST. This begins with publishing of the annual Call for Proposals, which specifies the currently supported science instrument capabilities, proposal requirements, anyone is eligible to submit a proposal. All proposals are critically peer-reviewed by the Time Allocation Committee, the TAC consists of about 100 members of the U. S. and international astronomical community, selected to represent a broad range of research expertise needed to evaluate the proposals. Each proposal cycle typically involves reviewing 700 to 1100 proposals, only 15 - 20% of these proposals will eventually be selected for implementation. The TAC reviews several categories of observing time, as well as proposals for archival, theoretical, STScI provides all technical and logistical support for these activities. The annual cycle of proposal calls was occasionally altered in duration in years when a HST servicing mission was scheduled, proposers fortunate enough to be awarded telescope time, referred to as General Observers, must then provide detailed requirements needed to schedule and implement their observing programs. This information is provided to STScI on what is called a Phase II proposal, the Phase II proposal specifies instrument operation modes, exposure times, telescope orientations, and so on. In addition, the STScI staff carries out all the necessary to implement each specific program. Adjustments can be made to both long-range and weekly plans in response to Targets of Opportunity, the STScI uses the Min-conflicts algorithm to schedule observation time on the telescope. Flight Operations consists of the support and monitoring of HST functions in real-time. Real-time daily flight operations for HST include about 4 command load uplinks, about 10 data downlinks, real-time operations are staffed around the clock. Flight operations activities for HST are done at NASAs GSFC in Greenbelt, Science data from HST arrive at the STScI a few hours after being downlinked from TDRSS and subsequently passing through a data capture facility at NASAs Goddard Space Flight Center
8.
Applied Physics Laboratory
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The, located in Howard County, Maryland, near Laurel and Columbia, is a not-for-profit, university-affiliated research center employing 6,000 people. APL is primarily a defense contractor and it serves as a technical resource for the Department of Defense, NASA, and other government agencies. The Lab is a research and development organization rather than an academic division of Johns Hopkins University. Hopkins Whiting School of Engineering offers part-time graduate programs through its Engineering for Professionals program, courses are taught at seven locations in the Baltimore-Washington Metropolitan Area, including the APL Education Center. Its founding director was Merle Anthony Tuve, the Laboratory succeeded in developing the variable-time proximity fuze that played a significant role in the Allied victory. In response to the success, the APL created the MK57 gun director in 1944. Pleased with the APLs work, the Navy then tasked it with the mission to find a way to negate guided missile threats, from there on, the APL became very involved in wartime research. Expected to disband at the end of the war, APL instead became involved in the development of guided missile technology for the Navy. At governmental request, the University continued to maintain the Laboratory as a public service, APL was originally located in Silver Spring, Maryland in a used-car garage at the former Wolf Motor Company building at 8621 Georgia Avenue. APL moved to Laurel beginning in 1954, with the construction of a two million dollar building and a $700,000 wing expansion in 1956, the final staff transitioned to the new facility in 1975. Before moving to Laurel, APL also maintained the Forest Grove Station, north of Silver Spring on Georgia Avenue near todays Forest Glen Metro, the Forest Grove Station was vacated and torn down in 1963 and flight simulations were moved to Laurel. The Laboratorys name comes from its origins in World War II, about half of the technical staff are engineers, and 25% have computer science and math degrees. APL conducts programs in fundamental and applied research, exploratory and advanced development, test and evaluation, in 1965, the US Army contracted with APL to develop and implement a test and evaluation program for the Pershing missile systems. In 1990, APL became involved with Operation Desert Storm and was involved in the Gulf Crisis Room among other efforts, in the same decade, APL, along with Johns Hopkins University, developed an algorithm that allowed for automatic mammogram analysis. In 2014, the APL made history with the use of Modular Prosthetic Limbs by a bilateral shoulder-level amputee. APL used pattern recognition algorithms to track which muscles were contracting, the Lab is currently developing the Solar Probe Plus mission to probe the outer corona of the Sun. Located on a 399-acre campus, APL is also home to a Johns Hopkins graduate program in engineering and applied sciences, the U. S. Navy continues to be APLs primary long-term sponsor. The Laboratory performs work for the Missile Defense Agency, the Department of Homeland Security, intelligence agencies, the Defense Advanced Research Projects Agency, the Laboratory supports NASA through space science, spacecraft design and fabrication, and mission operations
9.
Minor planet
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A minor planet is an astronomical object in direct orbit around the Sun that is neither a planet nor exclusively classified as a comet. Minor planets can be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, as of 2016, the orbits of 709,706 minor planets were archived at the Minor Planet Center,469,275 of which had received permanent numbers. The first minor planet to be discovered was Ceres in 1801, the term minor planet has been used since the 19th century to describe these objects. The term planetoid has also used, especially for larger objects such as those the International Astronomical Union has called dwarf planets since 2006. Historically, the asteroid, minor planet, and planetoid have been more or less synonymous. This terminology has become complicated by the discovery of numerous minor planets beyond the orbit of Jupiter. A Minor planet seen releasing gas may be classified as a comet. Before 2006, the IAU had officially used the term minor planet, during its 2006 meeting, the IAU reclassified minor planets and comets into dwarf planets and small Solar System bodies. Objects are called dwarf planets if their self-gravity is sufficient to achieve hydrostatic equilibrium, all other minor planets and comets are called small Solar System bodies. The IAU stated that the minor planet may still be used. However, for purposes of numbering and naming, the distinction between minor planet and comet is still used. Hundreds of thousands of planets have been discovered within the Solar System. The Minor Planet Center has documented over 167 million observations and 729,626 minor planets, of these,20,570 have official names. As of March 2017, the lowest-numbered unnamed minor planet is 1974 FV1, as of March 2017, the highest-numbered named minor planet is 458063 Gustavomuler. There are various broad minor-planet populations, Asteroids, traditionally, most have been bodies in the inner Solar System. Near-Earth asteroids, those whose orbits take them inside the orbit of Mars. Further subclassification of these, based on distance, is used, Apohele asteroids orbit inside of Earths perihelion distance. Aten asteroids, those that have semi-major axes of less than Earths, Apollo asteroids are those asteroids with a semimajor axis greater than Earths, while having a perihelion distance of 1.017 AU or less. Like Aten asteroids, Apollo asteroids are Earth-crossers, amor asteroids are those near-Earth asteroids that approach the orbit of Earth from beyond, but do not cross it
10.
Astronomer
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An astronomer is a scientist in the field of astronomy who concentrates their studies on a specific question or field outside of the scope of Earth. They look at stars, planets, moons, comets and galaxies, as well as other celestial objects — either in observational astronomy. Examples of topics or fields astronomers work on include, planetary science, solar astronomy, there are also related but distinct subjects like physical cosmology which studies the Universe as a whole. Astronomers usually fit into two types, Observational astronomers make direct observations of planets, stars and galaxies, and analyze the data, theoretical astronomers create and investigate models of things that cannot be observed. They use this data to create models or simulations to theorize how different celestial bodies work, there are further subcategories inside these two main branches of astronomy such as planetary astronomy, galactic astronomy or physical cosmology. Today, that distinction has disappeared and the terms astronomer. Professional astronomers are highly educated individuals who typically have a Ph. D. in physics or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although quite often have other duties such as teaching, building instruments. The number of astronomers in the United States is actually quite small. The American Astronomical Society, which is the organization of professional astronomers in North America, has approximately 7,000 members. This number includes scientists from other such as physics, geology. The International Astronomical Union comprises almost 10,145 members from 70 different countries who are involved in research at the Ph. D. level. Before CCDs, photographic plates were a method of observation. Modern astronomers spend relatively little time at telescopes usually just a few weeks per year, analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes, most universities also have outreach programs including public telescope time and sometimes planetariums as a public service to encourage interest in the field. Those who become astronomers usually have a background in maths, sciences. Taking courses that teach how to research, write and present papers are also invaluable, in college/university most astronomers get a Ph. D. in astronomy or physics. Keeping in mind how few there are it is understood that graduate schools in this field are very competitive
11.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
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Mount Wilson Observatory
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The Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 1, 740-metre peak in the San Gabriel Mountains near Pasadena, the observatory was conceived and founded by George Ellery Hale, who had previously built the 1 meter telescope at the Yerkes Observatory, then the worlds largest telescope. The Mount Wilson Solar Observatory was first funded by the Carnegie Institution of Washington in 1904, among the conditions of the lease was that it allow public access. There are three solar telescopes at Mount Wilson Observatory, today, just one of these telescopes, the 60 foot Solar Tower, is still used for solar research. The Snow Solar Telescope was the first telescope installed at the fledgling Mount Wilson Solar Observatory and it was the worlds first permanently mounted solar telescope. Solar telescopes had previously been portable so they could be taken to solar eclipses around the world, the telescope was donated to Yerkes Observatory by Helen Snow of Chicago. George Ellery Hale, then director of Yerkes, had the telescope brought to Mount Wilson to put it into service as a scientific instrument. Stellar research soon followed as the brightest stars could have their spectra recorded with very long exposures on glass plates, today the Snow solar telescope is mostly used by undergraduate students who get hands on training in solar physics and spectroscopy. It was also used publicly for the May 9,2016 transit of Mercury across the face of the sun, the 60-foot Solar Tower soon built on the work started at the Snow telescope. At its completion in 1908, the tower design of the 60 foot focal length solar telescope allowed much higher resolution of the solar image. The higher resolution came from situating the optics higher above the ground, on June 25,1908, Hale would record Zeeman splitting in the spectrum of a sunspot, showing for the first time that magnetic fields existed somewhere besides the earth. A later discovery was of the polarity in sunspots of the new solar cycle of 1912. The success of the 60 foot Tower prompted Hale to pursue yet another, taller tower telescope, in the 1960s, Robert Leighton discovered the sun had a 5-minute oscillation and the field of heliosiesmology was born. The 60 foot Tower is operated by the Department of Physics, the 150-foot focal length solar tower expanded on the solar tower design with its tower-in-a-tower design. An inner tower supports the optics above, while an outer tower and this design allowed complete isolation of the optics from the effect of wind swaying the tower. Two mirrors feed sunlight to a 12-inch lens which focuses light down at the ground floor and it was first completed in 1910, but unsatisfactory optics caused a two-year delay before a suitable doublet lens was installed. Research included solar rotation, sunspot polarities, daily sunspot drawings, the solar telescope would be the worlds largest for 50 years until the McMath-Pierce Solar telescope was completed at Kitt Peak in Arizona in 1962. In 1985, UCLA took over operation of the tower from the Carnegie Observatories after it was decided to stop funding the observatory
13.
Centaur (minor planet)
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Centaurs are minor planets with a semi-major axis between those of the outer planets. They have unstable orbits that cross or have crossed the orbits of one or more of the giant planets, Centaurs typically behave with characteristics of both asteroids and comets. They are named after the centaurs that were a mixture of horse. It has been estimated there are around 44,000 centaurs in the Solar System with diameters larger than 1 km. The first centaur to be discovered, under the definition of the Jet Propulsion Laboratory, however, they were not recognized as a distinct population until the discovery of 2060 Chiron in 1977. The largest confirmed centaur is 10199 Chariklo, which at 260 km in diameter is as big as a mid-sized main-belt asteroid, however, the lost centaur 1995 SN55 may be somewhat larger. No centaur has been photographed up close, although there is evidence that Saturns moon Phoebe, imaged by the Cassini probe in 2004, in addition, the Hubble Space Telescope has gleaned some information about the surface features of 8405 Asbolus. As of 2008, three centaurs have been found to display comet-like comas, Chiron,60558 Echeclus, and 166P/NEAT, Chiron and Echeclus are therefore classified as both asteroids and comets. Other centaurs, such as 52872 Okyrhoe and 2012 CG, are suspected of having shown comas, any centaur that is perturbed close enough to the Sun is expected to become a comet. The generic definition of a centaur is a body that orbits the Sun between Jupiter and Neptune and crosses the orbits of one or more of the giant planets. Though nowadays the MPC often lists centaurs and scattered disc objects together as a single group, the Jet Propulsion Laboratory similarly defines centaurs as having a semi-major axis, a, between those of Jupiter and Neptune. In contrast, the Deep Ecliptic Survey defines centaurs using a classification scheme. These classifications are based on the change in behavior of the present orbit when extended over 10 million years. The DES defines centaurs as non-resonant objects whose instantaneous perihelia are less than the osculating semi-major axis of Neptune at any time during the simulation and this definition is intended to be synonymous with planet-crossing orbits and to suggest comparatively short lifetimes in the current orbit. The collection The Solar System Beyond Neptune defines objects with an axis between those of Jupiter and Neptune and a Jupiter – Tisserands parameter above 3. The JPL Small-Body Database lists 324 centaurs, there are an additional 65 trans-Neptunian objects with a perihelion closer than the orbit of Uranus. The Committee on Small Body Nomenclature of the International Astronomical Union has not formally weighed in on either side of the debate, thus far, only the binary objects Ceto and Phorcys and Typhon and Echidna have been named according to the new policy. Other objects caught between these differences in classification methods include 944 Hidalgo which was discovered in 1920 and is listed as a centaur in the JPL Small-Body Database
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Jupiter
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Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, Jupiter and Saturn are gas giants, the other two giant planets, Uranus and Neptune are ice giants. Jupiter has been known to astronomers since antiquity, the Romans named it after their god Jupiter. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium and it may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rotation, the planets shape is that of an oblate spheroid. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence, a prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere, Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a greater than that of the planet Mercury. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. In late February 2007, Jupiter was visited by the New Horizons probe, the latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4,2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa, Earth and its neighbor planets may have formed from fragments of planets after collisions with Jupiter destroyed those super-Earths near the Sun. Astronomers have discovered nearly 500 planetary systems with multiple planets, Jupiter moving out of the inner Solar System would have allowed the formation of inner planets, including Earth. Jupiter is composed primarily of gaseous and liquid matter and it is the largest of the four giant planets in the Solar System and hence its largest planet. It has a diameter of 142,984 km at its equator, the average density of Jupiter,1.326 g/cm3, is the second highest of the giant planets, but lower than those of the four terrestrial planets. Jupiters upper atmosphere is about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, a helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms. Thus, Jupiters atmosphere is approximately 75% hydrogen and 24% helium by mass, the atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, the outermost layer of the atmosphere contains crystals of frozen ammonia. The interior contains denser materials - by mass it is roughly 71% hydrogen, 24% helium, through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found
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Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers
16.
Comet
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A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces an atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of collections of ice, dust. The coma may be up to 15 times the Earths diameter, if sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° across the sky. Comets have been observed and recorded since ancient times by many cultures, Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars, hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition, Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma and the tail, however, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. As of November 2014 there are 5,253 known comets, however, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System is estimated to be one trillion. Roughly one comet per year is visible to the eye, though many of those are faint. Particularly bright examples are called Great Comets, the word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης, Κομήτης was derived from κομᾶν, which was itself derived from κόμη and was used to mean the tail of a comet. The astronomical symbol for comets is ☄, consisting of a disc with three hairlike extensions. The solid, core structure of a comet is known as the nucleus, cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen gases such as carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are described as dirty snowballs after Fred Whipples model
17.
Supernova
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This causes the sudden appearance of a new bright star, before slowly fading from sight over several weeks or months. Supernovae are more energetic than novae, in Latin, nova means new, referring astronomically to what appears to be a temporary new bright star. Adding the prefix super- distinguishes supernovae from ordinary novae, which are far less luminous, the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. It is pronounced /ˌsuːpərnoʊvə/ with the plural supernovae /ˌsuːpərnoʊviː/ or supernovas, only three Milky Way naked-eye supernova events have been observed during the last thousand years, though many have been seen in other galaxies using telescopes. The most recent directly observed supernova in the Milky Way was Keplers Supernova in 1604, Supernovae may expel much, if not all, of the material away from a star, at velocities up to 30,000 km/s or 10% of the speed of light. This drives an expanding and fast-moving shock wave into the interstellar medium, and in turn, sweeping up an expanding shell of gas and dust. Supernovae create, fuse and eject the bulk of the chemical elements produced by nucleosynthesis, Supernovae play a significant role in enriching the interstellar medium with the heavier atomic mass chemical elements. Furthermore, the shock waves from supernovae can trigger the formation of new stars. Supernova remnants are expected to accelerate a large fraction of primary cosmic rays. They are also potentially strong galactic sources of gravitational waves, in the second case, the core of a massive star may undergo sudden gravitational collapse, releasing gravitational potential energy as a supernova. While some observed supernovae are more complex than these two simplified theories, the astrophysical collapse mechanics have been established and accepted by most astronomers for some time, in Latin, Nova means new, referring astronomically to what appears to be a temporary new bright star. Adding the prefix super- distinguishes supernovae from ordinary novae, which are far less luminous, the word supernova was coined by Walter Baade and Fritz Zwicky in 1931. It is pronounced /ˌsuːpərnoʊvə/ with the plural supernovae /ˌsuːpərnoʊviː/ or supernovas, the earliest recorded supernova, SN185, was viewed by Chinese astronomers in 185 AD. The brightest recorded supernova was SN1006, which occurred in 1006 AD and was described in detail by Chinese, the widely observed supernova SN1054 produced the Crab Nebula. Johannes Kepler began observing SN1604 at its peak on October 17,1604 and it was the second supernova to be observed in a generation. There is some evidence that the youngest galactic supernova, G1. 9+0.3, occurred in the late 19th century, neither supernova was noted at the time. In the case of G1. 9+0.3, high extinction along the plane of the galaxy could have dimmed the event sufficiently to go unnoticed, the situation for Cassiopeia A is less clear. Infrared light echos have been detected showing that it was a type IIb supernova and was not in a region of especially high extinction, before the development of the telescope, there have only been five supernovae seen in the last millennium
18.
Samuel Oschin telescope
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The Samuel Oschin telescope is a 48-inch-aperture Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49. 75-inch Schmidt corrector plate and a 72-inch mirror, the instrument is strictly a camera, there is no provision for an eyepiece to look through it. It originally used 10- and 14-inch glass photographic plates, since the focal plane is curved, these plates had to be preformed in a special jig before being loaded into the camera. Construction on the Schmidt telescope began in 1939 and it was completed in 1948 and it was named the Samuel Oschin telescope in 1986. Before that it was just called the 48-inch Schmidt, the camera has been converted to use a CCD imager. This is a mosaic of 12 CCDs covering the field of view of the camera. The corrector plate was replaced using glass that is transparent to a wider range of wavelengths. The camera was originally hand-guided through one of two 10-inch-aperture refracting telescopes mounted on either side of the camera, the camera is now fully automated and remote-controlled. The data collected is transmitted over the High Performance Wireless Research and it is programmed and operated primarily from Pasadena, California, with no operator on site. In 2002, astronomer Jean Mueller approached Richard Ellis, the director of the Caltech Optical Observatories, Mueller was also rewarded by a visit to the Keck Observatory in Hawaii. The Oschin Telescope was responsible for the discovery of 90377 Sedna on 2003-11-14 and Eris, the peculiar Type Ia supernova SN 2002cx was discovered with the Oschin telescope on 2002 May 12.21 UT. Other discoveries include 90482 Orcus and 50000 Quaoar, both large trans-Neptune objects, in June 2011 it was reported the telescope discovered 6 supernovae located 8 billion light years from Earth whose composition lacks hydrogen. This is different from normal supernovae, and will contribute to the research of star formation. S, national Park Service Picture, c.1960 Edwin Hubble at the 48 Schmidt. Order comes to a universe, Caltech336, Vol.203
19.
Cosmology
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Cosmology is the study of the origin, evolution, and eventual fate of the universe. The term cosmology was first used in English in 1656 in Thomas Blounts Glossographia, religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation and eschatology. Physical cosmology is studied by scientists, such as astronomers and physicists, as well as philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Because of this scope with philosophy, theories in physical cosmology may include both scientific and non-scientific propositions, and may depend upon assumptions that can not be tested. Cosmology differs from astronomy in that the former is concerned with the Universe as a whole while the latter deals with individual celestial objects. Theoretical astrophysicist David N. Spergel has described cosmology as a science because when we look out in space. Physics and astrophysics have played a role in shaping the understanding of the universe through scientific observation. Physical cosmology was shaped through both mathematics and observation in an analysis of the whole universe, cosmogony studies the origin of the Universe, and cosmography maps the features of the Universe. In Diderots Encyclopédie, cosmology is broken down into uranology, aerology, geology, metaphysical cosmology has also been described as the placing of man in the universe in relationship to all other entities. Physical cosmology is the branch of physics and astrophysics that deals with the study of the physical origins and it also includes the study of the nature of the Universe on a large scale. In its earliest form, it was what is now known as celestial mechanics, greek philosophers Aristarchus of Samos, Aristotle, and Ptolemy proposed different cosmological theories. The geocentric Ptolemaic system was the theory until the 16th century when Nicolaus Copernicus. This is one of the most famous examples of epistemological rupture in physical cosmology, when Isaac Newton published the Principia Mathematica in 1687, he finally figured out how the heavens moved. A fundamental difference between Newtons cosmology and those preceding it was the Copernican principle—that the bodies on earth obey the same laws as all the celestial bodies. This was a crucial advance in physical cosmology. Physicists began changing the assumption that the Universe was static and unchanging, in 1922 Alexander Friedmann introduced the idea of an expanding universe that contained moving matter. In parallel to this approach to cosmology, one long-standing debate about the structure of the cosmos was coming to a climax. This difference of ideas came to a climax with the organization of the Great Debate on 26 April 1920 at the meeting of the U. S. National Academy of Sciences in Washington, D. C
20.
Fritz Zwicky
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Fritz Zwicky was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, in 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen dark matter, describing it as dunkle Materie. Fritz Zwicky was born in Varna, in the Principality of Bulgaria and his father, Fridolin, was a prominent industrialist in the Bulgarian city and also served as ambassador of Norway in Varna. The Zwicky House in Varna was designed and built by Fridolin Zwicky, fritzs mother, Franziska Vrček, was an ethnic Czech of the Austro-Hungarian Empire. Fritz was the oldest of the Zwicky familys three children, he had a brother named Rudolf and a sister, Leonie. Fritzs mother died in Varna in 1927, and his father Fridolin remained in Bulgaria until 1945 and his sister Leonie married a Bulgarian from Varna and spent her entire life in the city. In 1904, at the age of six, Fritz was sent to his grandparents in the familys ancestral canton in Glarus, Switzerland, to study commerce. His interests shifted to math and physics and he received an education in mathematics and experimental physics at the Swiss Federal Polytechnic, located in Zurich. He was responsible for positing numerous cosmological theories that have a impact on the understanding of our universe today. He was the first to coin the term supernova during his fostering the concept of neutron stars, Zwicky was a lone wolf and did all of his own mathematical work. He intended to write an autobiography titled, Operation Lone Wolf and it would be five years later when Oppenheimer would publish his landmark paper announcing neutron stars. He developed some of the earliest jet engines and holds over 50 patents, many in jet propulsion, and is the inventor of the Underwater Jet, the Two Piece Jet Thrust Motor and Inverted Hydro Pulse. In April 1932, Fritz Zwicky married Dorothy Vernon Gates, a member of a prominent local family and her money was instrumental in the funding of the Palomar Observatory during the Great Depression. Nicholas Roosevelt, cousin of President Theodore Roosevelt, was his brother-in-law by marriage to Tirzah Gates, Zwicky and Dorothy divorced amicably in 1941. In 1947 Zwicky was married in Switzerland to Anna Margaritha Zurcher, Zwicky died in Pasadena on February 8,1974, and was buried in Mollis, Switzerland. He is remembered as both a genius and a curmudgeon, one of his favorite insults was to refer to people he did not approve of as spherical bastards, because, he explained, they were bastards no matter which way you looked at them. A recent biography in English was published by the Fritz Zwicky Foundation, Alfred Stöckli & Roland Müller, a review of the book is available from Acta Morphologica Generalis. Fritz Zwicky was a prolific scientist and made important contributions in areas of astronomy
21.
Type Ia supernova
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A type Ia supernova is a type of supernova that occurs in binary systems in which one of the stars is a white dwarf. The other star can be anything from a giant star to a smaller white dwarf. Physically, carbon–oxygen white dwarfs with a low rate of rotation are limited to below 1.44 solar masses, beyond this, they re-ignite and in some cases trigger a supernova explosion. If a white dwarf accretes mass from a binary companion. If the white dwarf merges with another white dwarf, it will exceed the limit and begin to collapse. This type Ia category of supernovae produces consistent peak luminosity because of the mass of white dwarfs that explode via the accretion mechanism. In May 2015, NASA reported that the Kepler space observatory observed KSN 2011b, details of the pre-nova moments may help scientists better judge the quality of Type Ia supernovae as standard candles, which is an important link in the argument for dark energy. The Type Ia supernova is a sub-category in the Minkowski-Zwicky supernova classification scheme, there are several means by which a supernova of this type can form, but they share a common underlying mechanism. The current view among astronomers who model Type Ia supernova explosions, however, is that limit is never actually attained. At some point in this phase, a deflagration flame front is born. The details of the ignition are still unknown, including the location, oxygen fusion is initiated shortly thereafter, but this fuel is not consumed as completely as carbon. Once fusion has begun, the temperature of the white dwarf starts to rise, a main sequence star supported by thermal pressure would expand and cool which automatically counterbalances an increase in thermal energy. However, degeneracy pressure is independent of temperature, the dwarf is unable to regulate the fusion process in the manner of normal stars. The flame accelerates dramatically, in due to the Rayleigh–Taylor instability. It is still a matter of debate whether this flame transforms into a supersonic detonation from a subsonic deflagration. The star explodes violently and releases a wave in which matter is typically ejected at speeds on the order of 5, 000–20000 km/s. The energy released in the explosion causes an extreme increase in luminosity. The typical visual absolute magnitude of Type Ia supernovae is Mv = −19.3, the theory of this type of supernovae is similar to that of novae, in which a white dwarf accretes matter more slowly and does not approach the Chandrasekhar limit
22.
Standard candle
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The cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an object is possible only for those objects that are close enough to Earth. The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at distances and methods that work at larger distances. Several methods rely on a candle, which is an astronomical object that has a known luminosity. The ladder analogy arises because no single technique can measure distances at all ranges encountered in astronomy, instead, one method can be used to measure nearby distances, a second can be used to measure nearby to intermediate distances, and so on. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung, at the base of the ladder are fundamental distance measurements, in which distances are determined directly, with no physical assumptions about the nature of the object in question. The precise measurement of stellar positions is part of the discipline of astrometry, direct distance measurements are based upon the astronomical unit, which is the distance between the Earth and the Sun. Historically, observations of transits of Venus were crucial in determining the AU, in the first half of the 20th century, observations of asteroids were also important. Keplers laws provide precise ratios of the sizes of the orbits of objects orbiting the Sun, radar is used to measure the distance between the orbits of the Earth and of a second body. From that measurement and the ratio of the two sizes, the size of Earths orbit is calculated. The Earths orbit is known with a precision of a few meters, the most important fundamental distance measurements come from trigonometric parallax. As the Earth orbits the Sun, the position of stars will appear to shift slightly against the more distant background. These shifts are angles in a triangle, with 2 AU making the base leg of the triangle. The amount of shift is small, measuring 1 arcsecond for an object at the 1 parsec distance of the nearest stars. Astronomers usually express distances in units of parsecs, light-years are used in popular media, because parallax becomes smaller for a greater stellar distance, useful distances can be measured only for stars whose parallax is larger than a few times the precision of the measurement. Parallax measurements typically have an accuracy measured in milliarcseconds, the Hubble telescope WFC3 now has the potential to provide a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to 5,000 parsecs for small numbers of stars. By the early 2020s, the GAIA space mission will provide similarly accurate distances to all bright stars. Stars have a velocity relative to the Sun that causes proper motion, for a group of stars with the same spectral class and a similar magnitude range, a mean parallax can be derived from statistical analysis of the proper motions relative to their radial velocities
23.
Metric expansion of space
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The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself changes, metric expansion is a key feature of Big Bang cosmology, is modeled mathematically with the Friedmann-Lemaître-Robertson-Walker metric and is a generic property of the universe we inhabit. However, the model is only on large scales. At smaller scales matter has become bound together under the influence of gravitational attraction, the source of this acceleration is currently unknown. Physicists have postulated the existence of energy, appearing as a cosmological constant in the simplest gravitational models as a way to explain the acceleration. According to the simplest extrapolation of the cosmological model, this acceleration becomes more dominant into the future. The definition of distance used here is the summation or integration of local comoving distances, all done at constant local proper time. For example, galaxies that are more than the Hubble radius, approximately 4.5 gigaparsecs or 14.7 billion light-years, visibility of these objects depends on the exact expansion history of the universe. Because of the rate of expansion, it is also possible for a distance between two objects to be greater than the value calculated by multiplying the speed of light by the age of the universe. These details are a frequent source of confusion among amateurs and even professional physicists, in June 2016, NASA and ESA scientists reported that the universe was found to be expanding 5% to 9% faster than thought earlier, based on studies using the Hubble Space Telescope. To understand the expansion of the universe, it is helpful to discuss briefly what a metric is. A metric defines how a distance can be measured between two points in space, in terms of the coordinate system. Coordinate systems locate points in a space by assigning unique positions on a grid, known as coordinates, the metric is then a formula which describes how displacement through the space of interest can be translated into distances. For example, consider the measurement of distance between two places on the surface of the Earth and this is a simple, familiar example of spherical geometry. Because the surface of the Earth is two-dimensional, points on the surface of the Earth can be specified by two coordinates — for example, the latitude and longitude, specification of a metric requires that one first specify the coordinates used. In our simple example of the surface of the Earth, we could choose any kind of coordinate system we wish, for example latitude and longitude, in general, such shortest-distance paths are called geodesics. In Euclidean geometry, the geodesic is a line, while in non-Euclidean geometry such as on the Earths surface. Indeed, even the great circle path is always longer than the Euclidean straight line path which passes through the interior of the Earth
24.
Eugene Merle Shoemaker
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Eugene Merle Shoemaker, also known as Gene Shoemaker, was an American geologist and one of the founders of the field of planetary science. He is best known for co-discovering the Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy. Shoemaker was born in Los Angeles, California, the son of Muriel May, a teacher, and George Estel Shoemaker, who worked in farming, business, teaching, and motion pictures. For his Ph. D. degree at Princeton, Shoemaker studied the dynamics of Barringer Meteor Crater, located near Winslow. To understand the dynamics, Shoemaker inspected craters that remained after underground atomic bomb tests at the Nevada Test Site at Yucca Flat and he found a ring of ejected material that included shocked quartz, a form of quartz that has a microscopically unique structure caused by intense pressure. Shoemaker helped pioneer the field of astrogeology by founding the Astrogeology Research Program of the United States Geological Survey in 1961 at Flagstaff, Arizona and he was its first director. He was prominently involved in the Lunar Ranger missions to the Moon, Shoemaker was also involved in the training of the American astronauts. Shoemaker would train astronauts during field trips to Meteor Crater and Sunset Crater near Flagstaff and he was a CBS News television commentator on the early Apollo missions, especially the Apollo 8 and Apollo 11 missions, appearing with Walter Cronkite during live coverage of those flights. He was awarded the John Price Wetherill Medal from the Franklin Institute in 1965, coming to Caltech in 1969, he started a systematic search for Earth orbit-crossing asteroids, which resulted in the discovery of several families of such asteroids, including the Apollo asteroids. Shoemaker advanced the idea that sudden geologic changes can arise from asteroid strikes, previously, astroblemes were thought to be remnants of extinct volcanoes — even on the Moon. Shoemaker received the Barringer Medal in 1984 and a National Medal of Science in 1992, in 1993, he co-discovered Comet Shoemaker–Levy 9 using the 18 Schmidt camera at Palomar Observatory. This comet was unique in that it provided the first opportunity for scientists to observe the impact of a comet. Shoemaker–Levy 9 collided with Jupiter in 1994, the resulting impact caused a massive scar on the face of Jupiter. Most scientists at the time were dubious of whether there would even be any evident markings on the planet, Shoemaker spent much of his later years searching for and finding several previously unnoticed or undiscovered impact craters around the world. Shoemaker died on July 18,1997 during one such expedition in a head on car accident while on the Tanami Road northwest of Alice Springs and his vehicle and another were thought to be using the center, relatively smooth part of a heavily rutted, unimproved road. On seeing Shoemaker approaching, the driver of the vehicle pulled hard to his left, and had Shoemaker done the same. But Shoemaker, as an American accustomed to driving on the side of the road, reflexively pulled hard to his right. A head-on collision in which Shoemakers vehicle was traveling at 80 km/h, the occupants of the other vehicle were rendered unconscious, but not seriously injured
25.
Near-Earth object
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A near-Earth object is any small Solar System body whose orbit brings it into proximity with Earth. By definition, a solar system body is a NEO if its closest approach to the Sun is less than 1.3 astronomical unit and it is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. NEOs have become of increased interest since the 1980s because of increased awareness of the potential danger some of the asteroids or comets pose, and mitigations are being researched. In January 2016, NASA announced the Planetary Defense Coordination Office to track NEOs larger than 30 to 50 meters in diameter and coordinate an effective threat response, NEAs have orbits that lie partly between 0.983 and 1.3 AU away from the Sun. When a NEA is detected it is submitted to the IAUs Minor Planet Center for cataloging, some NEAs orbits intersect that of Earths so they pose a collision danger. The United States, European Union, and other nations are currently scanning for NEOs in an effort called Spaceguard. In the United States and since 1998, NASA has a mandate to catalogue all NEOs that are at least 1 kilometer wide. In 2006, it was estimated that 20% of the objects had not yet been found. In 2011, largely as a result of NEOWISE, it was estimated that 93% of the NEAs larger than 1 km had been found, as of 5 February 2017, there have been 875 NEAs larger than 1 km discovered, of which 157 are potentially hazardous. The inventory is much less complete for smaller objects, which still have potential for scale, though not global. Potentially hazardous objects are defined based on parameters that measure the objects potential to make threatening close approaches to the Earth. Mostly objects with an Earth minimum orbit intersection distance of 0.05 AU or less, objects that cannot approach closer to the Earth than 0.05 AU, or are smaller than about 150 m in diameter, are not considered PHOs. This makes them a target for exploration. As of 2016, three near-Earth objects have been visited by spacecraft, more recently, a typical frame of reference for looking at NEOs has been through the scientific concept of risk. In this frame, the risk that any near-Earth object poses is typically seen through a lens that is a function of both the culture and the technology of human society, NEOs have been understood differently throughout history. Each time an NEO is observed, a different risk was posed and it is not just a matter of scientific knowledge. Such perception of risk is thus a product of religious belief, philosophic principles, scientific understanding, technological capabilities, and even economical resourcefulness.03 E −0.4 megatonnes. For instance, it gives the rate for bolides of 10 megatonnes or more as 1 per thousand years, however, the authors give a rather large uncertainty, due in part to uncertainties in determining the energies of the atmospheric impacts that they used in their determination
26.
Aten asteroid
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The Aten asteroids are a group of asteroids, whose orbit brings them into proximity with Earth. The group is named after 2062 Aten, the first of its kind, since then, more than 1,000 Atens have been discovered, of which many are classified as potentially hazardous asteroids. For a list of existing articles, see Aten asteroids and List of Aten asteroids, Aten asteroids are defined by having a semi-major axis of less than one astronomical unit, the average distance from the Earth to the Sun. They also have a greater than 0.983 AU. Asteroids orbits can be highly eccentric, an Aten orbit need not be entirely contained within Earths orbit, as nearly all known Aten asteroids have their aphelion greater than 1 AU although their semi-major axis is less than 1 AU. Observation of objects inferior to the Earths orbit is difficult and this difficulty may be the cause of some sampling bias in the apparent preponderance of eccentric Atens, Aten asteroids account for only about 6% of the known near-Earth asteroid population. Many more Apollo-class asteroids are known than Aten-class asteroids, possibly because of the sampling bias, the shortest semi-major axis for any known Aten asteroid is 2008 EY5 at 0.626 AU. A very small possibility of impact remained for 2036, but this was also eliminated, there are also sixteen known Apohele asteroids, traditionally listed as a subclass of Atens, but generally regarded a separate class of their own. Unlike Atens, Apoheles permanently stay within Earths orbit and do not cross it
27.
Apollo asteroid
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The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth crossing asteroids that have an orbital semi-major axis greater than that of the Earth, as of November 2016, the steadily growing number of known Apollo asteroids has reached a total of 8,180 members. It is by far the largest group of objects, compared to the Aten, Amor. Currently, there are 1,133 numbered Apollos, asteroids are not numbered until they have been observed at two or more oppositions. There are also 1,472 Apollo asteroids that are enough. The closer their semi-major axis is to Earths, the eccentricity is needed for the orbits to cross. The largest known Apollo asteroid is 1866 Sisyphus, with a diameter of about 8.5 km, examples of known Apollo asteroids include, Apollo asteroids Apollo asteroid records List of Apollo minor planets
28.
Amor asteroid
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The Amor asteroids are a group of near-Earth asteroids named after the asteroid 1221 Amor. They approach the orbit of Earth from beyond, but do not cross it, most Amors cross the orbit of Mars. The two moons of Mars, Deimos and Phobos, may be Amor asteroids that were captured by Marss gravity, the most famous member of this group is 433 Eros, which was the first asteroid to be orbited and then landed upon by a human probe. There are three general criteria which an asteroid must meet to be considered a member of the Amor asteroid class, to be considered near, the asteroid must come closer to Earth than to any other major planet. The closest planet to Earth is Venus, which can come as close as 0.27 AU, therefore, an Amor asteroid must come within 0.30 AU of Earths orbit. The asteroids orbit must be outside the orbit of Earth, asteroids that come close to Earth whose orbits are inside Earths orbit are considered Apohele asteroids. The asteroids orbit must not cross Earths orbit, the most commonly used definition of this is that it never orbits closer to the Sun than Earths average distance from the Sun. A more strict definition is that at any point along the asteroids orbit and this takes into consideration the fact that Earths orbit ranges between 0.983 and 1.016 AU from the Sun. It is more difficult to sort out the Amor asteroids from the non-Amor asteroids using this definition, however. These three criteria boil down to a single test for membership, If an asteroid has a perihelion between 1.000 AU and 1.300 AU, it is an Amor asteroid. Any asteroid with this trait is considered an Amor-class asteroid, regardless of its axis, eccentricity, aphelion, inclination, physical properties, orbital stability. An asteroid belongs to the Amor group if, Its orbital period is greater than one year and this is equivalent to saying that its semi-major axis is greater than 1.0 AU. Its orbit does not cross Earths orbit and that is, its lowest point is higher than Earths highest point. It is an object, that is, its perihelion distance q <1.3 AU. In summary, a >1.0 AU and 1.017 AU < q <1.3 AU, there are 6051 Amor asteroids currently known. 960 of them are numbered, and 73 of them are named, Amor asteroids can be partitioned into four subgroups, depending on their average distance from the Sun. The Amor I subgroup consists of Amor asteroids whose semi-major axes are in between Earth and Mars and that is, they have a semi-major axis between 1.000 and 1.523 AU. Less than one fifth of Amor asteroids belong to this subgroup, Amor I asteroids have lower eccentricities than the other subgroups of Amors
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Trojan (astronomy)
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In astronomy, a trojan is a minor planet or moon that shares the orbit of a planet or larger moon, wherein the trojan remains in the same, stable position relative to the larger object. In particular, a trojan remains near one of the two points of stability – designated L4 and L5 – which lie approximately 60° ahead of and behind the larger body. Trojan points make up two of five types of Lagrangian points, and a trojan is a type of Lagrangian object and they are one type of co-orbital object. In this arrangement, the star and the smaller planet orbit about their common barycenter. A much smaller mass located at one of the Lagrangian points is subject to a gravitational force that acts through this barycenter. Hence the object can orbit around the barycenter with the orbital period as the planet. The Jupiter trojans account for most known trojans in the Solar System and they are divided into the Greek camp in front of and the Trojan camp trailing behind Jupiter in their orbit. Numerical calculations of the dynamics involved indicate that Saturn and Uranus probably do not have any primordial trojans. The discovery of the first Earth trojan,2010 TK7, was announced by NASA in 2011, unlike trojan minor planets that share the orbit with a planet, a trojan moon is a moon orbiting near the trojan point of another, larger moon. All known trojan moons are part of the Saturn system, telesto and Calypso are trojans of Tethys, and Helene and Polydeuces of Dione. There is also a concept of a trojan planet, a planet that orbits at the trojan point of another, larger planet. Such a pair of co-orbital exoplanets was already thought to exist in another star system, in 1772, the Italian–French mathematician and astronomer Joseph-Louis Lagrange obtained two constant-pattern solutions of the general three-body problem. In the restricted problem, with one mass negligible, the five possible positions of that mass are now termed Lagrangian points. The term trojan originally referred to the asteroids that orbit close to the Lagrangian points of Jupiter. These have long been named after characters from the Trojan War of Greek mythology, there are two exceptions, which were named before the convention was put in place, the Greek-themed 617 Patroclus and the Trojan-themed 624 Hektor, which were assigned to the wrong sides. Astronomers estimate that the Jupiter trojans are about as numerous as the asteroids of the asteroid belt, later on, objects were found orbiting near the Lagrangian points of Neptune, Mars, Earth, Uranus, and Venus. Minor planets at the Lagrangian points of other than Jupiter may be called Lagrangian minor planets. 17 Neptune trojans are known, but large Neptune trojans are expected to outnumber the large Jupiter trojans by an order of magnitude,2010 TK7 was confirmed to be the first known Earth trojan in 2011
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Natural satellite
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A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet. In the Solar System there are six planetary satellite systems containing 178 known natural satellites, four IAU-listed dwarf planets are also known to have natural satellites, Pluto, Haumea, Makemake, and Eris. As of January 2012, over 200 minor-planet moons have been discovered, the Earth–Moon system is unique in that the ratio of the mass of the Moon to the mass of Earth is much greater than that of any other natural-satellite–planet ratio in the Solar System. At 3,474 km across, Earths Moon is 0.27 times the diameter of Earth, the first known natural satellite was the Moon, but it was considered a planet until Copernicus introduction of heliocentrism in 1543. Until the discovery of the Galilean satellites in 1610, however, galileo chose to refer to his discoveries as Planetæ, but later discoverers chose other terms to distinguish them from the objects they orbited. The first to use of the satellite to describe orbiting bodies was the German astronomer Johannes Kepler in his pamphlet Narratio de Observatis a se quatuor Iouis satellitibus erronibus in 1610. He derived the term from the Latin word satelles, meaning guard, attendant, or companion, the term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of moon. In 1957, however, the launching of the artificial object Sputnik created a need for new terminology, to further avoid ambiguity, the convention is to capitalize the word Moon when referring to Earths natural satellite, but not when referring to other natural satellites. A few recent authors define moon as a satellite of a planet or minor planet, there is no established lower limit on what is considered a moon. Small asteroid moons, such as Dactyl, have also been called moonlets, the upper limit is also vague. Two orbiting bodies are described as a double body rather than primary. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition of what constitutes a moon, some authors consider the Pluto–Charon system to be a double planet. In contrast, irregular satellites are thought to be captured asteroids possibly further fragmented by collisions, most of the major natural satellites of the Solar System have regular orbits, while most of the small natural satellites have irregular orbits. The Moon and possibly Charon are exceptions among large bodies in that they are thought to have originated by the collision of two large proto-planetary objects. The material that would have placed in orbit around the central body is predicted to have reaccreted to form one or more orbiting natural satellites. As opposed to planetary-sized bodies, asteroid moons are thought to form by this process. Triton is another exception, although large and in a close, circular orbit, its motion is retrograde, most regular moons in the Solar System are tidally locked to their respective primaries, meaning that the same side of the natural satellite always faces its planet. The only known exception is Saturns natural satellite Hyperion, which rotates chaotically because of the influence of Titan
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Leda (moon)
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Leda, also known as Jupiter XIII, is a prograde irregular satellite of Jupiter. It was discovered by Charles T. Kowal at the Mount Palomar Observatory on September 14,1974 and it was named after Leda, who was a lover of Zeus, the Greek equivalent of Jupiter. Kowal suggested the name and the IAU endorsed it in 1975, Leda belongs to the Himalia group, five moons orbiting between 11 and 13 Gm from Jupiter at an inclination of about 27. 5°. The orbital elements given here are as of January 2000, but they are changing due to solar. The 1956 British film Fire Maidens from Outer Space was set on Jupiters 13th moon, in Brenda Hiatts 2013 teen, science fiction themed romance novel, Starstruck, Rigel impresses Marsha with a telescope that clearly sees Leda. Rigel is in turn impressed that Marsha knows so much about the obscure Moon of Jupiter, in Liu Cixins 2010 science fiction novel Deaths End, Jupiter XIII is consumed by a man-made blackhole, thus creating the first-ever stable man-made blackhole. Jupiters moons in fiction Leda Overview by NASAs Solar System Exploration David Jewitt pages Jupiters Known Satellites
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Themisto (moon)
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Themisto, also known as Jupiter XVIII, is a small prograde irregular satellite of Jupiter. It was discovered in 1975, subsequently lost, and rediscovered in 2000, Themisto was first discovered by Charles T. Kowal and Elizabeth Roemer on September 30,1975, reported on October 3,1975, and designated S/1975 J1. However, not enough observations were made to establish an orbit and it was subsequently lost, Themisto appeared as a footnote in astronomy textbooks into the 1980s. Then, in 2000, a new satellite was discovered by Scott S. Sheppard. Jewitt, Yanga R. Fernández and Eugene A. Magnier and it was soon confirmed that this was the same as the one observed in 1975. In October 2002 it was named after Themisto, daughter of the river god Inachus. Themistos orbit is unusual, unlike most of Jupiters moons, which orbit in distinct groups, the moon is located midway between the Galilean moons and the first group of prograde irregular moons, called the Himalia group. Themisto is about 8 kilometers in diameter and that figure can be used to find a surface area of between 200 and 380 square kilometers. International Astronomical Union Minor Planet Center, David Jewitts pages Jupiters Known Satellites
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Ecliptic
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The ecliptic is the apparent path of the Sun on the celestial sphere, and is the basis for the ecliptic coordinate system. It also refers to the plane of this path, which is coplanar with the orbit of Earth around the Sun, the motions as described above are simplifications. Due to the movement of Earth around the Earth–Moon center of mass, due to further perturbations by the other planets of the Solar System, the Earth–Moon barycenter wobbles slightly around a mean position in a complex fashion. The ecliptic is actually the apparent path of the Sun throughout the course of a year, because Earth takes one year to orbit the Sun, the apparent position of the Sun also takes the same length of time to make a complete circuit of the ecliptic. With slightly more than 365 days in one year, the Sun moves a little less than 1° eastward every day, again, this is a simplification, based on a hypothetical Earth that orbits at uniform speed around the Sun. The actual speed with which Earth orbits the Sun varies slightly during the year, for example, the Sun is north of the celestial equator for about 185 days of each year, and south of it for about 180 days. The variation of orbital speed accounts for part of the equation of time, if the equator is projected outward to the celestial sphere, forming the celestial equator, it crosses the ecliptic at two points known as the equinoxes. The Sun, in its apparent motion along the ecliptic, crosses the equator at these points, one from south to north. The crossing from south to north is known as the equinox, also known as the first point of Aries. The crossing from north to south is the equinox or descending node. Likewise, the ecliptic itself is not fixed, the gravitational perturbations of the other bodies of the Solar System cause a much smaller motion of the plane of Earths orbit, and hence of the ecliptic, known as planetary precession. The combined action of two motions is called general precession, and changes the position of the equinoxes by about 50 arc seconds per year. Once again, this is a simplification, periodic motions of the Moon and apparent periodic motions of the Sun cause short-term small-amplitude periodic oscillations of Earths axis, and hence the celestial equator, known as nutation. Obliquity of the ecliptic is the used by astronomers for the inclination of Earths equator with respect to the ecliptic. It is about 23. 4° and is currently decreasing 0.013 degrees per hundred years due to planetary perturbations, the angular value of the obliquity is found by observation of the motions of Earth and other planets over many years. From 1984, the Jet Propulsion Laboratorys DE series of computer-generated ephemerides took over as the ephemeris of the Astronomical Almanac. Obliquity based on DE200, which analyzed observations from 1911 to 1979, was calculated, jPLs fundamental ephemerides have been continually updated. J. Laskar computed an expression to order T10 good to 0″. 04/1000 years over 10,000 years, all of these expressions are for the mean obliquity, that is, without the nutation of the equator included
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2060 Chiron
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2060 Chiron, also known as 95P/Chiron, is a minor planet in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles T. Kowal, it was the member of a new class of objects now known as centaurs—bodies orbiting between the asteroid belt and the Kuiper belt. Besides the four giant planets, Chiron and 10199 Chariklo, also a centaur, are the other bodies in the Solar System known to have rings. Although it was called an asteroid and classified only as a minor planet with the designation 2060 Chiron. Today it is classified as both a planet and a comet, and is accordingly also known by the cometary designation 95P/Chiron. Chiron is named after the centaur Chiron in Greek mythology, michael Brown lists it as possibly a dwarf planet with a measured diameter of 206 km which is near the lower limit for an icy dwarf planet. Chiron was discovered on 1 November 1977 by Charles Kowal from images taken on 18 October at Palomar Observatory and it was given the temporary designation of 1977 UB. It was found near aphelion and at the time of discovery it was the most distant known minor planet, Chiron was even claimed as the tenth planet by the press. Chiron was later found on several images, going back to 1895. It had been at perihelion in 1945 but was not discovered then because there were few searches being made at time. The Lowell Observatorys survey for distant planets would not have gone down faint enough in the 1930s and it was named Chiron in 1979 after Chiron, one of the centaurs, it was suggested that the names of other centaurs be reserved for objects of the same type. Chirons orbit was found to be eccentric, with perihelion just inside the orbit of Saturn. According to the program Solex, Chirons closest approach to Saturn in modern times was around May 720, during this passage Saturns gravity caused Chirons semi-major axis to decrease from 14. 55±0.12 AU to 13.7 AU. It does not come nearly as close to Uranus, Chiron crosses Uranuss orbit where the latter is farther than average from the Sun, Chiron attracted considerable interest because it was the first object discovered in such an orbit, well outside the asteroid belt. Chiron is classified as a centaur, the first of a class of objects orbiting between the outer planets, Chiron is a Saturn–Uranus object because its perihelion lies in Saturns zone of control and its aphelion lies in that of Uranus. Chiron is probably a refugee from the Kuiper belt and will become a short-period comet in about a million years. Chiron came to perihelion in 1996, the visible and near-infrared spectrum of Chiron is neutral, and is similar to that of C-type asteroids and the nucleus of Halleys Comet. The near-infrared spectrum of Chiron shows absence of water ice, the assumed size of an object depends on its absolute magnitude and the albedo
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Neptune
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Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the planet. Neptune is 17 times the mass of Earth and is more massive than its near-twin Uranus. Neptune orbits the Sun once every 164.8 years at a distance of 30.1 astronomical units. It is named after the Roman god of the sea and has the astronomical symbol ♆, Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to perturbation by an unknown planet. Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the predicted by Urbain Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the remaining known 14 moons were located telescopically until the 20th century. The planets distance from Earth gives it a small apparent size. Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989, the advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar. Neptunes composition can be compared and contrasted with the Solar Systems other giant planets, however, its interior, like that of Uranus, is primarily composed of ices and rock, which is why Uranus and Neptune are normally considered ice giants to emphasise this distinction. Traces of methane in the outermost regions in part account for the blue appearance. In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptunes atmosphere has active, for example, at the time of the Voyager 2 flyby in 1989, the planets southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, because of its great distance from the Sun, Neptunes outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching 55 K. Temperatures at the centre are approximately 5,400 K. Neptune has a faint and fragmented ring system. On both occasions, Galileo seems to have mistaken Neptune for a star when it appeared close—in conjunction—to Jupiter in the night sky, hence. At his first observation in December 1612, Neptune was almost stationary in the sky because it had just turned retrograde that day and this apparent backward motion is created when Earths orbit takes it past an outer planet. Because Neptune was only beginning its yearly cycle, the motion of the planet was far too slight to be detected with Galileos small telescope
