The newton is the International System of Units derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics Newton's second law of motion. See below for the conversion factors. One newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force. In 1946, Conférence Générale des Poids et Mesures Resolution 2 standardized the unit of force in the MKS system of units to be the amount needed to accelerate 1 kilogram of mass at the rate of 1 metre per second squared. In 1948, the 9th CGPM Resolution 7 adopted the name newton for this force; the MKS system became the blueprint for today's SI system of units. The newton thus became the standard unit of force in the Système international d'unités, or International System of Units; this SI unit is named after Isaac Newton. As with every International System of Units unit named for a person, the first letter of its symbol is upper case.
However, when an SI unit is spelled out in English, it is treated as a common noun and should always begin with a lower case letter —except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case. Newton's second law of motion states that F = ma, where F is the force applied, m is the mass of the object receiving the force, a is the acceleration of the object; the newton is therefore: where the following symbols are used for the units: N for newton, kg for kilogram, m for metre, s for second. In dimensional analysis: F = M L T 2 where F is force, M is mass, L is length and T is time. At average gravity on Earth, a kilogram mass exerts a force of about 9.8 newtons. An average-sized apple exerts about one newton of force. 1 N = 0.10197 kg × 9.80665 m/s2 The weight of an average adult exerts a force of about 608 N. 608 N = 62 kg × 9.80665 m/s2 It is common to see forces expressed in kilonewtons where 1 kN = 1000 N.
For example, the tractive effort of a Class Y steam train locomotive and the thrust of an F100 fighter jet engine are both around 130 kN. One kilonewton, 1 kN, is about 100 kg of load. 1 kN = 102 kg × 9.81 m/s2 So for example, a platform that shows it is rated at 321 kilonewtons, will safely support a 32,100 kilograms load. Specifications in kilonewtons are common in safety specifications for: the holding values of fasteners, Earth anchors, other items used in the building industry. Working loads in tension and in shear. Rock climbing equipment. Thrust of rocket engines and launch vehicles clamping forces of the various moulds in injection moulding machines used to manufacture plastic parts
The Milky Way is the galaxy that contains our Solar System. The name describes the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye; the term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος. From Earth, the Milky Way appears as a band. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610; until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies; the Milky Way is a barred spiral galaxy with a diameter between 200,000 light-years. It is estimated to contain 100 -- more than 100 billion planets; the Solar System is located at a radius of 26,490 light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust.
The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The galactic center is an intense radio source known as Sagittarius A*, assumed to be a supermassive black hole of 4.100 million solar masses. Stars and gases at a wide range of distances from the Galactic Center orbit at 220 kilometers per second; the constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much of the mass of the Milky Way is invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This conjectural mass has been termed "dark matter"; the rotational period is about 240 million years at the radius of the Sun. The Milky Way as a whole is moving at a velocity of 600 km per second with respect to extragalactic frames of reference; the oldest stars in the Milky Way are nearly as old as the Universe itself and thus formed shortly after the Dark Ages of the Big Bang. The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster, itself a component of the Laniakea Supercluster.
The Milky Way is visible from Earth as a hazy band of white light, some 30° wide, arching across the night sky. In night sky observing, although all the individual naked-eye stars in the entire sky are part of the Milky Way, the term “Milky Way” is limited to this band of light; the light originates from the accumulation of unresolved stars and other material located in the direction of the galactic plane. Dark regions within the band, such as the Great Rift and the Coalsack, are areas where interstellar dust blocks light from distant stars; the area of sky that the Milky Way obscures is called the Zone of Avoidance. The Milky Way has a low surface brightness, its visibility can be reduced by background light, such as light pollution or moonlight. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be visible. It should be visible if the limiting magnitude is +5.1 or better and shows a great deal of detail at +6.1. This makes the Milky Way difficult to see from brightly lit urban or suburban areas, but prominent when viewed from rural areas when the Moon is below the horizon.
Maps of artificial night sky brightness show that more than one-third of Earth's population cannot see the Milky Way from their homes due to light pollution. As viewed from Earth, the visible region of the Milky Way's galactic plane occupies an area of the sky that includes 30 constellations; the Galactic Center lies in the direction of Sagittarius. From Sagittarius, the hazy band of white light appears to pass around to the galactic anticenter in Auriga; the band continues the rest of the way around the sky, back to Sagittarius, dividing the sky into two equal hemispheres. The galactic plane is inclined by about 60° to the ecliptic. Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic, relative to the galactic plane; the north galactic pole is situated at right ascension 12h 49m, declination +27.4° near β Comae Berenices, the south galactic pole is near α Sculptoris.
Because of this high inclination, depending on the time of night and year, the arch of the Milky Way may appear low or high in the sky. For observers from latitudes 65° north to 65° south, the Milky Way passes directly overhead twice a day; the Milky Way is the second-largest galaxy in the Local Group, with its stellar disk 100,000 ly in diameter and, on average 1,000 ly thick. The Milky Way is 1.5 trillion times the mass of the Sun. To compare the relative physical scale of the Milky Way, if the Solar System out to Neptune were the size of a US quarter, the Milky Way would be the size of the contiguous United States. There is a ring-like filament of stars rippling above and below the flat galactic plane, wrapping around the Milky Way at a diameter of 150,000–180,000 light-years, which may be part of the Milky Way itself. Estimates of the mass of the Milky Way vary, depending upon the method and data used; the low end of the estimate range is 5.8×1011 solar masses, somewhat less than that of the Andromeda Galaxy.
Measurements using the Very Long Baseline Array in 2009 found
New Horizons is an interplanetary space probe, launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory and the Southwest Research Institute, with a team led by S. Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, a secondary mission to fly by and study one or more other Kuiper belt objects in the decade to follow, which as of 2019 includes 2014 MU69, it is the fifth space probe to achieve the escape velocity needed to leave the Solar System. On January 19, 2006, New Horizons was launched from Cape Canaveral Air Force Station by an Atlas V rocket directly into an Earth-and-solar escape trajectory with a speed of about 16.26 km/s. It was the fastest man-made object launched from Earth. After a brief encounter with asteroid 132524 APL, New Horizons proceeded to Jupiter, making its closest approach on February 28, 2007, at a distance of 2.3 million kilometers.
The Jupiter flyby provided a gravity assist. Most of the post-Jupiter voyage was spent in hibernation mode to preserve on-board systems, except for brief annual checkouts. On December 6, 2014, New Horizons was brought back online for the Pluto encounter, instrument check-out began. On January 15, 2015, the spacecraft began its approach phase to Pluto. On July 14, 2015, at 11:49 UTC, it flew 12,500 km above the surface of Pluto, making it the first spacecraft to explore the dwarf planet. On October 25, 2016, at 21:48 UTC, the last of the recorded data from the Pluto flyby was received from New Horizons. Having completed its flyby of Pluto, New Horizons maneuvered for a flyby of Kuiper belt object 2014 MU69 "Ultima Thule", which occurred on January 1, 2019, when it was 43.4 AU from the Sun. In August 2018, NASA cited results by Alice on New Horizons to confirm the existence of a "hydrogen wall" at the outer edges of the Solar System; this "wall" was first detected in 1992 by the two Voyager spacecraft.
In August 1992, JPL scientist Robert Staehle called Pluto discoverer Clyde Tombaugh, requesting permission to visit his planet. "I told him he was welcome to it," Tombaugh remembered, "though he's got to go one long, cold trip." The call led to a series of proposed Pluto missions, leading up to New Horizons. Stamatios "Tom" Krimigis, head of the Applied Physics Laboratory's space division, one of many entrants in the New Frontiers Program competition, formed the New Horizons team with Alan Stern in December 2000. Appointed as the project's principal investigator, Stern was described by Krimigis as "the personification of the Pluto mission". New Horizons was based on Stern's work since Pluto 350 and involved most of the team from Pluto Kuiper Express; the New Horizons proposal was one of five that were submitted to NASA. It was selected as one of two finalists to be subject to a three-month concept study, in June 2001; the other finalist, POSSE, was a separate, but similar Pluto mission concept by the University of Colorado Boulder, led by principal investigator Larry W. Esposito, supported by the JPL, Lockheed Martin and the University of California.
However, the APL, in addition to being supported by Pluto Kuiper Express developers at the Goddard Space Flight Center and Stanford University, were at an advantage. In November 2001, New Horizons was selected for funding as part of the New Frontiers program. However, the new NASA Administrator appointed by the Bush Administration, Sean O'Keefe, was not supportive of New Horizons, cancelled it by not including it in NASA's budget for 2003. NASA's Associate Administrator for the Science Mission Directorate Ed Weiler prompted Stern to lobby for the funding of New Horizons in hopes of the mission appearing in the Planetary Science Decadal Survey. After an intense campaign to gain support for New Horizons, the Planetary Science Decadal Survey of 2003–2013 was published in the summer of 2002. New Horizons topped the list of projects considered the highest priority among the scientific community in the medium-size category. Weiler stated that it was a result that " administration was not going to fight".
Funding for the mission was secured following the publication of the report, Stern's team were able to start building the spacecraft and its instruments, with a planned launch in January 2006 and arrival at Pluto in 2015. Alice Bowman became Mission Operations Manager. New Horizons is the first mission in NASA's New Frontiers mission category and more expensive than the Discovery missions but smaller than the Flagship Program; the cost of the mission is $700 million over 15 years. The spacecraft was built by Southwest Research Institute and the Johns Hopkins Applied Physics Laboratory; the mission's principal investigator is Alan Stern of the Southwest Research Institute. After separation from the launch vehicle, ov
New Frontiers program
The New Frontiers program is a series of space exploration missions being conducted by NASA with the purpose of researching several of the Solar System bodies, including the dwarf planet Pluto. NASA is encouraging both domestic and international scientists to submit mission proposals for the program. New Frontiers was built on the innovative approach used by the Discovery and Explorer Programs of principal investigator-led missions, it is designed for medium-class missions that cannot be accomplished within the cost and time constraints of Discovery, but are not as large as Large Strategic Science Missions. There are three New Frontiers missions in progress: New Horizons, launched in 2006 and reached Pluto in 2015, launched in 2011 and entered Jupiter orbit in 2016, OSIRIS-REx, launched in September 2016 towards asteroid Bennu for detailed studies from 2018 to 2021 and a sample return to Earth in 2023; the New Frontiers program was developed and advocated by NASA and granted by Congress in CY 2002 and 2003.
This effort was led by two long-time NASA executives at Headquarters at that time: Edward Weiler, Associate Administrator of Science, Colleen Hartman, Solar System Exploration Division Director. The mission to Pluto had been selected before this program was endorsed and funded, so the mission to Pluto, called New Horizons, was "grandfathered" into the New Frontiers program; the 2003 Planetary Science Decadal Survey from the National Academy of Sciences identified destinations that served as the source of the first competition for the New Frontiers program. The program name was selected by Hartman based on President John F. Kennedy's speech in 1960, in which he said "We stand, today, on the edge of a New Frontier." Examples of proposed mission concepts include two broad groups based on Planetary Science Decadal Survey goals. From New Frontiers in the Solar System: An Integrated Exploration Strategy Kuiper Belt Pluto Explorer Jupiter Polar Orbiter with Probes Venus In Situ Explorer Lunar South Pole-Aitken Basin Sample Return Mission Comet Surface Sample Return Mission: Comet Astrobiology Exploration Sample Return From Vision and Voyages for Planetary Science in the Decade 2013–2022 Io Volcano Observer Lunar Geophysical Network Saturn Atmospheric Entry Probe Trojan Tour and Rendezvous New Horizons, a mission to Pluto, was launched on January 19, 2006.
After a Jupiter gravity assist in February 2007 the spacecraft continued towards Pluto. The primary mission flyby occurred in July 2015 and the spacecraft was targeted toward one Kuiper Belt object called 2014 MU69 for a January 1, 2019 flyby. Another mission, considered with this mission was New Horizons 2. Juno is a Jupiter exploration mission which launched on August 5, 2011 and arrived in July 2016, it is the first solar-powered spacecraft to explore an outer planet. The craft was placed into a polar orbit in order to study the planet's magnetic field and internal structure. NASA's Galileo mission to Jupiter provided extensive knowledge about its upper atmosphere, further study of Jupiter is crucial not only to the understanding of its origin and nature of the Solar System, but of giant extrasolar planets in general; the Juno spacecraft investigation is intended to address the following objectives for Jupiter: Understand Jupiter's gross dynamical and structural properties through determination of the mass and size of Jupiter's core, its gravitational and magnetic fields, internal convection.
OSIRIS-REx stands for "Origins, Spectral Interpretation, Resource Identification, Regolith Explorer", was launched on 8 September 2016. This mission plan is to orbit an asteroid, at the time named 1999 RQ36, by 2020. After extensive measurements, the spacecraft will collect a sample from the asteroid's surface for return to Earth in 2023; the mission, excluding the launch vehicle, is expected to cost $800 million. The returned sample will help scientists answer long-held questions about the formation of the Solar System and the origin of complex organic molecules necessary for the origin of life. Asteroid Bennu is a potential future Earth impactor and is listed on the Sentry Risk Table with the third highest rating on the Palermo Technical Impact Hazard Scale. In the late 2100s there is a cumulative chance of about 0.07% it could strike Earth, therefore there is a need to measure the composition and Yarkovsky effect of the asteroid. Competition for the fourth mission began in January 2017. NASA selected two proposals for additional concept studies on December 20, 2017, will select a winner in the competition in 2019, launch it by 2024.
Investigators may propose the use of Multi-Mission Radioisotope Thermoelectric Generators, the NASA Evolutionary Xenon Thruster ion propulsion system. The development cost cap is $1 billion. Per recommendation by the Decadal Survey, NASA's announcement of opportunity was limited to six mission themes: Comet Surface Sample Return - a comet nucleus lander and sample return mission Lunar South Pole Sample Return - a mission to land at the Moon's South Pole–Aitken basin and return samples to Earth Ocean Worlds Saturn Probe - an atmospheric prob
In optics, an aperture is a hole or an opening through which light travels. More the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An optical system has many openings or structures that limit the ray bundles; these structures may be the edge of a lens or mirror, or a ring or other fixture that holds an optical element in place, or may be a special element such as a diaphragm placed in the optical path to limit the light admitted by the system. In general, these structures are called stops, the aperture stop is the stop that determines the ray cone angle and brightness at the image point. In some contexts in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the physical stop or the opening itself. For example, in a telescope, the aperture stop is the edges of the objective lens or mirror. One speaks of a telescope as having, for example, a 100-centimeter aperture. Note that the aperture stop is not the smallest stop in the system.
Magnification and demagnification by lenses and other elements can cause a large stop to be the aperture stop for the system. In astrophotography, the aperture may be given as a linear measure or as the dimensionless ratio between that measure and the focal length. In other photography, it is given as a ratio. Sometimes stops and diaphragms are called apertures when they are not the aperture stop of the system; the word aperture is used in other contexts to indicate a system which blocks off light outside a certain region. In astronomy, for example, a photometric aperture around a star corresponds to a circular window around the image of a star within which the light intensity is assumed; the aperture stop is an important element in most optical designs. Its most obvious feature is; this can be either unavoidable, as in a telescope where one wants to collect as much light as possible. In both cases, the size of the aperture stop is constrained by things other than the amount of light admitted. Smaller stops produce a longer depth of field, allowing objects at a wide range of distances to all be in focus at the same time.
The stop limits the effect of optical aberrations. If the stop is too large, the image will be distorted. More sophisticated optical system designs can mitigate the effect of aberrations, allowing a larger stop and therefore greater light collecting ability; the stop determines. Larger stops can cause the intensity reaching the film or detector to fall off toward the edges of the picture when, for off-axis points, a different stop becomes the aperture stop by virtue of cutting off more light than did the stop, the aperture stop on the optic axis. A larger aperture stop requires larger diameter optics, which are more expensive. In addition to an aperture stop, a photographic lens may have one or more field stops, which limit the system's field of view; when the field of view is limited by a field stop in the lens vignetting results. The biological pupil of the eye is its aperture in optics nomenclature. Refraction in the cornea causes the effective aperture to differ from the physical pupil diameter.
The entrance pupil is about 4 mm in diameter, although it can range from 2 mm in a brightly lit place to 8 mm in the dark. In astronomy, the diameter of the aperture stop is a critical parameter in the design of a telescope. One would want the aperture to be as large as possible, to collect the maximum amount of light from the distant objects being imaged; the size of the aperture is limited, however, in practice by considerations of cost and weight, as well as prevention of aberrations. Apertures are used in laser energy control, close aperture z-scan technique, diffractions/patterns, beam cleaning. Laser applications include Q-switching, high intensity x-ray control. In light microscopy, the word aperture may be used with reference to either the condenser, field iris or objective lens. See Optical microscope; the aperture stop of a photographic lens can be adjusted to control the amount of light reaching the film or image sensor. In combination with variation of shutter speed, the aperture size will regulate the film's or image sensor's degree of exposure to light.
A fast shutter will require a larger aperture to ensure sufficient light exposure, a slow shutter will require a smaller aperture to avoid excessive exposure. A device called a diaphragm serves as the aperture stop, controls the aperture; the diaphragm functions much like the iris of the eye – it controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus. In general, the smaller the aperture, the greater the distance from the plane of focus the subject matter may be while
Nuclear power in space
Nuclear power in space is the use of nuclear power in outer space either small fission systems or radioactive decay for electricity or heat. Another use is for scientific observation, as in a Mössbauer spectrometer. One common type is a radioisotope thermoelectric generator, used on many space probes and on manned lunar missions, another is small fission reactors for Earth observation satellites such as the TOPAZ nuclear reactor. A radioisotope heater unit provides heat from radioactive decay of a material and can produce heat for decades. Russia has sent about 40 reactors into space and its TOPAZ-II reactor can produce 10 kilowatts; the Romashka reactor family uses uranium and direct thermoelectric conversion to electricity, rather than using a heated fluid to drive a turbine. The United States tested a nuclear reactor in space for 43 days in 1965. While not yet tested in space, the test of the Demonstration Using Flattop Fission on September 13, 2012 was the first test of a nuclear reactor power system for space since then.
Examples of nuclear power for space propulsion systems include nuclear electric rocket, radioisotope rocket, radioisotope electric propulsion. One of the more explored is the nuclear thermal rocket, tested in the NERVA program. See Category:Nuclear spacecraft propulsion. Nuclear pulse propulsion was the subject of Project Orion While solar power is much more used, nuclear power offers great advantages in many areas. Solar cells, although efficient, can only supply energy to spacecraft in orbits where the solar flux is sufficiently high, such as low Earth orbit and interplanetary destinations close enough to the Sun. Unlike solar cells, nuclear power systems function independently of sunlight, necessary for deep space exploration. Nuclear reactors are beneficial in space because of their lower weight-to-capacity ratio than solar cells. Therefore, nuclear power systems take up much less space than solar power systems. Compact spacecraft are easier to direct in space when precision is needed. Estimates of nuclear power, which can power both life support and propulsion systems, suggest that use of these systems can reduce both cost and flight time.
Selected applications and/or technologies for space include Radioisotope thermoelectric generator Radioisotope heater unit Radioisotope piezoelectric generator Radioisotope rocket Nuclear thermal rocket Nuclear pulse propulsion Nuclear electric rocket For more than fifty years, radioisotope thermoelectric generators have been the United States’ main nuclear power source in space. RTGs offer many benefits. RTGs are desirable for use in parts of space where solar power is not a viable power source. Dozens of RTGs have been implemented to power 25 different US spacecraft, some of which have been operating for more than 20 years. Over 40 radioisotope thermoelectric generators have been used globally on space missions; the advanced Stirling radioisotope generator produces four times the electric power of an RTG per unit of nuclear fuel, but it is not yet ready to be implemented on an actual mission. NASA plans to utilize two ASRGs to explore Titan in the distant future. Radioisotope power generators include: SNAP-19, SNAP-27 MHW-RTG GPHS-RTG MMRTG ASRG Radioisotope heater units are used on spacecraft to warm scientific instruments to the proper temperature so they operate efficiently.
A larger model of RHU called the General Purpose Heat Source is used to power RTGs and the ASRG. Slow-decaying radioisotopes have been proposed for use on realistic interstellar probes with multi-decade lifetimes. Another direction for development is an RTG assisted by subcritical reactions. Fission power systems may be utilized to propulsion systems. In terms of heating requirements, when spacecraft require more than 100 kW for power, fission systems are much more cost effective than RTGs. Over the past few decades, several fission reactors have been proposed, but these fission systems haven’t been utilized in US space projects as prominently as radioisotope systems have; the Soviet Union, launched 31 BES-5 low power fission reactors in their RORSAT satellites utilizing thermoelectric converters between 1967 and 1988. Shortly after, the Soviet Union developed TOPAZ reactors, which utilize thermionic converters instead. In 2008, NASA announced plans to utilize a small fission power system to be used on the surface of the moon and Mars, began testing "key" technologies for it to come to fruition.
Nuclear thermal propulsion systems are based on the heating power of a fission reactor, offering a more efficient propulsion system for thrust in launches and landings than one powered by chemical reactions. Current research focuses more on nuclear electric systems as the power source for providing thrust to propel spacecraft that are in space. Other space fission reactors for powering space vehicles include the SAFE-400 reactor and the HOMER-15. In 2020, Roscosmos plans to launch a spacecraft utilizing nuclear-powered propulsion systems, which includes a small gas-cooled fission reactor with 1 MWe; as of 2010, more than 30 small fission power system nuclear reactors have been sent into space in the Soviet RORSAT satellites, with only one—SNAP-10A—by the US. Proposed fission power system spacecraft and explorati
An interstellar probe is a space probe that has left—or is expected to leave—the Solar System and enter interstellar space, defined as the region beyond the heliopause. It refers to probes capable of reaching other star systems. There are five interstellar probes: Voyager 2, Pioneer 10, Pioneer 11 and New Horizons; as of 2019, Voyager 1 and Voyager 2 are only probes to have reached interstellar space. The other three are on interstellar trajectories; the termination shock is the point in the heliosphere where the solar wind slows down to subsonic speed. Though the termination shock happens as close as 80–100 AU, the maximum extent of the region in which the Sun's gravitational field is dominant is thought to be at around 230,000 astronomical units; this point is close to Alpha Centauri, located 4.36 light years away. Although the probes will be under the influence of the Sun for a long time, their velocities far exceed the Sun's escape velocity, so they will leave forever. Interstellar space is defined as that which lies beyond a magnetic region that extends about 122 AU from the sun, as detected by Voyager 1, the equivalent region of influence surrounding other stars.
Voyager 1 entered interstellar space in 2012. Interstellar Probe is the name of a proposed NASA space probe intended to travel out 200 AU in 15 years, studied in 1999. In April 2016, scientists announced Breakthrough Starshot, a Breakthrough Initiatives program, to develop a proof-of-concept fleet of small centimeter-sized light sail spacecraft, named StarChip, capable of making the journey to Alpha Centauri, the nearest extrasolar star system, at speeds of 20% and 15% of the speed of light, taking between 20 and 30 years to reach the star system and about 4 years to notify Earth of a successful arrival. Planetary scientist G. Laughlin noted that with current technology a probe sent to Alpha Centauri would take 40,000 years to arrive, but expressed hope for new technology to be developed to make the trip within a human lifetime. On that timescale the stars move notably; as an example, in 40,000 years Ross 248 will be closer to Earth than Alpha Centauri. One technology, proposed to achieve higher speeds is an E-sail.
By harnessing solar wind, it might be possible to achieve 20-30 AU per year without using propellant. Voyager 1 is a space probe launched by NASA on September 5, 1977. At a distance of about 139.114 AU as of 31 March 2019, it is the farthest manmade object from Earth. It was estimated that Voyager 1 crossed the termination shock on December 15, 2004 at a distance of 94 AU from the Sun. At the end of 2011, Voyager 1 entered and discovered a stagnation region where charged particles streaming from the Sun slow and turn inward, the Solar System's magnetic field is doubled in strength as interstellar space appears to be applying pressure. Energetic particles originating in the Solar System declined by nearly half, while the detection of high-energy electrons from outside increases 100-fold; the inner edge of the stagnation region is located 113 astronomical units from the Sun. In 2013 it was thought Voyager 1 crossed the heliopause and entered interstellar space on August 25, 2012 at distance of 121 AU from the Sun, making it the first known human-manufactured object to do so.
As of 2017, the probe was moving with a relative velocity to the Sun of about 16.95 km/s. If it does not hit anything, Voyager 1 could reach the Oort cloud in about 300 years Voyager 2 crossed the heliopause and entered interstellar space on November 5, 2018, it had passed the termination shock into the heliosheath on October 30, 2007. As of 31 March 2019 Voyager 2 is at a distance of 114.45 AU from Earth. The probe was moving at a velocity of 3.25 AU/year relative to the Sun on its way to interstellar space in 2013. It's moving at a velocity of 15.4 km/s relative to the Sun as of December 2014. Voyager 2 is expected to provide the first direct measurements of the density and temperature of the interstellar plasma. New Horizons was launched directly into a hyperbolic escape trajectory, getting a gravitational assist from Jupiter en route. By March 7, 2008, New Horizons was traveling outward at 3.9 AU per year. It will, slow to an escape velocity of only 2.5 AU per year as it moves away from the Sun, so it will never catch up to either Voyager.
As of early 2011, it was traveling at 3.356 AU/year relative to the Sun. On July 14, 2015, it completed a flyby of Pluto at a distance of about 33 AU from the Sun. New Horizons is expected to encounter 2014 MU69 on January 2019, at about 43.4 AU from the Sun. The Heliosphere's termination shock was crossed by Voyager 1 at 94 astronomical units and Voyager 2 at 84 AU according to the IBEX mission. If New Horizons can reach the distance of 100 AU, it will be traveling at about 13 km/s, around 4 km/s slower than Voyager 1 at that distance; the last successful reception of telemetry from Pioneer 10 was on April 27, 2002, when it was at a distance of 80.22 AU, traveling at about 2.54 AU/year. Routine mission operations for Pioneer 11 were stopped September 30, 1995, when it was 6.5 billion km from Earth, traveling at about 2.4 AU/year. New Horizons' third stage, a STAR-48 booster, is on a similar escape trajectory out of the Solar System as New Horizons, but will pass millions of kilometers from Pluto.
It crossed Pluto's orbit in October 2015. The third stage rocket boosters for Pioneer 10, for Voyager 1 and 2 are on escape trajectories out of the Solar System. In the early 2000s many new large planetary bod