There are 3,976 known exoplanets, or planets outside our solar system that orbit a star, as of February 1, 2019; only a small fraction of these are located in the vicinity of the Solar System. Within 10 parsec s (32.6 light-year s), there are 57 exoplanets listed as confirmed by the NASA Exoplanet Archive. [a] Among the over 400 known stars within 10 parsecs, [b] 30 have been confirmed to have planetary systems; 51 stars in this range are visible to the naked eye, [c] nine of which have planetary systems.
An exoplanet or extrasolar planet is a planet outside the Solar System. The first evidence of an exoplanet was noted in 1917, but was not recognized as such. The first scientific detection of an exoplanet was in 1988; it was confirmed to be an exoplanet in 2012. The first confirmed detection occurred in 1992. As of 1 April 2019, there are 4,023 confirmed planets in 3,005 systems, with 656 systems having more than one planet.
The Solar System is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury.
The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System. A parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond, which corresponds to 648000/π astronomical units. One parsec is equal to about 3.26 light-years or 31 trillion kilometres (31×1012 km) or 19 trillion miles (19×1012 mi). The nearest star, Proxima Centauri, is about 1.3 parsecs (4.2 light-years) from the Sun. Most of the stars visible to the unaided eye in the night sky are within 500 parsecs of the Sun.
The first report of an exoplanet within this range was in 1998 for a planet orbiting around Gliese 876 (15.3 light-years (ly) away), and the latest as of 2017 is one around Ross 128 (11 ly). The closest exoplanet found is Proxima Centauri b, which was confirmed in 2016 to orbit Proxima Centauri, the closest star to our Solar System (4.25 ly). HD 219134 (21.6 ly) has six exoplanets, the highest number discovered for any star within this range. A planet around Fomalhaut (25 ly) was, in 2008, the first planet to be directly imaged.
Gliese 876 is a red dwarf approximately 15 light-years away from Earth in the constellation of Aquarius. It is the one of the closest known stars to the Sun confirmed to possess a planetary system and the fifth closest such system known to consist of multiple planets. As of 2018, four extrasolar planets have been found to orbit the star. The planetary system is also notable for the orbital properties of its planets. It is the only known system of orbital companions to exhibit a triple conjunction in the rare phenomenon of Laplace resonance. It is also the first extrasolar system around a normal star with measured coplanarity. Two of the middle planets are located in the system's habitable zone; however, they are giant planets believed to be analogous to Jupiter.
Ross 128 is a red dwarf in the equatorial zodiac constellation of Virgo, near β Virginis. The apparent magnitude of Ross 128 is 11.13, which is too faint to be seen with the unaided eye. Based upon parallax measurements, the distance of this star from Earth is 10.89 light-years, making it the twelfth closest stellar system to the Solar System. It was first cataloged in 1926 by American astronomer Frank Elmore Ross.
Proxima Centauri b is an exoplanet orbiting in the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. It is located about 4.2 light-years from Earth in the constellation of Centaurus, making it the closest known exoplanet to the Solar System.
Most known nearby exoplanets orbit close to their star and have highly eccentric orbits. A majority are significantly larger than Earth, but a few have similar masses, including two planets (around YZ Ceti, 12 ly) which may be less massive than Earth. Several confirmed exoplanets are hypothesized to be potentially habitable, with Proxima Centauri b and three around Gliese 667 C (23.6 ly) considered the most likely candidates.The International Astronomical Union took a public survey in 2015 about renaming some known extrasolar bodies, including the planets around Epsilon Eridani (10.5 ly) and Fomalhaut. [d]
The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit, 1 is a parabolic escape orbit, and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a Klemperer rosette orbit through the galaxy.
YZ Ceti is a red dwarf star in the constellation Cetus. Although it is relatively close to the Sun at just 12 light years, this star cannot be seen with the naked eye. It is classified as a flare star that undergoes intermittent fluctuations in luminosity. YZ Ceti is about 13 percent the mass of the Sun and 17% of its radius.
The International Astronomical Union is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy. Among other activities, it acts as the internationally recognized authority for assigning designations and names to celestial bodies and any surface features on them.
|°||Mercury, Earth and Jupiter (for comparison purposes)|
|#||Confirmed multiplanetary systems|
|↑||Exoplanets believed to be potentially habitable|
|Host star system||Companion exoplanet (in order from star)||Notes and additional planetary observations|
|Name|| Distance |
| Mass |
| Semi-major axis |
| Orbital period |
| Eccentricity || Inclination |
|Proxima Centauri||4.2441||11.13||0.123||b ↑||>1.3||~1.1||0.0485||11.2||<0.35||—||2016|
|Epsilon Eridani||10.446||3.73||0.83||AEgir||500||—||3.39||2,500||0.70||~25?||2000||1 inferred planet and a disc|
|Ross 128||11.007||11.1||0.168||b ↑||>1.4||~1.2||0.0496||9.87||0.12||—||2017|
|Tau Ceti #||11.753||3.50||0.78||g||>1.7||—||0.133||20.0||0.06||—||2017||2 retracted and 1 candidate|
|YZ Ceti #||12.108||12.1||0.130||b||>0.75||—||0.0156||1.97||0.0||—||2017||1 candidate|
|Luyten's Star #||12.199||11.94||0.29||c||>1.2||—||0.0365||4.72||0.17||—||2017|
|Kapteyn's Star||12.829||8.8||0.28||c||>7||—||0.311||122||0.23||—||2014||1 candidate|
|Wolf 1061 #||14.046||10.1||0.25||b||>1.9||—||0.0375||4.89||0.15||—||2015|
|Gliese 876 #||15.250||10.2||0.33||d||6.8||—||0.0208||1.94||0.21||59||2005|
|Gliese 832 #||16.194||8.67||0.45||c ↑||>5.4||~1.7||0.163||35.7||0.18||—||2014|
|40 Eridani A||16.386||4.4||0.84||Ab||>8.5||—||0.224||42.4||0.04||~72?||2018|
|LHS 1723 #||17.533||12.2||0.164||b ↑||>2.0||~1.3||0.0328||5.36||0.2||—||2017|
|Gliese 752 A||19.286||9.13||0.46||Ab||>12.2||—||0.336||106||0.16||—||2018|
|82 G. Eridani #||19.582||4.26||0.85||b||>2.7||—||0.121||18.3||~0||—||2011||2 candidates|
|Gliese 581 #||20.545||10.5||0.31||e||>1.7||—||0.0282||3.15||0.0||~45?||2009||2 disputed candidates and a disc |
|HD 219134 #||21.306||5.57||0.78||b||4.7||1.60||0.0388||3.09||~0||85||2015||1 candidate, 2 dubious planets|
|Gliese 667 #||23.632||10.2||0.33||Cb||>5.6||—||0.051||7.20||~0.1||~52?||2009||5 dubious candidates|
|61 Virginis #||27.741||4.74||0.95||b||>5.1||—||0.0502||4.22||~0.1||~77?||2009||a debris disc |
|HD 192310 #||28.699||6.13||0.78||b||>17||—||0.32||75||0.13||—||2010|
|Gliese 176||30.879||10.1||0.45||b||>9.1||—||0.066||8.78||0.15||—||2007||1 dubious planet|
Unlike for bodies within our Solar System, there is no clearly established method for officially recognizing an exoplanet. According to the International Astronomical Union, an exoplanet should be considered confirmed if it has not been disputed for five years after its discovery.There have been examples where the existence of exoplanets has been proposed, but even after follow-up studies their existence is still considered doubtful by some astronomers. Such cases include: Alpha Centauri (4.36 ly, two in 2012 and 2013 ), Lalande 21185 (8.31 ly, in 2017 ), Groombridge 34 (11.7 ly, two in 2014 and 2017 ), Epsilon Indi (11.8 ly, in 2018 ), LHS 288 (15.6 ly, in 2007 ), 40 Eridani (16.3 ly, in 2018 ), Gliese 682 (16.6 ly, two in 2014 ), and Gliese 229 (18.8 ly, in 2014 ). There are also some instances where proposed exoplanets were later disproved by subsequent studies, such as candidates around Teegarden's star (12.6 ly), Van Maanen 2 (13.9 ly), Groombridge 1618 (15.9 ly), and VB 10 (18.7 ly).
Alpha Centauri is the closest star system and closest planetary system to the Solar System at 4.37 light-years (1.34 pc) from the Sun. It is a triple star system, consisting of three stars: α Centauri A, α Centauri B, and α Centauri C.
Lalande 21185 is a star in the constellation of Ursa Major, relevant for being the brightest red dwarf observable in the northern hemisphere. Despite this, and although relatively close by, it is very dim, being only magnitude 7.5 in visible light and thus too dim to be seen with the unaided eye. The star is visible through a small telescope or binoculars.
Epsilon Indi is a star system approximately 12 light-years from Earth in the constellation of Indus consisting of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it. The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf (T1) and ε Indi Bb a late T dwarf (T6) separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.
The Working Group on Extrasolar Planets of the International Astronomical Union adopted in 2003 a working definition on the upper limit for what constitutes a planet: not being massive enough to sustain thermonuclear fusion of deuterium. Some studies have calculated this to be somewhere around 13 times the mass of Jupiter, and therefore objects more massive than this are usually classified as brown dwarfs.Some proposed candidate exoplanets were later shown to be massive enough to fall above the threshold, and are likely brown dwarfs, as was the case for: SCR 1845-6357 B (12.6 ly), SDSS J1416+1348 B (29.7 ly), and WISE 1217+1626 B (30 ly).
Deuterium is one of two stable isotopes of hydrogen. The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutron in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom in 6420 of hydrogen. Thus deuterium accounts for approximately 0.0156% of all the naturally occurring hydrogen in the oceans, while protium accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another.
A brown dwarf is a type of substellar object occupying the mass range between the heaviest gas giant planets and the lightest stars, having a mass between approximately 13 to 75–80 times that of Jupiter (MJ), or approximately 2.5×1028 kg to about 1.5×1029 kg. Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.
SDSS J1416+1348 is a nearby wide binary system of two brown dwarfs, located in constellation Boötes. The system consists of L-type component A and T-type component B.
Excluded from the current list are known examples of potential free-floating sub-brown dwarfs, or "rogue planets", which are bodies that are too small to undergo fusion yet they do not revolve around a star. Known such examples include: WISE 0855–0714 (7.3 ly),UGPS 0722-05, (13 ly) WISE 1541−2250 (18.6 ly), and SIMP J01365663+0933473 (20 ly).
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs but that has a mass below the limiting mass for thermonuclear fusion of deuterium . Some researchers call them free-floating planets whereas others call them planetary-mass brown dwarfs.
A rogue planet is a planetary-mass object that orbits a galactic center directly. Such objects have been ejected from the planetary system in which they formed or have never been gravitationally bound to any star or brown dwarf. The Milky Way alone may have billions of rogue planets.
WISE 1541−2250 is a sub-brown or brown dwarf of spectral class Y0.5, located in the constellation Libra at approximately 18.6 light-years from Earth. This object received popular attention when its discovery was announced in 2011 at a distance estimated to be only about 9 light-years, which would have made it the closest brown dwarf known.. It is not the farthest known Y-type brown dwarf to Earth.
|Distance (ly)||# of known|
|# of known|
|# of stars|
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
Fomalhaut, also designated Alpha Piscis Austrini is the brightest star in the constellation of Piscis Austrinus and one of the brightest stars in the sky. It is a class A star on the main sequence approximately 25 light-years (7.7 pc) from the Sun as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk. Fomalhaut, K-type main-sequence star TW Piscis Austrini, and M-type, red dwarf star LP 876-10 constitute a triple system, even though the companions are separated by several degrees.
PSR B1257+12, previously designated PSR 1257+12, alternatively designated PSR J1300+1240, also named Lich, is a pulsar located 2,300 light-years from the Sun in the constellation of Virgo.
Gliese 436 is a red dwarf approximately 31.8 light-years away in the zodiac constellation of Leo. It has an apparent visual magnitude of 10.67, which is much too faint to be seen with the naked eye. However, it can be viewed with even a modest telescope of 2.4 in (6 cm) aperture. In 2004, the existence of an extrasolar planet, Gliese 436b, was verified as orbiting the star. This planet was later discovered to transit its host star.
HD 187123 is an 8th magnitude G-type main sequence star located approximately 150 light-years away in the constellation of Cygnus. Like our Sun, it is a yellow dwarf. Being at a distance of about 160 light-years it is not visible to the unaided eye. However, it should be easy target with binoculars or small telescope.
WASP or Wide Angle Search for Planets is an international consortium of several academic organisations performing an ultra-wide angle search for exoplanets using transit photometry. The array of robotic telescopes aims to survey the entire sky, simultaneously monitoring many thousands of stars at an apparent visual magnitude from about 7 to 13.
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the extrasolar planets reported as of April 2014 have been observed directly, with even fewer being resolved from their host star.
Gliese 436 b is a Neptune-sized exoplanet orbiting the red dwarf Gliese 436. It was the first hot Neptune discovered with certainty and was among the smallest-known transiting planets in mass and radius, until the much smaller Kepler exoplanet discoveries started coming in by 2010.
A hot Neptune or Hoptune is a type of giant planet with a mass similar to that of Uranus or Neptune orbiting close to its star, normally within less than 1 AU. The first hot Neptune to be discovered with certainty was Gliese 436 b in 2007, an exoplanet about 33 light years away. Recent observations have revealed a larger potential population of hot Neptunes in the Milky Way than was previously thought. Hot Neptunes may have formed either in situ or ex situ.
Fomalhaut b, also known as Dagon, is a confirmed, directly imaged extrasolar object and candidate planet orbiting the A-type main-sequence star Fomalhaut, approximately 25 light-years away in the constellation of Piscis Austrinus. The object was initially announced in 2008 and confirmed as real in 2012 from images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope and, according to calculations reported in January 2013, has a 1,700-year, highly elliptical orbit. It has a periastron of 7.4 billion km and an apastron of about 44 billion km. As of May 25, 2013 it is 110 AU from its parent star.
HR 8799 c is an extrasolar planet located approximately 129 light-years away in the constellation of Pegasus, orbiting the 6th magnitude Lambda Boötis star HR 8799. This planet has a mass between 5 and 10 Jupiter masses and a radius from 20 to 30% larger than Jupiter's. It orbits at 38 AU from HR 8799 with an unknown eccentricity and a period of 190 years; it is the 2nd planet discovered in the HR 8799 system. Along with two other planets orbiting HR 8799, this planet was discovered on November 13, 2008 by Marois et al., using the Keck and the Gemini observatories in Hawaii. These planets were discovered using the direct imaging technique. In January 2010, HR 8799 c became the 3rd exoplanet to have a portion of its spectrum directly observed, confirming the feasibility of direct spectrographic studies of exoplanets.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized at first. However, the first scientific detection of an exoplanet began in 1988. Afterwards, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 1 April 2019, there are 4,023 confirmed planets in 3,005 systems, with 656 systems having more than one planet. This is a list of the most notable discoveries.
The NASA Exoplanet Archive is an online astronomical exoplanet catalog and data service that collects and serves public data that support the search for and characterization of extra-solar planets (exoplanets) and their host stars. It is part of the Infrared Processing and Analysis Center and is on the campus of the California Institute of Technology (Caltech) in Pasadena, CA. The archive is funded by NASA and was launched in early December 2011 by the NASA Exoplanet Science Institute as part of NASA's Exoplanet Exploration Program. In July 2017, the archive's collection of confirmed exoplanets surpassed 3,500.
Kepler-296e is a confirmed Earth-sized exoplanet orbiting within the habitable zone of Kepler-296. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the discovery of the exoplanet on 26 February 2014.
OGLE-2007-BLG-349(AB)b is a circumbinary extrasolar planet about 8,000 light-years away in the constellation of Sagittarius. It is the first circumbinary exoplanet to be discovered using the microlensing method of detecting exoplanets.