There are 3,903 known exoplanets, or planets outside our solar system that orbit a star, as of December 1, 2018; 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 56 exoplanets listed as confirmed by the NASA Exoplanet Archive. [a] Among the over 400 known stars within 10 parsecs, [b] 29 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.
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.
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]
|°||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||30||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).
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).
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).