The following are lists of extremes among the known exoplanets. The properties listed here are those for which values are known reliably. It is important to note that the study of exoplanets is one of the most dynamic emerging fields of science, and these values may change wildly as new discoveries are made.
Several candidate extragalactic planets have been detected. Assuming the largest distance value from the microlensing light-curve, the planet OGLE-2017-BLG-0364Lb might be more distant, at around 32,600 light-years (10,000 pc).[2]
The most distant potentially habitable planet confirmed is Kepler-1606b, at 2,870 light-years distant,[3] although the unconfirmed planet KOI-5889.01 is over 5,000 light-years distant.
Proxima Centauri b and d are the closest rocky exoplanets, b is the closest potentially habitable exoplanet known, and c is the closest mini-Neptune and potentially ringed planet. As Proxima Centauri is the closest star to the Sun (and will stay so for the next 25,000 years), this is an absolute record.
Alpha Centauri A (apparent magnitude 0.01) has an planet candidate. The evidence of planets around Vega with an apparent magnitude of 0.03 is strongly suggested by circumstellar disks surrounding it.[7] As of 2021[update], a candidate planet around Vega has been detected.[8]
Aldebaran (apparent magnitude varies between 0.75 and 0.95) was suspected to have a candidate planet, however later studies found the existence of the planet inconclusive.[9]Pollux (apparent magnitude 1.14[10]) has a reported planet (Thestias), but the existence of this planet has been questioned.[11][12] Mirfak (α Per, apparent magnitude 1.806) was claimed to have an orbiting planet, whose existence has likewise been disputed.[13]
A 2023 study detected 10 luminous point sources around the primary star of Fomalhaut system (apparent magnitude = 1.16), of which the last source may be either an unrelated background object or a planetary-mass companion.[14]
Star with the faintest apparent magnitude with a planet
The most massive planet is difficult to define due to the blurry line between planets and brown dwarfs. If the borderline is defined as the deuterium fusion threshold (roughly 13MJ at solar metallicity[16][b]), the most massive planets are those with true mass closest to that cutoff; if planets and brown dwarfs are differentiated based on formation, their mass ranges overlap.[17][18]: 62 A candidate for the most massive object that formed in a protoplanetary disk is HD 206893 b, at about 28MJ. Both this object and its 13MJ sibling HD 206893 c fuse deuterium.[19][20]
According to the IAU working definition of exoplanetsPSR J1719−1438 b, being slightly more massive than Jupiter, is an exoplanet, despite it possibly formed like a white dwarf from a yellow dwarf star and suffered from the influence of the host star to become a carbon-rich diamond-like object. For reference, it is about as dense or denser than Osmium at 293 K, the densest naturally occurring element on Earth.
TOI-4603b is the next densest with 14.1+1.7 −1.6 g/cm3,[28] a mass of 12.89+0.58 −0.57 MJ and a radius of 1.042+0.038 −0.035 RJ.[29]
KELT-1b is similarly dense with 22.1+5.62 −9.16 g/cm3.[30] But, with a mass of 27.23 MJ, it is likely a brown dwarf. Kepler-131c might be more dense at 77.7+55 −55 g/cm3,[31] but the value is highly uncertain.
The bulk density of Kepler-51 d has been constrained to be 0.038 ± 0.006 g/cm3.[33] Next least dense are the Hot SaturnHAT-P-67 with about 0.044 g/cm3 and the super-Neptune planet WASP-193b, with 0.059 ± 0.014 g/cm3.[34]
The free-floating planet or sub-brown dwarf Proplyd 133-353 is younger, at 0.5 Myr.[42][43] However, as a free-floating planet, it does not meet the IAU's working definition of a planet.[44]
2MASS J04414489+2301513 b is listed as the youngest planet in the NASA Exoplanet Archive, at an age of 1 Myr,[5] but fails the mass ratio criterion of the IAU working definition of an exoplanet; the mass ratio with the primary is larger than the L4/L5 limit of stability ≈ 1/25[44] and 'more likely to have been produced by cloud core fragmentation' (like a star).[45]
A substellar object announced around the pulsar SWIFT J1756.9−2508 may have a shorter orbital period of under an hour, around 54 minutes.[51]M62H b has an orbit almost exactly 1 hour longer.[52] A planetary-mass object orbiting the white dwarf GP Comae Berenices has an even shorter orbital period of 46 minutes and is sometimes listed as an exoplanet.[53] However, it is more likely the remaining core of a former white dwarf being highly disrupted.[54]
K2-137b has the shortest orbit around a main-sequence star (an M dwarf) at 4.31 hours.[55]
UCAC4 328-061594 b has an even longer orbital separation (19 000 AU), although its mass (21 MJ) [5][56] is higher than the deuterium burning limit (13 MJ).
Another candidate around BD+29 5007 has an even larger orbit of about 22 100 AU. There is no consensus about its age and resulting mass, yet.
The companion of ASASSN-21js has an orbit of 13 000 AU, but it is unknown if it is a brown dwarf or a planet due to its unknown mass.[57]
[60] Record among confirmed planets. The disproven planet candidate at VB 10 was thought to have a higher eccentricity of 0.98.[61]HD 80606 b previously held this record at 0.93226+0.00064 −0.00069.
UCAC4 328-061594 b has an even longer orbital separation (19,000 AU), although its mass (21MJ)[5][56] is higher than the deuterium burning limit (13MJ).
ROXs 42B (AB) b is lower in mass at 9.0+6 −3MJ, however also in projected separation of ≈150 AU.[69]
DT Virginis c, also known as Ross 458 (AB) c, at a projected separation of ≈1200 AU, with several mass estimates below the deuterium burning limit, has a latest mass determination of 27±4MJ.[70]
Largest orbit around a single star in a multiple star system
SR 12 (AB) c has a mass of 0.013±0.007 M☉ at a projected separation of ≈1100 AU.[68]
FW Tauri b orbits at a projected separation of 330±30 AU around a ≈11 AU separated binary.[71] It was shown to be more likely a 0.1 M☉ star surrounded by a protoplanetary disk than a planetary-mass companion.[72]
DMPP-3 Ab's semi-major axis is around 0.067 AU. The next closest orbit between stars with an S-type planet occurs in Nu Octantis system, of which the separation between the stellar components is 2.629 AU.[75]
Smallest semi-major axis ratio between consecutive planets
BD+20°2457 may be the lowest-metallicity planet host ([Fe/H]=−1.00); however, the proposed planetary system is dynamically unstable.[76]
Planets were announced around even the extremely low-metallicity stars HIP 13044 and HIP 11952; however, these claims have since been disproven.[77]
A brown dwarf or massive planetary companion was announced around the population II star HE 1523-0901, whose metallicity is −2.65±0.22 dex.[78] While the inclination of the companion is not known, if its orbit is nearly face-on, it would be sufficiently massive to become a red dwarf instead.[79]
M51-ULS-1b, listed as a candidate planet with 4 sigma confidence, may be the planet with the highest-mass host star.[81] The stars R126 (HD 37974), R66 (HD 268835) and HH 1177 in the Large Magellanic Cloud have masses of 70, 30 and 15 solar masses and have dust discs[82] but no planets have been detected yet.
Other stars, such as HD 18438, Mirach and Delta Virginis are larger, but their substellar companions are more massive than the deuterium burning limit (13MJ), and thus might be brown dwarfs rather than exoplanets.[5]
This is the most luminous star to host a planet that is not a potential brown dwarf.[63]
The star Mirfak, whose luminosity is 3780 L☉,[93] was claimed to have an orbiting planet with a minimum mass of 6.6 ± 0.2 Jupiter masses. However, the existence of the planet is doubtful.[13] R Leonis (at 3537 L☉)[84] has a candidate planet. R Fornacis (at 5800 L☉)[85] also has a candidate planet. The bright giant BD+20°2457 (at 1479 L☉[94]) was believed to have two planetary-mass companions orbiting although the claimed system configuration is dynamically unstable.[76]
The stars R126 and R66 in the Large Magellanic Cloud have luminosity of 1400000L☉ and 320000L☉[87] and have dust discs but no planets have been detected yet.
V921 Scorpii b orbits a hotter star, at 30,000 K. Its host star is a 20-solar-mass B0IV-class subgiant.[100] However, at 60 Jupiter masses, it is not considered a planet under most definitions.
The candidate planet M51-ULS-1b's supergiant primary is an O5-class supergiant with an estimated surface temperature of 40,000 K.
Tau Ceti currently has no confirmed planetary companion, although it has been proposed that the number of orbiting planets may be 8, 9 or even 10.[101] The four planets Tau Ceti e, f, g and h are considered as strong candidates.[102]
HD 10180 has six confirmed planets and potentially three more planets.[103]
30 Arietis Bb was believed to be either brown dwarf or a massive gas giant in a quadruple star system until later studies revealed a true mass well above 80 MJup.[105]
The quintuple star system GG Tauri has several protoplanetary disks but no planets have been detected yet.[106]
Multiplanetary system with smallest mean semi-major axis (planets are nearest to their star)
Kepler-429 b, c and d have a semi-major axis of only 0.0116, 0.006 and 0.0154 AU, respectively. The separation between closest and furthest is only 0.0094 AU.
Kepler-70 b, c and d (all unconfirmed and disputed) have a semi-major axis of only 0.006, 0.0076 and ~0.0065 AU, respectively. The separation between closest and furthest is only 0.0016 AU (239,356 km).
Multiplanetary system with largest range of semi-major axis (largest difference between the star's nearest planet and its farthest planet)
The planets in the Kepler-444 system have radii of 0.4, 0.497, 0.53, 0.546 and 0.741 Earth radii, respectively. Due to their size and proximity to Kepler-444, these must be rocky planets, with masses close to that of Mars. For comparison, Mars has a mass of 0.105 Earth masses and a radius of 0.53 Earth radii.
The planets in the Kepler-444 system have radii of 0.4, 0.497, 0.53, 0.546 and 0.741 Earth radii, respectively. Due to their size and proximity to Kepler-444, these must be rocky planets, with masses close to that of Mars. For comparison, Mars has a mass of 0.105 Earth masses and a radius of 0.53 Earth radii.
Multiplanetary system with largest mean planetary mass
Nu Ophiuchi b and c have masses of 22.206 and 24.662 Jupiter masses, respectively.[5] They may be brown dwarfs.
Exo-multiplanetary system with smallest range in planetary mass, log scale (smallest proportional difference between the most and least massive planets)
Mercury and Jupiter have a mass ratio of 5,750 to 1. Kepler-37 d and b may have a mass ratio between 500 and 1,000, and Gliese 676 c and d have a mass ratio of 491.
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^Gamma Leonis is mentioned to have a slightly higher magnitude (1.99), but it is the combined magnitude of the system and not of the planet-hosting star. The true apparent magnitude is 2.37.
^The deuterium burning limit also depends on the metallicity and abundance of helium. Metal-rich planets, for example, need a lower mass to fuse deuterium.
^Based on the estimated temperature and luminosity.
^A normal star is a star that is past its protostar period, in its main fusion period, before becoming a degenerate star, black hole, or post-stellar nebula, and is not a brown dwarf