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.
The most distant potentially habitable planet confirmed is Kepler-1606b, at 2,870 light-years distant,[2] 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 unconfirmed 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 planet inconclusive.[9]
Star with the faintest apparent magnitude with a planet
The candidate for the most massive planet is contentious, as it is difficult to distinguish between a highly massive planet and a brown dwarf (the border between them approximately from 13 to 80 MJ). It is estimated the largest planets are approximately a dozen Jupiter masses.
The densities of Kepler-51 b and c have been constrained to be below 0.05 g/cm3 (expected value 0.03 g/cm3 for each). The density of Kepler-51d is determined to be 0.046 ± 0.009 g/cm3.[19]
2MASS J04414489+2301513 b is listed as the youngest planet in the NASA Exoplanet Archive, at a age of 1 Myr,[4] but fails the mass ratio criterion of the IAU working definition of an exoplanet; the mass ratio with the primary is smaller than ~1/25[29] and 'more likely to have produced' 'by cloud core fragmentation' (like a star).[30]
K2-33b is the youngest transiting planet, at an age of 9.3 Myr.[31]
[38] Record among confirmed planets. The disproven planet candidate at VB 10 was thought to have a higher eccentricity of 0.98.[39]HD 80606 b previously held this record at 0.93226+0.00064 −0.00069.
ROXs 42B (AB) b is lower in mass at 9.0+6 −3MJ, however also in projected separation of ≈150 AU.[48]
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.[49]
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.[47]
FW Tauri b orbits at a projected separation of 330±30 AU around a ≈11 AU separated binary.[50] It was shown to be more likely a 0.1 M☉ star surrounded by a protoplanetary disk than a planetary-mass companion.[51]
Closest orbit between stars with a planet orbiting one of the stars
BD+20°2457 may be the lowest-metallicity planet host ([Fe/H]=−1.00); however, the proposed planetary system is dynamically unstable.[53]
Planets were announced around even the extremely low-metallicity stars HIP 13044 and HIP 11952; however, these claims have since been disproven.[54]
A brown dwarf or massive gas giant companion was announced around the population II star HE 1523-0901, whose metallicity is −2.65±0.22 dex.[55] 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.[56]
M51-ULS-1b, listed as a candidate planet with 4 sigma confidence, may be the planet with the highest-mass host star.[58] The stars R126 (HD 37974) and R66 (HD 268835) in the Large Magellanic Cloud have masses of 70 and 30 solar masses and have dust discs but no planets have been detected yet.
HD 81817 and Mirach (β Andromedae) are larger, at 83.8±7.8 R☉[4] and 86.4 R☉[60] respectively, but their planetary companions may actually be brown dwarfs, and in the case of HD 81817 its companion may be sufficiently massive to be a red dwarf. R Leonis (299 or 320-350 R☉)[61][62] has a candidate planet. It is a Mira variable.
The stars R126 and R66 in the Large Magellanic Cloud have radius of 78 R☉ and 131 R☉[63] and have dust discs but no planets have been detected yet.
[69][41] With a mass of 28.26+2.05 −2.17MJ, the planet is likely a brown dwarf. Beta Cancri, with a luminosity of 794 L☉, is the most luminous star to host a planet (Beta Cancri b) that is not a potential brown dwarf.[70][41]
The stars R126 and R66 in the Large Magellanic Cloud have luminosity of 1400000L☉ and 320000L☉[63] 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.[75] 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, but as the star is a supergiant, does not count as on the main sequence.
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.[76] The four planets Tau Ceti e, f, g and h are considered as strong candidates.[77]
HD 10180 has six confirmed planets and potentially three more planets.[78]
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.[80]
Multiplanetary system with smallest mean semi-major axis (planets are nearest to their star)
Kepler-42 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.[4] 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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