List of smallest exoplanets explained

Below is a list of the smallest exoplanets so far discovered, in terms of physical size, ordered by radius.

List

The sizes are listed in units of Earth radii . All planets listed are smaller than Earth and Venus, up to 0.7 Earth radii. The NASA Exoplanet Archive is used as the main data source.

Exoplanet Radius Notes and references
SDSS J1228+1040 b
(SDSS J122859.92+104033.0 b, WD 1226+110 b)
0.010[1] Extrasolar planetesimal. Likely a remnant iron core. Radius is in the range of 1.2120 km.
WD 1145+017 b~0.03Disintegrating planetesimal, likely one of several orbiting its star. Likely about one-tenth the mass of Ceres and ~200 km in radius.
Ceres0.0742Shown for comparison
Pluto0.1863Shown for comparison
Moon0.2725Shown for comparison
Kepler-37bSmallest known exoplanet.
PSR B1257+12 b (Draugr)~0.338Least massive known exoplanet, at 0.02 Earth masses. Radius estimated from mass-radius relationship.[2]
Kepler-1520b≲0.36Disintegrating planets with poorly known radii, all thought to be smaller than Mercury.
KOI-2700b
K2-22b
Mercury0.3826Shown for comparison
Kepler-444b
Ganymede0.413Shown for comparison
Kepler-102b
Kepler-444c
Kepler-1971b (KOI-4777.01)
Kepler-1994b[3]
Kepler-1308b
Kepler-444d
Mars0.5325Shown for comparison
Kepler-62c
Kepler-444e
Gliese 238 b
Kepler-102c
Kepler-42d
Kepler-1583b
Kepler-1998b[4]
Kepler-1087b
K2-89b
Kepler-1877b0.624
K2-137b
Kepler-1371c
Kepler-138b
Kepler-1130d0.645
Kepler-1351b
Kepler-1542c
Kepler-271d
Kepler-431c0.668
Kepler-1558b
LHS 1678 b
K2-116b
Kepler-141b
K2-297b (EPIC 201497682 b)
Gliese 367 b (Tahay)Smallest known exoplanet within 10 parsecs.
Kepler-378c

Excluded objects

Kepler-37e is listed with a radius of in the Exoplanet Archive based on KOI data, but the existence of this planet is doubtful, and assuming its existence, a 2023 study found a mass of, inconsistent with such a small radius.

KOI-6705.01, listed as a potential very small planet in the KOI dataset, was shown to be a false positive in 2016.

Kepler and TESS candidates

Below shows a list of Kepler and TESS candidates below that have yet to be confirmed.

Kepler object of interestRadius Notes and references
KOI-4582.010.35
KOI-2298.030.36
KIC 1718360.010.366[5]
KOI-2169.040.37
KOI-7174.010.37
KOI-8012.010.42
KOI-6860.010.43
KOI-2059.020.44
KOI-304.020.46
KOI-7793.010.46
KOI-2678.020.48
KOI-6631.010.48
KOI-2421.020.48
KOI-5974.010.49
KOI-3444.030.5
KOI-2295.010.52
KOI-7863.010.52
KOI-2612.020.53
KOI-4657.010.54
KOI-8257.010.54
KOI-115.03 (Kepler-105d)[6]
KOI-2421.010.55
KOI-4097.020.55
KOI-7645.010.55
KOI-3208.010.56
KOI-6763.010.56
KOI-2859.030.57
KOI-4146.020.57
KOI-2859.040.57
KOI-7873.010.57
TOI-4307.02
KOI-2657.010.58
KOI-8277.010.58
KOI-4296.010.59
KOI-3196.010.59
KOI-5692.010.59
KOI-1964.010.6
KOI-4407.010.6
KOI-4871.010.6
KOI-5211.010.6
KOI-7888.010.6
KOI-3184.030.6
KOI-8183.010.6
KOI-3083.020.61
KOI-4421.010.61
KOI-4716.010.61
KOI-3102.010.61
KOI-7032.010.61
KOI-1843.03
KOI-1499.020.62
KOI-605.020.62
KOI-7676.010.62
KOI-4849.010.62
KOI-365.020.62
KOI-7116.010.62
KOI-4421.020.62
KOI-7949.010.62
KOI-2029.040.63
KOI-6889.010.63
KOI-2636.020.63
KOI-3248.010.64
KOI-5213.010.64
KOI-6276.010.64
KOI-7617.010.64
KOI-7903.010.64
KOI-7925.010.64
KOI-8174.010.64
KOI-3083.030.65
KOI-4875.010.65
KOI-4808.010.65
KOI-6568.010.65
KOI-1619.010.66
KOI-3111.020.66
KOI-2859.050.66
KOI-3017.010.67
KOI-4907.010.67
KOI-1616.020.67
KOI-6299.010.67
KOI-8211.010.67
KOI-2593.020.68
KOI-4605.010.68
KOI-7832.010.68
KOI-7483.010.68
KOI-2623.020.68
KOI-7924.010.68
KOI-7628.010.69
KOI-4129.010.69
KOI-4822.010.69
KOI-6600.010.69

See also

Notes and References

  1. Encyclopedia: Planet SDSS J1228+1040 b. Extrasolar Planets Encyclopaedia. 2019-08-05.
  2. Web site: Exoplanet-catalog.
  3. Web site: Kepler-1994. NASA Exoplanet Archive. 16 June 2023.
  4. Web site: Kepler-1998. NASA Exoplanet Archive. 16 June 2023.
  5. Roche . Jakob . The Detection of KIC 1718360, A Rotating Variable with a Possible Companion, Using Machine Learning . 2024-06-07 . astro-ph.EP . 2405.05282.
  6. Web site: Kepler-105 . . 12 December 2021.