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List of smallest exoplanets

Topic: Astronomy

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A size comparison of the planets in the Kepler-37 system and objects in the Solar System

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

List

This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by expanding it with reliably sourced entries.

The sizes are listed in units of Earth radii (R⊕). 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.[1][2] Radii listed in italics are estimates.

Exoplanet Radius (R⊕) Notes and references
SDSS J0845+2257 b 0.01-0.013 Planetesimal, enhanced in iron and silicates. [3]
WD 1145+017 b ~0.03[4] Disintegrating planetesimal, likely one of several orbiting its star. Likely about one-tenth the mass of Ceres and ~200 km in radius.[4]
Ceres 0.0742 Shown for comparison
Pluto 0.1863 Shown for comparison
Moon 0.2725 Shown for comparison
Kepler-37b 0.3098+0.0059
−0.0076 		Smallest known exoplanet.[5][6]
BD+05 4868 Ab ~0.314 Disintegrating planet, radius is just an estimate.[7]
PSR B1257+12 b (Draugr) ~0.338 Least massive known exoplanet, at 0.02 Earth masses. Radius predicted from mass-radius relationship.[8]
Kepler-1520b ≲0.36 Disintegrating planets with poorly known radii, all thought to be smaller than Mercury.[9][10]
KOI-2700b
K2-22b
Mercury 0.3826 Shown for comparison
Kepler-879c 0.4±0.1 [11]
Kepler-444b 0.403+0.016
−0.014 		[12]
Ganymede 0.413 Shown for comparison
Kepler-158d 0.43±0.05 [11]
Kepler-102b 0.460±0.026 [6]
Kepler-444c 0.497+0.021
−0.017 		[12]
Kepler-1971b (KOI-4777.01) 0.51±0.03 [13]
Kepler-1489c 0.51±0.08 [11]
Kepler-1994b 0.51+0.06
−0.05 		[14]
Kepler-1308b 0.52+0.06
−0.05
Kepler-444d 0.530+0.022
−0.019 		[12]
Mars 0.5325 Shown for comparison
Kepler-62c 0.54±0.03
Kepler-444e 0.546+0.017
−0.015 		[12]
Gliese 238 b 0.566±0.014 [15]
Kepler-102c 0.567±0.028 [6]
Kepler-42d 0.57±0.18
Kepler-1583b 0.60+0.09
−0.05
Kepler-1998b 0.6+0.08
−0.04 		[16]
Kepler-963c 0.6±0.2 [11]
Kepler-974c (KOI-1843.03) 0.61+0.12
−0.08 		Candidate.[17] As of 2025, the Exoplanet Archive lists it as confirmed.[2]
Kepler-1087b 0.61+0.17
−0.05
K2-89b 0.615±0.080
Kepler-1877b 0.624
Barnard's Star e ~0.637 Radius predicted from mass-radius relationship.[2] Least massive exoplanet detected by radial velocity and possibly smallest known within 10 parsecs.[18]
K2-137b 0.64±0.10[19] The discovery paper finds a larger radius of 0.89±0.09 R🜨[20]
Kepler-1371c 0.64+0.07
−0.05
Kepler-138b 0.64±0.02 [21]
Kepler-1130d 0.645
Kepler-1351b 0.65+0.05
−0.04
Kepler-1542c 0.65+0.09
−0.06
Kepler-271d 0.66±0.05
Kepler-431c 0.668
Kepler-1558b 0.68+0.06
−0.04
LHS 1678 b 0.685+0.037
−0.035 		[22]
K2-116b 0.69±0.04
Kepler-141b 0.69±0.05
K2-297b (EPIC 201497682 b) 0.692+0.059
−0.048
Proxima Centauri d ~0.692 Radius predicted from mass-radius relationship.[2][23]
Barnard's Star d ~0.694 Radius predicted from mass-radius relationship.[2][18]
Gliese 367 b (Tahay) 0.699±0.024 Smallest exoplanet within 10 parsecs with a measured radius.[24]
Kepler-2003b (KOI-4978.02) 0.7±0.1 [11]
Kepler-378c 0.70±0.05

Excluded objects

Kepler-37e is listed with a radius of 0.37±0.18 R🜨 in the Exoplanet Archive based on KOI data, but the existence of this planet is doubtful,[25] and assuming its existence, a 2023 study found a mass of 8.1±1.7 M🜨, inconsistent with such a small radius.[26]

KOI-6705.01, listed as a potential very small planet in the KOI dataset, was shown to be a false positive in 2016.[27]

Candidate planets

Below is a list of candidate planets below 0.7 R⊕. These planets have yet to be confirmed.

Kepler object of interest Radius (R⊕) Notes and references
SDSS J1228+1040 b
(SDSS J122859.92+104033.0 b, WD 1226+110 b) 		0.010+0.0504−0.0085[28][29]
TRAPPIST-1i 0.228+0.025
−0.032[30]
KOI-4582.01 0.35[31]
KOI-2298.03 0.36[31]
KOI-2169.04 0.37[31]
KOI-7174.01 0.37[31]
KOI-8012.01 0.42[31]
KOI-6860.01 0.43[31]
KOI-2059.02 0.44[31]
KOI-304.02 0.46[31]
KOI-7793.01 0.46[31]
KOI-2678.02 0.48[31]
KOI-6631.01 0.48[31]
KOI-2421.02 0.48[31]
KOI-5974.01 0.49[31]
KOI-3444.03 0.5[31]
KOI-2295.01 0.52[31]
KOI-7863.01 0.52[31]
KOI-2612.02 0.53[31]
KOI-4657.01 0.54[31]
KOI-8257.01 0.54[31]
KOI-115.03 (Kepler-105d) 0.55+0.08
−0.07 		[32]
KOI-2421.01 0.55[31]
KOI-4097.02 0.55[31]
KOI-7645.01 0.55[31]
KOI-3208.01 0.56[31]
KOI-6763.01 0.56[31]
KOI-2859.03 0.57[31]
KOI-4146.02 0.57[31]
KOI-2859.04 0.57[31]
KOI-7873.01 0.57[31]
TOI-4307.02 0.57±0.14[33]
KOI-2657.01 0.58[31]
KOI-8277.01 0.58[31]
KOI-4296.01 0.59[31]
KOI-3196.01 0.59[31]
KOI-5692.01 0.59[31]
KOI-1964.01 0.6[31]
KOI-4407.01 0.6[31]
KOI-4871.01 0.6[31]
KOI-5211.01 0.6[31]
KOI-7888.01 0.6[31]
KOI-3184.03 0.6[31]
KOI-8183.01 0.6[31]
KOI-3083.02 0.61[31]
KOI-4421.01 0.61[31]
KOI-4716.01 0.61[31]
KOI-3102.01 0.61[31]
KOI-7032.01 0.61[31]
KOI-1499.02 0.62[31]
KOI-605.02 0.62[31]
KOI-7676.01 0.62[31]
KOI-4849.01 0.62[31]
KOI-365.02 0.62[31]
KOI-7116.01 0.62[31]
KOI-4421.02 0.62[31]
KOI-7949.01 0.62[31]
KOI-2029.04 0.63[31]
KOI-6889.01 0.63[31]
KOI-2636.02 0.63[31]
KOI-3248.01 0.64[31]
KOI-5213.01 0.64[31]
KOI-6276.01 0.64[31]
KOI-7617.01 0.64[31]
KOI-7903.01 0.64[31]
KOI-7925.01 0.64[31]
KOI-8174.01 0.64[31]
KOI-3083.03 0.65[31]
KOI-4875.01 0.65[31]
KOI-4808.01 0.65[31]
KOI-6568.01 0.65[31]
KOI-1619.01 0.66[31]
KOI-3111.02 0.66[31]
KOI-2859.05 0.66[31]
KOI-3017.01 0.67[31]
KOI-4907.01 0.67[31]
KOI-1616.02 0.67[31]
KOI-6299.01 0.67[31]
KOI-8211.01 0.67[31]
KOI-2593.02 0.68[31]
KOI-4605.01 0.68[31]
KOI-7832.01 0.68[31]
KOI-7483.01 0.68[31]
KOI-2623.02 0.68[31]
KOI-7924.01 0.68[31]
KOI-7628.01 0.69[31]
KOI-4129.01 0.69[31]
KOI-4822.01 0.69[31]
KOI-6600.01 0.69[31]

See also

References

  1. ↑ Staff (10 July 2017). "Exoplanet Catalog". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/. Retrieved 10 July 2017. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 "Planetary Systems Composite Data". https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PSCompPars. Retrieved 13 March 2025. 
  3. ↑ Wilson, D. J.; Gänsicke, B. T.; Koester, D.; Toloza, O.; Pala, A. F.; Breedt, E.; Parsons, S. G. (2015). "The composition of a disrupted extrasolar planetesimal at SDSS J0845+2257 (Ton 345)". Monthly Notices of the Royal Astronomical Society 451 (3): 3237–3248. doi:10.1093/mnras/stv1201. Bibcode: 2015MNRAS.451.3237W. https://academic.oup.com/mnras/article/451/3/3237/1197266?login=false. 
  4. ↑ 4.0 4.1 Rappaport, S.; Gary, B. L. (June 2016). "Drifting asteroid fragments around WD 1145+017". Monthly Notices of the Royal Astronomical Society 458 (4): 3904–3917. doi:10.1093/mnras/stw612. Bibcode: 2016MNRAS.458.3904R. 
  5. ↑ Simukoff, E. et al. (2013). "Below One Earth Mass: The Detection, Formation, and Properties of Subterrestrial Worlds". Space Science Reviews 180 (1–4): 71. doi:10.1007/s11214-013-0019-1. Bibcode: 2013SSRv..180...71S. 
  6. ↑ 6.0 6.1 6.2 Bonomo, A. S. et al. (September 2023). "Cold Jupiters and improved masses in 38 Kepler and K2 small planet systems from 3661 HARPS-N radial velocities. No excess of cold Jupiters in small planet systems". Astronomy & Astrophysics 677: A33. doi:10.1051/0004-6361/202346211. Bibcode: 2023A&A...677A..33B. 
  7. ↑ Hon, Marc; Rappaport, Saul; Shporer, Avi; Vanderburg, Andrew; Collins, Karen A.; Watkins, Cristilyn N.; Schwarz, Richard P.; Barkaoui, Khalid et al. (2025-01-09). "A Disintegrating Rocky Planet with Prominent Comet-like Tails Around a Bright Star". The Astrophysical Journal 984 (1): L3. doi:10.3847/2041-8213/adbf21. Bibcode: 2025ApJ...984L...3H. 
  8. ↑ "Exoplanet-catalog". 22 April 2019. https://exoplanets.nasa.gov/exoplanet-catalog/7134/psr-b125712-b/. 
  9. ↑ Ansdell, M.; Hirano, T.; Gaidos, E. (2019). "Monitoring of the D doublet of neutral sodium during transits of two 'evaporating' planets". Monthly Notices of the Royal Astronomical Society 485 (3): 3876–3886. doi:10.1093/mnras/stz693. Bibcode: 2019MNRAS.485.3876G. "[...]the radii are not known but are thought to be smaller than Mercury (0.36R⊕).". 
  10. ↑ Garai, Z. (2018). "Light-curve analysis of KOI 2700b: The second extrasolar planet with a comet-like tail". Astronomy & Astrophysics 611: A63. doi:10.1051/0004-6361/201629676. Bibcode: 2018A&A...611A..63G. "We confirmed the disintegrating-planet scenario of KOI 2700b.". 
  11. ↑ 11.0 11.1 11.2 11.3 11.4 Wang, Kaitlyn et al. (November 2024). "Discovery of small ultra-short-period planets orbiting Kepler KG dwarfs with GPU phase folding and deep learning". Monthly Notices of the Royal Astronomical Society 534 (3): 1913–1927. doi:10.1093/mnras/stae2155. Bibcode: 2024MNRAS.534.1913W. 
  12. ↑ 12.0 12.1 12.2 12.3 Campante, T. et al. (2015). "KOI-3158: The oldest known system of terrestrial-size planets". EPJ Web of Conferences 101: 02004. doi:10.1051/epjconf/201510102004. Bibcode: 2015EPJWC.10102004C. 
  13. ↑ Cañas, Caleb I.; Mahadevan, Suvrath; Cochran, William D.; Bender, Chad F.; Feigelson, Eric D.; Harman, C. E.; Kopparapu, Ravi Kumar; Caceres, Gabriel A. et al. (2022). "A Hot Mars-sized Exoplanet Transiting an M Dwarf". The Astronomical Journal 163 (1): 3. doi:10.3847/1538-3881/ac3088. Bibcode: 2022AJ....163....3C. 
  14. ↑ "Kepler-1994". https://exoplanetarchive.ipac.caltech.edu/overview/Kepler-1994%20b. Retrieved 16 June 2023. 
  15. ↑ Tey, Evan et al. (May 2024). "GJ 238 b: A 0.57 Earth Radius Planet Orbiting an M2.5 Dwarf Star at 15.2 pc". The Astronomical Journal 167 (6): 283. doi:10.3847/1538-3881/ad3df1. Bibcode: 2024AJ....167..283T. 
  16. ↑ "Kepler-1998". https://exoplanetarchive.ipac.caltech.edu/overview/Kepler-1998%20b. Retrieved 16 June 2023. 
  17. ↑ Price, Ellen M.; Rogers, Leslie A. (May 2020). "Tidally Distorted, Iron-enhanced Exoplanets Closely Orbiting Their Stars". The Astrophysical Journal 894 (1): 8. doi:10.3847/1538-4357/ab7c67. Bibcode: 2020ApJ...894....8P. 
  18. ↑ 18.0 18.1 Basant, Ritvik et al. (March 2025). "Four Sub-Earth Planets Orbiting Barnard's Star from MAROON-X and ESPRESSO". The Astrophysical Journal Letters 982 (1): L1. doi:10.3847/2041-8213/adb8d5. Bibcode: 2025ApJ...982L...1B. 
  19. ↑ Adams, Elisabeth R. et al. (August 2021). "Ultra-short-period Planets in K2. III. Neighbors are Common with 13 New Multiplanet Systems and 10 Newly Validated Planets in Campaigns 0-8 and 10". The Planetary Science Journal 2 (4): 152. doi:10.3847/PSJ/ac0ea0. Bibcode: 2021PSJ.....2..152A. 
  20. ↑ Smith, A. M. S. et al. (March 2018). "K2-137 b: an Earth-sized planet in a 4.3-h orbit around an M-dwarf". Monthly Notices of the Royal Astronomical Society 474 (4): 5523–5533. doi:10.1093/mnras/stx2891. Bibcode: 2018MNRAS.474.5523S. 
  21. ↑ Piaulet, Caroline et al. (15 December 2022). "Evidence for the volatile-rich composition of a 1.5-Earth-radius planet". Nature Astronomy 7: 206. doi:10.1038/s41550-022-01835-4. Bibcode: 2023NatAs...7..206P. 
  22. ↑ Silverstein, Michele L. et al. (May 2024). "Validation of a Third Planet in the LHS 1678 System". The Astronomical Journal 167 (6): 255. doi:10.3847/1538-3881/ad3040. Bibcode: 2024AJ....167..255S. 
  23. ↑ Suárez Mascareño, Alejandro et al. (29 July 2025). "Diving into the planetary system of Proxima with NIRPS: Breaking the metre per second barrier in the infrared". Astronomy & Astrophysics 700: A11. doi:10.1051/0004-6361/202553728. Bibcode: 2025A&A...700A..11S. 
  24. ↑ Goffo, Elisa et al. (September 2023). "Company for the ultra-high density, ultra-short period sub-Earth GJ 367 b: discovery of two additional low-mass planets at 11.5 and 34 days". The Astrophysical Journal Letters 955 (1): L3. doi:10.3847/2041-8213/ace0c7. Bibcode: 2023ApJ...955L...3G. 
  25. ↑ Rajpaul, V. M.; Buchhave, L. A.; Lacedelli, G.; Rice, K.; Mortier, A.; Malavolta, L.; Aigrain, S.; Borsato, L. et al. (2021), "A HARPS-N mass for the elusive Kepler-37d: A case study in disentangling stellar activity and planetary signals", Monthly Notices of the Royal Astronomical Society 507 (2): 1847–1868, doi:10.1093/mnras/stab2192, Bibcode: 2021MNRAS.507.1847R 
  26. ↑ Weiss, Lauren M. et al. (2024-01-01). "The Kepler Giant Planet Search. I. A Decade of Kepler Planet-host Radial Velocities from W. M. Keck Observatory". The Astrophysical Journal Supplement Series 270 (1). doi:10.3847/1538-4365/ad0cab. Bibcode: 2024ApJS..270....8W. 
  27. ↑ Gaidos, Eric; Mann, Andrew W.; Ansdell, Megan (January 2016). "The Enigmatic and Ephemeral M Dwarf System KOI 6705: Cheshire Cat or Wild Goose?". The Astrophysical Journal 817 (1): 50. doi:10.3847/0004-637X/817/1/50. Bibcode: 2016ApJ...817...50G. 
  28. ↑ Manser, Christopher J. (5 April 2019). "A planetesimal orbiting within the debris disc around a white dwarf star". Science 364 (6435): 66–69. doi:10.1126/science.aat5330. ISSN 0036-8075. PMID 30948547. Bibcode: 2019Sci...364...66M. https://www.science.org/doi/10.1126/science.aat5330. 
  29. ↑ "Planet SDSS J1228+1040 b". Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/sdss_j1228_1040_b--7079/. Retrieved 2019-08-05. 
  30. ↑ "First JWST thermal phase curves of temperate terrestrial exoplanets reveal no thick atmosphere around TRAPPIST-1 b and c". 2 September 2025. arXiv:2509.02128 [astro-ph.EP].
  31. ↑ 31.00 31.01 31.02 31.03 31.04 31.05 31.06 31.07 31.08 31.09 31.10 31.11 31.12 31.13 31.14 31.15 31.16 31.17 31.18 31.19 31.20 31.21 31.22 31.23 31.24 31.25 31.26 31.27 31.28 31.29 31.30 31.31 31.32 31.33 31.34 31.35 31.36 31.37 31.38 31.39 31.40 31.41 31.42 31.43 31.44 31.45 31.46 31.47 31.48 31.49 31.50 31.51 31.52 31.53 31.54 31.55 31.56 31.57 31.58 31.59 31.60 31.61 31.62 31.63 31.64 31.65 31.66 31.67 31.68 31.69 31.70 31.71 31.72 31.73 31.74 31.75 31.76 31.77 31.78 31.79 31.80 31.81 31.82 31.83 31.84 "NASA Exoplanet Archive". https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=cumulative. Retrieved 16 June 2023. 
  32. ↑ "Kepler-105". https://exoplanetarchive.ipac.caltech.edu/overview/KOI-115. Retrieved 12 December 2021. 
  33. ↑ "NASA Exoplanet Archive". https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=TOI. Retrieved 16 June 2023. 



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