List of smallest exoplanets

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A size comparison of the planets in the Kepler-37 system and objects in the Solar System A Moon-size Line Up.jpg
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.

Contents

List

This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources.

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]

ExoplanetRadius (R🜨)Notes and references
SDSS J1228+1040 b
(SDSS J122859.92+104033.0 b, WD 1226+110 b)		0.010+0.0504
−0.0085 [3] [4] 		Extrasolar planetesimal. Likely a remnant iron core. Radius is in the range of 1.2 –120 km. [3]
WD 1145+017 b ~0.03 [5] Disintegrating planetesimal, likely one of several orbiting its star. Likely about one-tenth the mass of Ceres and ~200 km in radius. [5]
Ceres 0.0742Shown for comparison
Pluto 0.1863Shown for comparison
Moon 0.2725Shown for comparison
Kepler-37b 0.3098+0.0059
−0.0076		Smallest known exoplanet. [6] [7]
PSR B1257+12 b (Draugr)~0.338Least massive known exoplanet, at 0.02 Earth masses. Radius estimated from mass-radius relationship. [8]
Kepler-1520b ≲0.36Disintegrating planets with poorly known radii, all thought to be smaller than Mercury. [9] [10]
KOI-2700b
K2-22b
Mercury 0.3826Shown for comparison
Kepler-444b 0.403+0.016
−0.014		 [11]
Ganymede 0.413Shown for comparison
Kepler-102b 0.460±0.026 [7]
Kepler-444c 0.497+0.021
−0.017		 [11]
Kepler-1971b (KOI-4777.01)0.51±0.03 [12]
Kepler-1994b 0.51+0.06
−0.05		 [13]
Kepler-1308b 0.52+0.06
−0.05
Kepler-444d 0.530+0.022
−0.019		 [11]
Mars 0.5325Shown for comparison
Kepler-62c 0.54±0.03
Kepler-444e 0.546+0.017
−0.015		 [11]
Gliese 238 b 0.566±0.014 [14]
Kepler-102c 0.567±0.028 [7]
Kepler-42d 0.57±0.18
Kepler-1583b 0.60+0.09
−0.05
Kepler-1998b 0.6+0.08
−0.04		 [15]
Kepler-1087b 0.61+0.17
−0.05
K2-89b 0.615±0.080
Kepler-1877b 0.624
K2-137b 0.64±0.10
Kepler-1371c 0.64+0.07
−0.05
Kepler-138b 0.64±0.02 [16]
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		 [17]
K2-116b 0.69±0.04
Kepler-141b 0.69±0.05
K2-297b (EPIC 201497682 b)0.692+0.059
−0.048
Gliese 367 b (Tahay)0.699±0.024Smallest known exoplanet within 10 parsecs. [18]
Kepler-1349b 0.700+0.630
−0.110
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, [19] and assuming its existence, a 2023 study found a mass of 8.1±1.7  M🜨 , inconsistent with such a small radius. [20]

KOI-6705.01, listed as a potential very small planet in the KOI dataset, was shown to be a false positive in 2016. [21]

Kepler and TESS candidates

Below shows a list of Kepler and TESS candidates below 0.7 R🜨 that have yet to be confirmed.

Kepler object of interestRadius (R🜨)Notes and references
KOI-4582.010.35 [22]
KOI-2298.030.36 [22]
KOI-2169.040.37 [22]
KOI-7174.010.37 [22]
KOI-8012.010.42 [22]
KOI-6860.010.43 [22]
KOI-2059.020.44 [22]
KOI-304.020.46 [22]
KOI-7793.010.46 [22]
KOI-2678.020.48 [22]
KOI-6631.010.48 [22]
KOI-2421.020.48 [22]
KOI-5974.010.49 [22]
KOI-3444.030.5 [22]
KOI-2295.010.52 [22]
KOI-7863.010.52 [22]
KOI-2612.020.53 [22]
KOI-4657.010.54 [22]
KOI-8257.010.54 [22]
KOI-115.03 (Kepler-105d)0.55+0.08
−0.07		 [23]
KOI-2421.010.55 [22]
KOI-4097.020.55 [22]
KOI-7645.010.55 [22]
KOI-3208.010.56 [22]
KOI-6763.010.56 [22]
KOI-2859.030.57 [22]
KOI-4146.020.57 [22]
KOI-2859.040.57 [22]
KOI-7873.010.57 [22]
TOI-4307.020.57±0.14 [24]
KOI-2657.010.58 [22]
KOI-8277.010.58 [22]
KOI-4296.010.59 [22]
KOI-3196.010.59 [22]
KOI-5692.010.59 [22]
KOI-1964.010.6 [22]
KOI-4407.010.6 [22]
KOI-4871.010.6 [22]
KOI-5211.010.6 [22]
KOI-7888.010.6 [22]
KOI-3184.030.6 [22]
KOI-8183.010.6 [22]
KOI-3083.020.61 [22]
KOI-4421.010.61 [22]
KOI-4716.010.61 [22]
KOI-3102.010.61 [22]
KOI-7032.010.61 [22]
KOI-1843.030.61+0.12
−0.08		 [25]
KOI-1499.020.62 [22]
KOI-605.020.62 [22]
KOI-7676.010.62 [22]
KOI-4849.010.62 [22]
KOI-365.020.62 [22]
KOI-7116.010.62 [22]
KOI-4421.020.62 [22]
KOI-7949.010.62 [22]
KOI-2029.040.63 [22]
KOI-6889.010.63 [22]
KOI-2636.020.63 [22]
KOI-3248.010.64 [22]
KOI-5213.010.64 [22]
KOI-6276.010.64 [22]
KOI-7617.01 0.64 [22]
KOI-7903.010.64 [22]
KOI-7925.010.64 [22]
KOI-8174.010.64 [22]
KOI-3083.030.65 [22]
KOI-4875.010.65 [22]
KOI-4808.010.65 [22]
KOI-6568.010.65 [22]
KOI-1619.010.66 [22]
KOI-3111.020.66 [22]
KOI-2859.050.66 [22]
KOI-3017.010.67 [22]
KOI-4907.010.67 [22]
KOI-1616.020.67 [22]
KOI-6299.010.67 [22]
KOI-8211.010.67 [22]
KOI-2593.020.68 [22]
KOI-4605.010.68 [22]
KOI-7832.010.68 [22]
KOI-7483.010.68 [22]
KOI-2623.020.68 [22]
KOI-7924.010.68 [22]
KOI-7628.010.69 [22]
KOI-4129.010.69 [22]
KOI-4822.010.69 [22]
KOI-6600.010.69 [22]

See also

Related Research Articles

<span class="mw-page-title-main">Super-Earth</span> Type of exoplanet

A Super-Earth is a type of exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.

A Kepler object of interest (KOI) is a star observed by the Kepler space telescope that is suspected of hosting one or more transiting planets. KOIs come from a master list of 150,000 stars, which itself is generated from the Kepler Input Catalog (KIC). A KOI shows a periodic dimming, indicative of an unseen planet passing between the star and Earth, eclipsing part of the star. However, such an observed dimming is not a guarantee of a transiting planet, because other astronomical objects—such as an eclipsing binary in the background—can mimic a transit signal. For this reason, the majority of KOIs are as yet not confirmed transiting planet systems.

Kepler-20 is a star about 934 light-years from Earth in the constellation Lyra with a system of at least five, and possibly six, known planets. The apparent magnitude of this star is 12.51, so it cannot be seen with the unaided eye. Viewing it requires a telescope with an aperture of 15 cm (6 in) or more. It is slightly smaller than the Sun, with 94% of the Sun's radius and about 91% of the Sun's mass. The effective temperature of the photosphere is slightly cooler than that of the Sun at 5466 K, giving it the characteristic yellow hue of a stellar class G8 star. The abundance of elements other than hydrogen or helium, what astronomers term the metallicity, is approximately the same as in the Sun. It may be older than the Sun, although the margin of error here is relatively large.

<span class="mw-page-title-main">Kepler-42</span> Red dwarf star in the constellation Cygnus

Kepler-42, formerly known as KOI-961, is a red dwarf located in the constellation Cygnus and approximately 131 light years from the Sun. It has three known extrasolar planets, all of which are smaller than Earth in radius, and likely also in mass.

Kepler-102 is a star 353 light-years away in the constellation of Lyra. Kepler-102 is less luminous than the Sun. The star system does not contain any observable amount of dust. Kepler-102 is suspected to be orbited by a binary consisting of two red dwarf stars, at projected separations of 591 and 627 AU.

<span class="mw-page-title-main">Kepler-138</span> Red dwarf in the constellation Lyra

Kepler-138, also known as KOI-314, is a red dwarf located in the constellation Lyra, 219 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission used to detect planets transiting their stars.

K2-3, also known as EPIC 201367065, is a red dwarf star with three known planets. It is on the borderline of being a late orange dwarf/K-type star, but because of its temperature, it is classified as a red dwarf.

<span class="mw-page-title-main">Kepler-444</span> Triple star system in the constellation of Lyra

Kepler-444 is a triple star system, estimated to be 11.2 billion years old, approximately 119 light-years (36 pc) away from Earth in the constellation Lyra. On 27 January 2015, the Kepler spacecraft is reported to have confirmed the detection of five sub-Earth-sized rocky exoplanets orbiting the main star. The star is a K-type main sequence star. All of the planets are far too close to their star to harbour life forms.

The small planet radius gap is an observed scarcity of planets with radii between 1.5 and 2 times Earth's radius, likely due to photoevaporation-driven mass loss. A bimodality in the Kepler exoplanet population was first observed in 2011 and attributed to the absence of significant gas atmospheres on close-in, low-mass planets. This feature was noted as possibly confirming an emerging hypothesis that photoevaporation could drive atmospheric mass loss This would lead to a population of bare, rocky cores with smaller radii at small separations from their parent stars, and planets with thick hydrogen- and helium-dominated envelopes with larger radii at larger separations. The bimodality in the distribution was confirmed with higher-precision data in the California-Kepler Survey in 2017, which was shown to match the predictions of the photoevaporative mass-loss hypothesis later that year.

<span class="mw-page-title-main">TOI-700 d</span> Goldilocks terrestrial planet orbiting TOI-700

TOI-700 d is a near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf TOI-700, the outermost planet within the system. It is located roughly 101.4 light-years (31.1 pc) away from Earth in the constellation of Dorado. The exoplanet is the first Earth-sized exoplanet in the habitable zone discovered by the Transiting Exoplanet Survey Satellite (TESS).

Kepler-1544b is a potentially habitable exoplanet announced in 2016 and located 1138 light years away, in the constellation of Cygnus.

References

  1. ↑ Staff (10 July 2017). "Exoplanet Catalog". Extrasolar Planets Encyclopaedia . Retrieved 10 July 2017.
  2. ↑ "Planetary Systems Composite Data". NASA Exoplanet Archive . Retrieved 16 July 2023.
  3. 1 2 Manser, Christopher J.; et al. (5 April 2019). "A planetesimal orbiting within the debris disc around a white dwarf star". Science. 364 (6435): 66–69. arXiv: 1904.02163 . Bibcode:2019Sci...364...66M. doi:10.1126/science.aat5330. ISSN   0036-8075. PMID   30948547. S2CID   96434522.
  4. ↑ "Planet SDSS J1228+1040 b". Extrasolar Planets Encyclopaedia . Retrieved 2019-08-05.
  5. 1 2 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. arXiv: 1602.00740 . Bibcode:2016MNRAS.458.3904R. doi:10.1093/mnras/stw612.
  6. ↑ Simukoff, E.; et al. (2013). "Below One Earth Mass: The Detection, Formation, and Properties of Subterrestrial Worlds". Space Science Reviews. 180 (1–4): 71. arXiv: 1308.6308 . Bibcode:2013SSRv..180...71S. doi:10.1007/s11214-013-0019-1. S2CID   118597064.
  7. 1 2 3 Bonomo, A. S.; Dumusque, X.; 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. arXiv: 2304.05773 . Bibcode:2023A&A...677A..33B. doi:10.1051/0004-6361/202346211. S2CID   258078829.
  8. ↑ "Exoplanet-catalog".
  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. arXiv: 1903.06217 . Bibcode:2019MNRAS.485.3876G. doi:10.1093/mnras/stz693. [...]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. arXiv: 1712.07461 . Bibcode:2018A&A...611A..63G. doi:10.1051/0004-6361/201629676. S2CID   118885868. We confirmed the disintegrating-planet scenario of KOI 2700b.
  11. 1 2 3 4 Campante, T.; et al. (2015). "KOI-3158: The oldest known system of terrestrial-size planets". EPJ Web of Conferences. 101: 02004. arXiv: 1501.07869 . Bibcode:2015EPJWC.10102004C. doi:10.1051/epjconf/201510102004. S2CID   16191462.
  12. ↑ Cañas, Caleb I.; Mahadevan, Suvrath; Cochran, William D.; Bender, Chad F.; Feigelson, Eric D.; Harman, C. E.; Kopparapu, Ravi Kumar; Caceres, Gabriel A.; Diddams, Scott A.; Endl, Michael; Ford, Eric B.; Halverson, Samuel; Hearty, Fred; Jones, Sinclaire; Kanodia, Shubham; Lin, Andrea S. J.; Metcalf, Andrew J.; Monson, Andrew; Ninan, Joe P.; Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita; Schwab, Christian; Stefánsson, Guđmundur (2022). "A Hot Mars-sized Exoplanet Transiting an M Dwarf". The Astronomical Journal. 163 (1): 3. arXiv: 2112.03958 . Bibcode:2022AJ....163....3C. doi: 10.3847/1538-3881/ac3088 . S2CID   244954104.
  13. ↑ "Kepler-1994". NASA Exoplanet Archive . Retrieved 16 June 2023.
  14. ↑ Tey, Evan; Shporer, Avi; 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 .
  15. ↑ "Kepler-1998". NASA Exoplanet Archive . Retrieved 16 June 2023.
  16. ↑ Piaulet, Caroline; Benneke, Björn; et al. (15 December 2022). "Evidence for the volatile-rich composition of a 1.5-Earth-radius planet". Nature Astronomy . 7: 206. arXiv: 2212.08477 . Bibcode:2023NatAs...7..206P. doi:10.1038/s41550-022-01835-4. S2CID   254764810.
  17. ↑ Silverstein, Michele L.; Barclay, Thomas; et al. (May 2024). "Validation of a Third Planet in the LHS 1678 System". The Astronomical Journal . 167 (6): 255. arXiv: 2403.00110 . Bibcode:2024AJ....167..255S. doi: 10.3847/1538-3881/ad3040 .
  18. ↑ Goffo, Elisa; Gandolfi, Davide; 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. arXiv: 2307.09181 . Bibcode:2023ApJ...955L...3G. doi: 10.3847/2041-8213/ace0c7 .
  19. ↑ Rajpaul, V. M.; Buchhave, L. A.; Lacedelli, G.; Rice, K.; Mortier, A.; Malavolta, L.; Aigrain, S.; Borsato, L.; Mayo, A. W.; Charbonneau, D.; Damasso, M.; Dumusque, X.; Ghedina, A.; Latham, D. W.; López-Morales, M.; Magazzù, A.; Micela, G.; Molinari, E.; Pepe, F.; Piotto, G.; Poretti, E.; Rowther, S.; Sozzetti, A.; Udry, S.; Watson, C. A. (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, arXiv: 2107.13900 , Bibcode:2021MNRAS.507.1847R, doi:10.1093/mnras/stab2192
  20. ↑ 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) 8. arXiv: 2304.00071 . Bibcode: 2024ApJS..270....8W . doi: 10.3847/1538-4365/ad0cab .
  21. ↑ 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. arXiv: 1511.06471 . Bibcode:2016ApJ...817...50G. doi: 10.3847/0004-637X/817/1/50 .
  22. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 "NASA Exoplanet Archive". NASA Exoplanet Archive . Retrieved 16 June 2023.
  23. ↑ "Kepler-105". NASA Exoplanet Archive . Retrieved 12 December 2021.
  24. ↑ "NASA Exoplanet Archive". NASA Exoplanet Archive . Retrieved 16 June 2023.
  25. ↑ Price, Ellen M.; Rogers, Leslie A. (May 2020). "Tidally Distorted, Iron-enhanced Exoplanets Closely Orbiting Their Stars". The Astrophysical Journal . 894 (1): 8. arXiv: 1901.10666 . Bibcode:2020ApJ...894....8P. doi: 10.3847/1538-4357/ab7c67 .
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