Diameter km
Distance from primary km
Mass >0.01 M[1]
<6 M[2][3][lower-alpha 1]

Kepler-37b is an extrasolar planet (exoplanet) orbiting Kepler-37 in the constellation Lyra.[4] Template:As of it is the smallest planet discovered around a main-sequence star, with a radius slightly greater than that of the Moon.[5] The measurements do not constrain its mass, but masses above a few times that of the Moon give unphysically high densities.[3]


File:A Moon-size Line Up.jpg

Kepler-37b, along with two other planets, Kepler-37c and Kepler-37d, were discovered by the Kepler space telescope, which observes stellar transits.[6][7] After observing transits of Kepler-37b, astronomers had to compare it with the size of the parent star.

The size of the star was obtained using asteroseismology;Template:Clarify[8] Kepler-37 is currently the smallest star to be studied using this process.[7] This allowed the size of Kepler-37b to be determined "with extreme accuracy".[7]

To date, Kepler-37b is the smallest planet discovered around a main-sequence star[lower-alpha 2] outside the Solar System.[5] Detection of Kepler-37b was possible due to its short orbital period, relative brightness, and low activity of its host star, allowing brightness data to average out quickly.[9] The discovery of Kepler-37b has led Jack Lissauer, a scientist at NASA's Ames Research Center, to conjecture that "such little planets are common".[7]



Kepler-37b is located approximately 210 light-years from Earth.[10] It is slightly larger than the Moon, with a diameter of about 3,900 kilometres (2,400 mi).[8] NASA states that it probably has no atmosphere and cannot support life.[7] Furthermore, it is most likely composed of rocky materials.[7] Because it is so close to its star (Mercury is more than three times as far from the Sun), Kepler-37b's mean temperature is estimated to be around 425 °C (800 °F).[7]


The innermost known planet in its system, Kepler-37b, orbits its parent star at a distance of about 15 million kilometers (9.3 million miles), with a period of roughly 13 days.[5] The outer two planets in the system have orbital periods[6][11] within one percent of the 8:5 and 3:1 resonances with Kepler-37b's period.

See alsoEdit


  1. Masses more than a few times that of the Moon result in unphysically high densities.
  2. The pulsar planet PSR B1257+12 A has a comparable mass. The actual size of PSR B1257+12 A is unknown, but is likely comparable to Kepler-37b.


  3. 3.0 3.1 [1]
  4. Smallest Alien Planet Kepler-37b Explained (Infographic)
  5. 5.0 5.1 5.2 Tiniest Planet Yet Discovered by NASA Outside our Solar System. (February 21, 2013). Retrieved February 21, 2013.
  6. 6.0 6.1 (2013-02-20)A sub-Mercury-sized exoplanet. Nature (journal) 494 (7438): 452–4.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 NASA's Kepler Mission Discovers Tiny Planet System. NASA (February 20, 2013). Retrieved February 21, 2013.
  8. 8.0 8.1 Astronomers Find the Tiniest Exoplanet Yet. Slate (February 20, 2013). Retrieved February 21, 2013.
  9. Centauri Dreams - Small Planets Confirm Kepler’s Capabilities
  10. NASA, using Kepler space telescope, finds smallest planet yet. Los Angeles Times (February 20, 2013). Retrieved February 21, 2013.
  11. Cite error: Invalid <ref> tag; no text was provided for refs named keplernasa


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Template:Kepler-37 Template:Exoplanets Template:2013 in space

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