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Exoplanet List of exoplanets
Kepler-61b new.jpg
Artist's impression of Kepler-61b (foreground) as a borderline super-Earth/mini-Neptune planet, along with its host star (upper right).
Parent star
Star Kepler-61 (KOI-1361)
Constellation Cygnus
Right ascension (α) 19h 41m 13s
Declination (δ) +42° 28′ 31″
Apparent magnitude (mV) 15
Distance 1024 ly
(326 pc)
Spectral type K7V[1]
Mass (m) 0.635 (± 0.037)[1] M
Radius (r) 0.62 (± 0.03)[1] R
Temperature (T) 4017 +68
[1] K
Metallicity [Fe/H] 0.03 (± 0.14)[1]
Age >1[1] Gyr
Physical characteristics
Mass (m) 6.65[2] M
Radius (r) 2.15 (± 0.13)[1] R
Stellar flux (F) 1.27
Temperature (T) 273 K (0 °C; 32 °F)
Orbital elements
Semi-major axis (a) 0.26 AU
Eccentricity (e) <0.25
Orbital period (P) 59.87756 d
Inclination (i) >89.80°
Discovery information
Discovery date April 24, 2013[3]
Discoverer(s) Kepler spacecraft
Discovery method Transit
Discovery status Submitted
Other designations
KOI-1361.01, K01361.01, WISE J194113.07+422831.1 b, KIC 6960913 b, 2MASS J19411308+4228310 b, KOI-1361 b
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

Kepler-61b (also known by its Kepler Object of Interest designation KOI-1361.01) is a super-Earth exoplanet orbiting within parts of the habitable zone of the K-type main-sequence star Kepler-61. It is located about 1,064 light-years (326 parsecs, or nearly 1.006×1016 km) from Earth in the constellation of Cygnus. It was discovered in 2013 using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured, by NASA's Kepler team.[3]


Mass, radius and temperature[edit]

Kepler-61b is a super-Earth, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the ice giants Neptune and Uranus. Its surface temperature is 273 K (0 °C; 32 °F). It has a radius of 2.15 R, above the estimated radius of ≤1.6 R where it would likely be a mini-Neptune with a volatile composition, with no solid surface.[4] The mass of Kepler-61b is 6.65 M.

Host star[edit]

The planet orbits a (K-type) star named Kepler-61. The star has a mass of 0.63 M and a radius of 0.62 R. It has a temperature of 4017 K and is about 1 billion years old. In comparison, the Sun is 4.6 billion years old[5] and has a temperature of 5778 K.[6]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 15. Therefore, it is too dim to be seen with the naked eye.


Kepler-61b orbits its host star with about 8% of the Sun's luminosity with an orbital period of 59.877 days and an orbital radius of about 0.28 times that of Earth's (compared to Mercury from the Sun, which is about 0.38 AU). It has an eccentricity of near 0.25, meaning its orbit is mildly elliptical.


Artist's representation of an exoplanet that only passes through the habitable zone on part of its orbit.

Kepler-61b is located in the inner part of the empirical habitable zone, a zone where liquid water could exist with high albedo, relatively low humidity and higher atmospheric pressure.[7] However, the planet is likely tidally locked because of its close distance to its host star.

It has an estimated average temperature of 273 K (0 °C; 32 °F), very close to that of Earth. If Kepler-61b is Earth-like it is a good candidate for life, because the system is about one billion years old, however because of its radius (2.24 R), it is likely gaseous, with no solid surface. However, this does not totally destroy the chances of habitability in the Kepler-61 system. Kepler-61b may well have a substantially large enough Earth-like moon (with the proper atmospheric properties and pressure), capable of supporting surface liquid water, and potentially life.[8] However, such moons do not form naturally, it would have to be captured.

However, the orbit of Kepler-61b may play a key in preventing it and the hypothetical moon from being habitable. The eccentricity of the planet is 0.25, which means it has an elliptical orbit. Kepler-61b's orbit takes it slightly beyond the inner edge of the habitable zone and then out to the middle of it, which would result in the planet experiencing temperatures of up to 310 K (37 °C; 98 °F) at is closest point in its orbit, and as low as 240 K (−33 °C; −28 °F) at its farthest point.[9] These temperatures may vary if Kepler-61b has an intense greenhouse effect, resulting in the planet being too hot to support liquid water all together.


In 2009, NASA's Kepler spacecraft was completing observing stars on its photometer, the instrument it uses to detect transit events, in which a planet crosses in front of and dims its host star for a brief and roughly regular period of time. In this last test, Kepler observed 50000 stars in the Kepler Input Catalog, including Kepler-61; the preliminary light curves were sent to the Kepler science team for analysis, who chose obvious planetary companions from the bunch for follow-up at observatories. The radial velocity observations confirmed that a planetary body was responsible for the dips observed in Kepler-61's light curve, thus confirming it as a planet. It was announced on April 24, 2013.[3]

See also[edit]

  • Gliese 832 c – similar exoplanet in the habitable zone with an eccentric orbit with various temperature swings


  1. ^ a b c d e f g "Kepler-61b". Retrieved July 20, 2016. 
  2. ^ PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo
  3. ^ a b c Exoplanet Characterization by Proxy: a Transiting 2.15 R_Earth Planet Near the Habitable Zone of the Late K dwarf Kepler-61 Sarah Ballard, David Charbonneau, Francois Fressin, Guillermo Torres, Jonathan Irwin, Jean-Michel Desert, Elisabeth Newton, Andrew W. Mann, David R. Ciardi, Justin R. Crepp, Christopher E. Henze, Stephen T. Bryson, Steven B. Howell, Elliott P. Horch, Mark E. Everett, Avi Shporer et al. April 26, 2013
  4. ^
  5. ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011. 
  6. ^ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011. 
  7. ^ Zsom, Andras; Seager, Sara; De Wit, Julien (April 2013). "Towards the Minimum Inner Edge Distance of the Habitable Zone". The Astrophysical Journal 1304 (2): 3714. arXiv:1304.3714. Bibcode:2013ApJ...778..109Z. doi:10.1088/0004-637X/778/2/109. 
  8. ^ David A. Weintraub. Religions and Extraterrestrial Life: How Will We Deal With It?. Springer. p. 64. ISBN 978-3-319-05056-0. 
  9. ^

External links[edit]

Coordinates: Sky map 19h 41m 13s, +42° 28′ 31″