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Kepler-186f

First Earth-sized exoplanet found in another star's habitable zone.

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Kepler-186f is an Earth-sized exoplanet candidate orbiting within the habitable zone of the red dwarf star Kepler-186, about 580 light-years from Earth in the constellation Cygnus.[1][2] The planet is about 11% larger in radius than Earth and receives about 32% of Earth's illumination from its star.[3][4]

Key facts and history

NASA's Kepler space telescope detected Kepler-186f using the transit method, requiring analysis of three years of data.[5] Kepler-186f orbits its star every 129.9 days at a distance of about 0.40 AU.[6] The four inner planets in the system are too hot for liquid water.[7] A 2019 study estimated the false positive probability for Kepler-186f at 4%, while a 2025 study estimated 20%.[8]

The Allen Telescope Array listened for radio emissions from the system for about a month as of April 2014.[9] No signals attributable to extraterrestrial technology were found during that search.[9] On 17 April 2014, the planet was announced at the same time as a paper in Science was published.[5] The host star is a red dwarf of spectral class M, with a temperature of 3755 K and an estimated age of roughly 4 billion years.[10]

What the research sources say

A NASA press release stated that Kepler-186f confirms Earth-size planets exist in habitable zones of other stars.[11] The same NASA source noted that previous research suggests a planet of this size is likely to be rocky.[11] The Guardian reported that Kepler-186f is 10% bigger than Earth and orbits the outer edge of its habitable zone.[12] The Guardian also stated that the planet may receive extra radiation from its active star.[12]

Ross (2019) wrote that Kepler-186f's surface temperature without an atmosphere is -85°C, colder than Mars.[13] Ross further noted that for liquid water to exist, the planet would need abundant carbon dioxide in its atmosphere.[13]

References

  1. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Quintana, "An Earth-Sized Planet in the Habitable Zone of a Cool Star", Science, 2014-04-18, p. 277–280; Johnson, "NASA's Kepler Discovers First Earth-Size Planet in The 'Habitable Zone' of Another Star", NASA, 17 April 2014; Burke, "Re-evaluating Small Long-period Confirmed Planets from Kepler", The Astronomical Journal, April 2019, p. 143; Chang, "Scientists Find an 'Earth Twin', or Maybe a Wife", The New York Times, 17 April 2014; Chang, "Astronomers spot most Earth-like planet yet", 17 April 2014; Morelle, "'Most Earth-like planet yet' en.wikipedia.org
  2. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Bailer-Jones, "Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2", The Astronomical Journal, August 2018, p. 58 (original not read by us) en.wikipedia.org
  3. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Quintana, "An Earth-Sized Planet in the Habitable Zone of a Cool Star", Science, 2014-04-18, p. 277–280; Johnson, "NASA's Kepler Discovers First Earth-Size Planet in The 'Habitable Zone' of Another Star", NASA, 17 April 2014; Chang, "Astronomers spot most Earth-like planet yet", 17 April 2014 (we also read that source) en.wikipedia.org
  4. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: "Kepler 186 f", hpcf.upr.edu; Quintana, "An Earth-Sized Planet in the Habitable Zone of a Cool Star", Science, 2014-04-18, p. 277–280 (original not read by us) en.wikipedia.org
  5. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Quintana, "Kepler 186f – First Earth-sized Planet Orbiting in Habitable Zone of Another Star", SETI Institute, 17 April 2014; Chang, "Astronomers spot most Earth-like planet yet", 17 April 2014; Staff, "EBI – Search for Life Beyond the Solar System 2014 – Exoplanets, Biosignatures & Instruments", EBI2014, 16 March 2014; Klotz, "Scientists Home in on Earth-Sized Exoplanet", Discovery Communications, 20 March 2014; Johnson, "NASA's Kepler Discovers First Earth-Size Planet in The 'Habitable Zone' of Another Star", NASA, 17 April 2014; Quintana en.wikipedia.org
  6. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: "Kepler-186 f", NASA Exoplanet Archive (original not read by us) en.wikipedia.org
  7. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Bolmont, "Formation, tidal evolution and habitability of the Kepler-186 system", The Astrophysical Journal, 27 August 2014, p. 3; "Kepler-186 f", NASA Exoplanet Archive; Ross, "Earth, an Extraordinary Magnet for Life", Reasons to Believe, 2019-04-15; Staff, "Kepler 186f – A Planet in the Habitable Zone (video)", Hangout On-Air, 17 April 2014 (we also read that source) en.wikipedia.org
  8. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Burke, "Re-evaluating Small Long-period Confirmed Planets from Kepler", The Astronomical Journal, April 2019, p. 143; Burke, "Re-evaluating Small Long-period Confirmed Planets from Kepler", The Astronomical Journal, April 2019, p. 143; Robnik, "Reassessment of Kepler's habitable zone Earth-like exoplanets with data-driven null-signal templates", September 2019 (original not read by us) en.wikipedia.org
  9. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: Quintana, "Kepler 186f – First Earth-sized Planet Orbiting in Habitable Zone of Another Star", SETI Institute, 17 April 2014; Farmer, "A better than 50/50 chance Kepler-186f has technological life", Science 20, 18 April 2014; Kevvy, "The (Preliminary and Premature) Green Bank SERENDIP Fundraiser – Help SETI@Home Build a New (non-Arecibo) Receiver!", SETI@home, 20 March 2014; Siemion, "A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets", The Astrophysical Journal, 2013, p. 94 (orig en.wikipedia.org
  10. Wikipedia, "Kepler-186f" (CC BY-SA 4.0), which cites: "Kepler-186 f", NASA Exoplanet Archive; Fraser Cain, "How Old is the Sun?", Universe Today, 16 September 2008; Fraser Cain, "Temperature of the Sun", Universe Today, 15 September 2008 (we also read that source) en.wikipedia.org
  11. Johnson, "NASA's Kepler Discovers First Earth-Size Planet in The 'Habitable Zone' of Another Star", NASA, 17 April 2014. facts only, no text reused. nasa.gov
  12. "NASA Kepler telescope discovers planet believed to be most Earth-like yet found", The Guardian, 17 April 2014. facts only, no text reused. theguardian.com
  13. Ross, "Earth, an Extraordinary Magnet for Life", Reasons to Believe, 2019-04-15. facts only, no text reused. reasons.org

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Kepler-186f (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

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Sources

Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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