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Kepler-452b

Coordinates: Sky map 19h 44m 00.89s, +44° 16′ 39.2″
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Kepler-452b is an exoplanet orbiting the G-class star Kepler-452. It was identified by the Kepler space telescope and its discovery was publicly announced by NASA on 23 July 2015.[1] It is the first near-Earth-size planet discovered orbiting within the habitable zone of a star very similar to the Sun.[2] It is the second-most Earth-like exoplanet known to date, after Kepler-438b, although it is not known if Kepler-452b is rocky or a small gas planet.[3] However based on its density, it is probably a rocky planet.

The star is 1,400 light-years away from the Solar System; at the speed of New Horizons it would take about 25.8 million years to get there.[4]

Properties

The planet takes 385 days to orbit its star.[5] It is older and bigger than Earth, but lies within the conservative habitable zone of its parent star.[6][7]

It has a probable mass five times that of Earth, and its surface gravity is twice Earth's, though calculations of mass for exoplanets are only rough estimates.[6] If it is a terrestrial planet, it is most likely a super-Earth with many active volcanoes due to its higher mass and density. The clouds on the planet would be thick and misty, covering much of the surface as viewed from space. Kepler-452 would look almost identical to the Sun as viewed from the surface.[8]

It is not clear if Kepler-452b offers habitable environments. It orbits a G2V-type star, like the Sun, with nearly the same temperature and mass. However, the star is six billion years old, making it 1.5 billion years older than the Sun. At this point in its star's evolution, Kepler-452b is receiving ten percent more energy from its parent star than Earth is currently receiving from the Sun. If Kepler-452b is a rocky planet, it would be subject to, or on the verge of, a runaway greenhouse effect.[9]

Comparison of Kepler-452b to Solar terrestrial planets
Name ESI SPH HZD HZC HZA pClass hClass Distance (ly) Status Year of
discovery
Earth Template:HabPlanetScore warm terran mesoplanet — — —
Kepler-438b Template:HabPlanetScore warm terran mesoplanet 470 Confirmed 2015
Kepler-452b Template:HabPlanetScore warm superterran mesoplanet 1,400 confirmed 2015
Mars Template:HabPlanetScore warm subterran hypopsychroplanet 0 non-exoplanet prehistoric
Mercury Template:HabPlanetScore hot mercurian non-habitable 0 non-exoplanet prehistoric
Venus Template:HabPlanetScore warm terran hyperthermoplanet 0 non-exoplanet prehistoric

Key

The planets listed above are evaluated on seven different criteria:

  • Earth Similarity Index (ESI)—Similarity to Earth on a scale from 0 to 1, with 1 being the most Earth-like. ESI depends on the planet's radius, density, escape velocity, and surface temperature.
  • Standard Primary Habitability (SPH)—Suitability for vegetation on a scale from 0 to 1, with 1 being best-suited for growth. SPH depends on surface temperature (and relative humidity if known).
  • Habitable Zone Distance (HZD)—Distance from the center of the star's habitable zone, scaled so that –1 represents the inner edge of the zone, and +1 represents the outer edge. HZD depends on the star's luminosity and temperature and the size of the planet's orbit. Note that even though many planets have an HZD value similar to Venus (–0.93), including Kepler-438b, the HZD is not used to rule on whether a planet has suffered a runaway greenhouse effect or not, and therefore, Kepler-438b is currently assumed to be a mesoplanet rather than a hyperthermoplanet.
  • Habitable Zone Composition (HZC)—Measure of bulk composition, where values close to zero are likely iron–rock–water mixtures. Values below –1 represent bodies likely composed mainly of iron, and values greater than +1 represent bodies likely composed mainly of gas. HZC depends on the planet's mass and radius.
  • Habitable Zone Atmosphere (HZA)—Potential for the planet to hold a habitable atmosphere, where values below –1 represent bodies likely with little or no atmosphere, and values above +1 represent bodies likely with thick hydrogen atmospheres (e.g. gas giants). Values between –1 and +1 are more likely to have atmospheres suitable for life, though zero is not necessarily ideal. HZA depends on the planet's mass, radius, orbit size, and the star's luminosity.
  • Planetary Class (pClass)—Classifies objects based on thermal zone (hot, warm, or cold, where warm is in the habitable zone) and mass (asteroidan, mercurian, subterran, terran, superterran, neptunian, and jovian).
  • Habitable Class (hClass)—Classifies habitable planets based on temperature: hypopsychroplanets (hP) = very cold (< −50 °C); psychroplanets (P) = cold; mesoplanets (M) = medium-temperature (0–50 °C; not to be confused with the other definition of mesoplanets); thermoplanets (T) = hot; hyperthermoplanets (hT) = very hot (> 100 °C). Mesoplanets would be ideal for complex life, whereas class hP or hT would only support extremophilic life. Non-habitable planets are simply given the class NH.
  • A diagram of the orbit of Kepler-452b within the Kepler-452 system, as compared to the inner Solar System and Kepler-186 system, and their respective projected habitable zones.
    A diagram of the orbit of Kepler-452b within the Kepler-452 system, as compared to the inner Solar System and Kepler-186 system, and their respective projected habitable zones.
  • This artist's concept compares Earth (left) to Kepler-452b, which is about 60 percent larger in diameter.
    This artist's concept compares Earth (left) to Kepler-452b, which is about 60 percent larger in diameter.
  • Comparison of small planets found by Kepler in the habitable zone of their host stars.
    Comparison of small planets found by Kepler in the habitable zone of their host stars.
  • Comparison of Kepler-452b and related exoplanets with Earth
    Comparison of Kepler-452b and related exoplanets with Earth

See also

Wikimedia Commons has media related to Kepler-452b.

References

  1. ^ Jenkins, Jon M.; Twicken, Joseph D.; Batalha, Natalie M.; Caldwell, Douglas A.; Cochran, William D.; Endl, Michael; Latham, David W.; Esquerdo, Gilbert A.; Seader, Shawn; Bieryla, Allyson; Petigura, Erik; Ciardi, David R.; Marcy, Geoffrey W.; Isaacson, Howard; Huber, Daniel; Rowe, Jason F.; Torres, Guillermo; Bryson, Stephen T.; Buchhave, Lars; Ramirez, Ivan; Wolfgang, Angie; Li, Jie; Campbell, Jennifer R.; Tenenbaum, Peter; Sanderfer, Dwight; Henze, Christopher E.; Catanzarite, Joseph H.; Gilliland, Ronald L.; Borucki, William J. (23 July 2015). "Discovery and Validation of Kepler-452b: A 1.6 R⨁ Super Earth Exoplanet in the Habitable Zone of a G2 Star". The Astronomical Journal. 150 (2): 56. doi:10.1088/0004-6256/150/2/56. ISSN 1538-3881. Retrieved 24 July 2015.
  2. ^ Chou, Felicia; Johnson, Michelle (23 July 2015). "NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth" (Press release). NASA. Retrieved 23 July 2015.
  3. ^ Rincon, Paul (23 July 2015). "'Earth 2.0' found in Nasa Kepler telescope haul". BBC News. Retrieved 24 July 2015.
  4. ^ "NASA telescope discovers Earth-like planet in star's 'habitable zone". BNO News. 23 July 2015. Retrieved 23 July 2015.
  5. ^ Overbye, Dennis (23 July 2015). "Kepler Data Reveals What Might Be Best 'Goldilocks' Planet Yet". The New York Times. Retrieved 23 July 2015.
  6. ^ a b Feltman, Rachel (23 July 2015). "Scientists discover 12 new potential Earth-like planets". The Washington Post. Retrieved 23 July 2015.
  7. ^ Witze, Alexandra (23 July 2015). "NASA spies Earth-sized exoplanet orbiting Sun-like star". Nature. Retrieved 23 July 2015.
  8. ^ NASA Kepler press conference. 23 July 2015.
  9. ^ Lugmayr, Luigi (23 July 2015). "Kepler-452b details unveiled". I4U News. Retrieved 23 July 2015.
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