Kepler-452

Kepler-452 is a G-type main-sequence star located about 1,402 light-years away from Earth[1] in the Cygnus constellation.[3] Although similar in temperature to the Sun, it is 20% brighter, 3.7% more massive and 11% larger.[4][5] Alongside this, the star is approximately six billion years old and possesses a high metallicity.[6] Thus, Kepler-452 can be considered a solar twin, although it could considered to be a solar analog due to its age.[lower-alpha 1]

Kepler-452

Artist's impression of the Kepler-452 and Kepler-186 systems compared to the inner Solar System, with their respective habitable zones shown.
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension  19h 44m 00.8861s[1]
Declination +44° 16′ 39.1704″[1]
Apparent magnitude (V) 13.426[2]
Characteristics
Evolutionary stage Main sequence
Spectral type G2V
Astrometry
Proper motion (μ) RA: 9.974±0.029[1] mas/yr
Dec.: 9.012±0.042[1] mas/yr
Parallax (π)1.7838 ± 0.0169[1] mas
Distance1,830 ± 20 ly
(561 ± 5 pc)
Details
Mass1.037+0.054
−0.047 M☉
Radius1.11+0.15
−0.09 R☉
Luminosity1.2 L☉
Surface gravity (log g)4.32 ± 0.09 cgs
Temperature5757 ± 85 K
Metallicity [Fe/H]0.21 ± 0.09 dex
Age6 ± 2 Gyr
Other designations
KOI-7016, KIC-8311864, 2MASS 19440088+4416392, GSC 3148-814
Database references
Exoplanet Archivedata

Nomenclature and history
The Kepler Space Telescope search volume, in the context of the Milky Way Galaxy.

Prior to Kepler observation, Kepler-452 had the 2MASS catalogue number 2MASS 19440088+4416392. In the Kepler Input Catalog, it has the designation of KIC 8311864 When it was found to have a transiting planet candidate, it was given the Kepler object of interest number of KOI-7016.

Planetary candidates were detected around the star by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness of stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomena can also be responsible which is why the term "planetary candidate" is used.[9]

Following the acceptance of the discovery paper, the Kepler team referred to the star as Kepler-452, which is the normal procedure for naming exoplanets discovered by the spacecraft.[10][6] Hence, this is the name usually used by the public to refer to the star and its planet.

Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01", ".02", and so on, after the star's name, in the order of discovery.[2] If planet candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest.[2] Following these rules, there was only one candidate planet detected, with an orbital period of 384.843 days. The name Kepler-452 derives directly from the fact that the star is the catalogued 452nd star discovered by Kepler to have confirmed planets.

The designation b, derives from the order of discovery. The designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet.[11] In the case of Kepler-452, there was only one planet, so only the letter b is used.

Stellar characteristics

Kepler-452 is a G-type star that is approximately 104% the mass of and 111% the radius of the Sun. It has a temperature of 5757 K and is roughly 6 billion years old. In comparison, the Sun is about 4.6 billion years old[12] and has a temperature of 5778 K.[13]

The star is metal-rich, with a metallicity (Fe/H) of about 0.21, or about 162% of the amount of iron and other heavier metals found in the Sun.[6] The star's luminosity is somewhat normal for a star like Kepler-452, with a luminosity of around 120% of that of the solar luminosity.

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 13.426. Therefore, it is too dim to be seen with the naked eye.

Planetary system

The star hosts one confirmed exoplanet, Kepler-452b, discovered in July 2015 by the Kepler spacecraft. This planet is mostly known for its characteristics similar to Earth, most notably its size, orbit and stellar flux. It is the first potentially rocky super-Earth[14] planet discovered orbiting within the habitable zone and the abiogenesis zone of a star very similar to the Sun.[4][15] It may even have a surface temperature similar to that of Earth (the planet has an equilibrium temperature of approximately 265 K (−8 °C; 17 °F) (Earth's equilibrium temperature is only 10 K cooler than this). However, its star is 6 billion years old (roughly 1.5 billion years older than the Sun). Due to this, Kepler-452b is receiving roughly 10% more stellar radiation than the Earth does today. If Kepler-452b is a rocky planet, it may be subject to a runaway greenhouse effect. However, because of its mass (estimated to be about 5 M⊕), it may be able to prevent succumbing to the runaway greenhouse for a limited amount of time (at most about 500 million years). Nevertheless, the planet is one of the most Earth-like planets discovered so far by the Kepler team.

The Kepler-452 planetary system[16]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 5 ± 2[17] M⊕ 1.046+0.019
−0.015		 384.843+0.007
−0.012		 — 89.806+0.134
−0.049°		 1.5+0.32
−0.22 R⊕

Sun comparison

This table compares the Sun to Kepler-452.

Identifier J2000 Coordinates Distance
(ly)		 Stellar
Class		 Temperature
(K)		 Metallicity
(dex)		 Age
(Gyr)		 Notes
Right ascension Declination
Sun — — 0.00 G2V 5,778 +0.00 4.6 [8]
Kepler-452 [18]  19h 44m 00.89s +44° 16′ 39.2″ 1,400 G2V 5,757 +0.21 6.0 [19]

Footnotes
  1. An exact solar twin would be a G2V star with a 5778 K temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation.[7][8]
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gollark: It does, the S is silent and unwritten except to mute speakers of old Icelandic.
gollark: Well, it is the superior PACkage MANager.
gollark: Though make sure to install the kernel and a text editor and networking drivers as they are no longer in `base`.
gollark: And `pacman` is a cool package manager.

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. "Kepler Input Catalog search result". Space Telescope Science Institute. Retrieved 25 July 2015.
  3. Witze, Alexandra (23 July 2015). "NASA spies Earth-sized exoplanet orbiting Sun-like star". Nature. Retrieved 23 July 2015.
  4. Chou, Felicia; Johnson, Michelle (23 July 2015). "NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth" (Press release). NASA. Retrieved 23 July 2015.
  5. Rincon, Paul (23 July 2015). "'Earth 2.0' found in Nasa Kepler telescope haul". BBC. Retrieved 23 July 2015.
  6. Jenkins, Jon M.; Twicken, Joseph D.; Batalha, Natalie M.; Caldwell, Douglas A.; Cochran, William D.; Endl, Michael; et al. (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. Institute of Physics. 105 (2): 56. arXiv:1507.06723. Bibcode:2015AJ....150...56J. doi:10.1088/0004-6256/150/2/56.
  7. "Solar Variability and Terrestrial Climate - NASA Science". Retrieved 8 January 2013.
  8. Williams, David R. (2004). "Sun Fact Sheet". NASA. Retrieved 23 June 2009.
  9. Morton, Timothy; Johnson, John (23 August 2011). "On the Low False Positive Probabilities of Kepler Planet Candidates". The Astrophysical Journal. 738 (2): 170. arXiv:1101.5630. Bibcode:2011ApJ...738..170M. doi:10.1088/0004-637X/738/2/170.
  10. NASA (27 January 2014). "Kepler – Discoveries – Summary Table". NASA. Retrieved 1 March 2014.
  11. Hessman, Frederic V.; Dhillon, Vikram S.; Winget, Donald E.; Schreiber, Matthias R.; Horne, Keith; Marsh, Thomas R.; Guenther, Eike W.; Schwope, Axel D.; Heber, Ulrich (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  12. Williams, Matt (9 May 2016). "Life Cycle of the Sun". Universe Today. Retrieved 17 August 2016.
  13. Cain, Fraser (23 December 2015). "What Color is the Sun?". Universe Today. Retrieved 17 August 2016.
  14. "The Habitable Exoplanets Catalog – Planetary Habitability Laboratory @ UPR Arecibo". upr.edu.
  15. "Super-earth 'most likely' candidate for hosting alien life". Sky News. Retrieved 3 August 2018.
  16. "NASA Exoplanet Archive – Confirmed Planet Overview – Kepler-452b". NASA Exoplanet Archive. 2015. Retrieved 23 July 2015.
  17. "NASA's Kepler Mission Discovers Bigger, Older Cousin to Earth". National Aeronautics and Space Administration. 23 July 2015. Retrieved 10 June 2016.
  18. Kepler-452 at SIMBAD - Ids - Bibliography - Image.
  19. "Planet Kepler-452 b (sic)". Retrieved 6 July 2016.
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