Kepler-90h

Kepler-90h
Exoplanet List of exoplanets

Comparison of the orbits of the Kepler-90 system to those of the inner Solar System.
Parent star
Star Kepler-90
Constellation Draco
Right ascension (α) 18h 57m 44.04s
Declination (δ) +49° 18′ 18.6″
Apparent magnitude (mV) 14[1]
Distance2545 ly
(780 pc)
Spectral type G0V
Mass (m) 1.2 (± 0.1)[2] M☉
Radius (r) 1.2 (± 0.1)[2] R☉
Temperature (T) 6080+260
−170[2] K
Metallicity [Fe/H] −0.12 (± 0.18)[2]
Age ~2 Gyr
Physical characteristics
Mass(m)≤1.2[2] MJ
Radius(r)1.01 (± 0.09)[2] RJ
Temperature (T) 292 K (19 °C; 66 °F)[3]
Orbital elements
Semi-major axis(a) 1.01 ± 0.11[1] AU
Eccentricity (e) 0.0 ≤ 0.001[1]
Orbital period(P) 331.60 ± 0.00037[1] d
Inclination (i) 89.6 ± 1.3[3]°
Discovery information
Discovery date November 12, 2013[1]
Discoverer(s) Kepler spacecraft
Discovery method Transit[3]
Discovery status Published
Other designations
KOI-351.01,[4] KOI-351 h, K00351.01, WISE J185744.03+491818.5 h, KIC 11442793 h, 2MASS J18574403+4918185 h
Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata
Exoplanet Archivedata
Open Exoplanet Cataloguedata

Kepler-90h (also known by its Kepler Object of Interest designation KOI-351.01) is an exoplanet orbiting within the habitable zone of the early G-type main sequence star Kepler-90, the outermost of seven such planets discovered by NASA's Kepler spacecraft. It is located about 2,545 light-years (780 parsecs, or nearly 2.4078×1016 km) from Earth in the constellation Draco. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.

Characteristics

Mass, radius and temperature

Kepler-90h is a gas giant, a planet that has a radius and mass around the same as that of the planets Jupiter and Saturn. It has a temperature of 292 K (19 °C; 66 °F), close to that of Earth. It has a mass around 1.2 MJ, and a radius less than or equal to around 1.01 RJ. This makes it very similar to Jupiter, in terms of mass and radius.

Host star

The planet orbits a (G-type) star named Kepler-90. The star has a mass of 1.2 M☉ and a radius 1.2 R☉. It has a surface temperatures of 6080 K and has an estimated age of around 2 billion years. In comparison, the Sun is about 4.6 billion years old[5] and has a surface temperature of 5778 K.[6]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 14. It is too dim to be seen with the naked eye.

Orbital statistics

Kepler-90h orbits its host star about every 331.6 days at a distance of 1.01 AU, very similar to Earth's orbital distance from the Sun (which is 1 AU).

Habitability

Kepler-90h resides in the circumstellar habitable zone of the parent star. The exoplanet, with a radius of 1.01 RJ, is too large to be rocky, and because of this the planet itself may not be habitable. Hypothetically, large enough moons, with a sufficient atmosphere and pressure, may be able to support liquid water and potentially life. However, such moons do not usually form around planets, they would likely have to be captured from afar; e.g, a protoplanet running astray.

For a stable orbit the ratio between the moon's orbital period Ps around its primary and that of the primary around its star Pp must be < 1/9, e.g. if a planet takes 90 days to orbit its star, the maximum stable orbit for a moon of that planet is less than 10 days.[7][8] Simulations suggest that a moon with an orbital period less than about 45 to 60 days will remain safely bound to a massive giant planet or brown dwarf that orbits 1 AU from a Sun-like star.[9] In the case of Kepler-90h, this would be practically the same to have a stable orbit.

Tidal effects could also allow the moon to sustain plate tectonics, which would cause volcanic activity to regulate the moon's temperature[10][11] and create a geodynamo effect which would give the satellite a strong magnetic field.[12]

To support an Earth-like atmosphere for about 4.6 billion years (the age of the Earth), the moon would have to have a Mars-like density and at least a mass of 0.07 M⊕.[13] One way to decrease loss from sputtering is for the moon to have a strong magnetic field that can deflect stellar wind and radiation belts. NASA's Galileo's measurements hints large moons can have magnetic fields; it found that Jupiter's moon Ganymede has its own magnetosphere, even though its mass is only 0.025 M⊕.[9]

Discovery

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-90; 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. Observations for the potential exoplanet candidates took place between 13 May 2009 and 17 March 2012. After observing the respective transits, which for Kepler-90h occurred roughly every 331 days (its orbital period), it was eventually concluded that a planetary body was responsible for the periodic 331-day transits. The discovery, was announced on November 12, 2013.[4]

See also

References

  1. 1 2 3 4 5 "TEPcat: Kepler-90h". www.astro.keele.ac.uk. December 31, 2013. Retrieved January 3, 2013.
  2. 1 2 3 4 5 6 "Kepler-90 h". NASA Exoplanet Archive. Retrieved July 15, 2016.
  3. 1 2 3 "Planet Kepler-90 h". exoplanet.eu. Retrieved January 3, 2014.
  4. 1 2 Schmitt, Joseph R.; Wang, Ji; Fischer, Debra A.; Jek, Kian J.; Moriarty, John C.; Boyajian, Tabetha S.; Schwamb, Megan E.; Lintott, Chris; Smith, Arfon M.; Parrish, Michael; Schawinski, Kevin; Lynn, Stuart; Simpson, Robert; Omohundro, Mark; Winarski, Troy; Goodman, Samuel J.; Jebson, Tony; Lacourse, Daryll (2013). "Planet Hunters VI: The First Kepler Seven Planet Candidate System and 13 Other Planet Candidates from the Kepler Archival Data", Astrophysical Journal, p. 23.
  5. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  6. ↑ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  7. ↑ Kipping, David (2009). "Transit timing effects due to an exomoon". Monthly Notices of the Royal Astronomical Society. 392: 181–189. arXiv:0810.2243Freely accessible. Bibcode:2009MNRAS.392..181K. doi:10.1111/j.1365-2966.2008.13999.x. Retrieved 22 February 2012.
  8. ↑ Heller, R. (2012). "Exomoon habitability constrained by energy flux and orbital stability". Astronomy & Astrophysics. 545: L8. arXiv:1209.0050Freely accessible. Bibcode:2012A&A...545L...8H. doi:10.1051/0004-6361/201220003. ISSN 0004-6361.
  9. 1 2 Andrew J. LePage. "Habitable Moons:What does it take for a moon — or any world — to support life?". SkyandTelescope.com. Retrieved 2011-07-11.
  10. ↑ Glatzmaier, Gary A. "How Volcanoes Work – Volcano Climate Effects". Retrieved 29 February 2012.
  11. ↑ "Solar System Exploration: Io". Solar System Exploration. NASA. Retrieved 29 February 2012.
  12. ↑ Nave, R. "Magnetic Field of the Earth". Retrieved 29 February 2012.
  13. ↑ "In Search Of Habitable Moons". Pennsylvania State University. Retrieved 2011-07-11.

Coordinates: 18h 57m 44.04s, +49° 18′ 18.6″

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