Kepler-90h#Habitability

Kepler-90h is a gas giant with no solid surface. Its equilibrium temperature is {{convert|292|K|C F}}. It is around 0.64 times as massive and around 1.01 times as large as Jupiter. This makes it very similar to Jupiter, in terms of mass and radius.

File:Kepler-90 MultiExoplanet System - 20171214.jpg

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

{{See also|Habitability of natural satellites}}

Kepler-90h resides in the circumstellar habitable zone of the parent star. The exoplanet, with a radius of 1.01 {{Jupiter radius}}, 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.

For a stable orbit the ratio between the moon's orbital period P_s around its primary and that of the primary around its star P_p 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.{{cite journal| last=Kipping| first=David| title=Transit timing effects due to an exomoon| journal=Monthly Notices of the Royal Astronomical Society| year=2009| volume=392| issue=1| pages=181–189| doi=10.1111/j.1365-2966.2008.13999.x| doi-access=free| bibcode = 2009MNRAS.392..181K |arxiv = 0810.2243}}{{cite journal| last1=Heller| first1=R.| title=Exomoon habitability constrained by energy flux and orbital stability| journal=Astronomy & Astrophysics| volume=545| year=2012| pages=L8| issn=0004-6361| doi=10.1051/0004-6361/201220003| arxiv = 1209.0050 |bibcode = 2012A&A...545L...8H | s2cid=118458061}} 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.{{cite web| url=http://www.skyandtelescope.com/resources/seti/3304591.html?showAll=y&c=y| publisher= SkyandTelescope.com| title=Habitable Moons:What does it take for a moon — or any world — to support life?| author=Andrew J. LePage| access-date=11 July 2011}} 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{{cite web| last=Glatzmaier| first=Gary A.| title=How Volcanoes Work – Volcano Climate Effects| url=http://www.geology.sdsu.edu/how_volcanoes_work/climate_effects.html| access-date=29 February 2012| archive-date=23 April 2011| archive-url=https://web.archive.org/web/20110423214804/http://www.geology.sdsu.edu/how_volcanoes_work/climate_effects.html| url-status=dead}}{{cite web| title=Solar System Exploration: Io| url=http://solarsystem.nasa.gov/planets/profile.cfm?Object=Io| archive-url=https://web.archive.org/web/20031216112404/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Io| url-status=dead| archive-date=16 December 2003| work=Solar System Exploration| publisher=NASA| access-date=29 February 2012}} and create a geodynamo effect which would give the satellite a strong magnetic field.{{cite web| last=Nave| first=R.| title=Magnetic Field of the Earth| url=http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html| access-date=29 February 2012}}

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 {{Earth mass|sym=y}}.{{cite web| url=http://www.xs4all.nl/~carlkop/habit.html|title=In Search Of Habitable Moons| publisher=Pennsylvania State University| access-date=11 July 2011}} 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 {{Earth mass|sym=y}}.

{{main|Kepler-90}}

The planet orbits a F-type star named Kepler-90, its host star. The star is 1.2 times as massive as the Sun and is 1.2 times as large as the Sun. It is estimated to be 2 billion years old, with a surface temperature of 6080 K. In comparison, the Sun is about 4.6 billion years old{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |publisher=Universe Today |access-date=19 February 2011}} and has a surface temperature of 5778 K.{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=15 September 2008 |publisher=Universe Today |access-date=19 February 2011}}

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 14.{{cite encyclopedia|url=https://exoplanet.eu/catalog/kepler_90_b--1440/|encyclopedia=Extrasolar Planets Encyclopaedia|title=Planet Kepler-90 b|access-date=26 April 2018}} It is too dim to be seen with the naked eye, which typically can only see objects with a magnitude around 6 or less.{{cite news|title=What's my naked-eye magnitude limit?|url=https://www.skyandtelescope.com/astronomy-resources/astronomy-questions-answers/naked-eye-magnitude-limit/|first=Roger W.|last=Sinnott|newspaper=Sky and Telescope|date=19 July 2006|access-date=17 April 2019}}

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 {{val|50,000}} 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.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). "[https://arxiv.org/abs/1310.5912 Planet The First Kepler Eight Planet Candidate System from the Kepler Archival Data]", Astrophysical Journal, p. 23.

File:Kepler-90 system rightward-PIA22193.jpg

• Kepler-47c
• HD 69830 d

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{{cite web|url=http://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=Kepler-90+h|title=Kepler-90 h|work=NASA Exoplanet Archive|access-date=15 July 2016}}

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Category:Exoplanets discovered by the Kepler space telescope

Category:Giant planets

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Category:Transiting exoplanets

Category:Giant planets in the habitable zone

Category:Kepler-90