Discovery | |
---|---|
Discovered by | Kepler spacecraft |
Discovery date | November 12, 2013 [1] |
Transit [2] | |
Orbital characteristics | |
1.01 ± 0.11 AU (151,000,000 ± 16,000,000 km) [1] | |
Eccentricity | 0.0 ≤ 0.001 [1] |
331.60 ± 0.00037 [1] d | |
Inclination | 89.6 ± 1.3 [2] |
Star | Kepler-90 |
Physical characteristics | |
Mean radius | 1.01 (± 0.09) [3] RJ |
Mass | 0.639±0.016 [4] MJ |
Temperature | 292 K (19 °C; 66 °F) [2] |
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 eight such planets discovered by NASA's Kepler spacecraft. It is located about 2,840 light-years (870 parsecs), 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.
Kepler-90h is a gas giant with no solid surface. Its equilibrium temperature is 292 K (19 °C; 66 °F). [3] It is around 0.64 times as massive and around 1.01 times as large as Jupiter. [3] This makes it very similar to Jupiter, in terms of mass and radius. [3]
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). [3]
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.
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. [5] [6] 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. [7] 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 [8] [9] and create a geodynamo effect which would give the satellite a strong magnetic field. [10]
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 MEarth. [11] 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 MEarth. [7]
The planet orbits a G-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 [12] and has a surface temperature of 5778 K. [13]
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 14. [14] It is too dim to be seen with the naked eye, which typically can only see objects with a magnitude around 6 or less. [15]
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. [16]
Gliese 876 b is an exoplanet orbiting the red dwarf Gliese 876. It completes one orbit in approximately 61 days. Discovered in June 1998, Gliese 876 b was the first planet to be discovered orbiting a red dwarf.
HD 69830 d is an exoplanet likely orbiting within the habitable zone of the star HD 69830, the outermost of three such planets discovered in the system. It is located approximately 40.7 light-years (12.49 parsecs, or 3.8505×1014 km) from Earth in the constellation of Puppis. The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star.
The habitability of natural satellites describes the study of a moon's potential to provide habitats for life, though is not an indicator that it harbors it. Natural satellites are expected to outnumber planets by a large margin and the study is therefore important to astrobiology and the search for extraterrestrial life. There are, nevertheless, significant environmental variables specific to moons.
Kepler-16b is an exoplanet. It is a Saturn-mass planet consisting of half gas and half rock and ice, and it orbits a binary star, Kepler-16, with a period of 229 days. "[It] is the first confirmed, unambiguous example of a circumbinary planet – a planet orbiting not one, but two stars," said Josh Carter of the Center for Astrophysics | Harvard & Smithsonian, one of the discovery team.
Kepler-22b is an exoplanet orbiting within the habitable zone of the Sun-like star Kepler-22. It is located about 640 light-years from Earth in the constellation of Cygnus. It was discovered by NASA's Kepler Space Telescope in December 2011 and was the first known transiting planet to orbit within the habitable zone of a Sun-like star, where liquid water could exist on the planet's surface. Kepler-22 is too dim to be seen with the naked eye.
Kepler-47c is an exoplanet orbiting the binary star system Kepler-47, the outermost of three such planets discovered by NASA's Kepler spacecraft. The system, also involving two other exoplanets, is located about 3,400 light-years away.
Kepler-69c is a confirmed super-Earth extrasolar planet, likely rocky, orbiting the Sun-like star Kepler-69, the outermore of two such planets discovered by NASA's Kepler spacecraft. It is located about 2,430 light-years from Earth.
Kepler-62e is a super-Earth exoplanet discovered orbiting within the habitable zone of Kepler-62, the second outermost of five such planets discovered by NASA's Kepler spacecraft. Kepler-62e is located about 990 light-years from Earth in the constellation of Lyra. The exoplanet was found using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-62e may be a terrestrial or ocean-covered planet; it lies in the inner part of its host star's habitable zone.
Kepler-62c is an approximately Mars-sized exoplanet discovered in orbit around the star Kepler-62, the second innermost of five discovered by NASA's Kepler spacecraft around Kepler-62. At the time of discovery it was the second-smallest exoplanet discovered and confirmed by the Kepler spacecraft, after Kepler-37b. It was found using the transit method, in which the dimming that a planet causes as it crosses in front of its star is measured. Its stellar flux is 25 ± 3 times Earth's. It is similar to Mercury.
Kepler-62d is the third innermost and the largest exoplanet discovered orbiting the star Kepler-62, with a size roughly twice the diameter of Earth. It was found using the transit method, in which the dimming that a planet causes as it crosses in front of its star is measured. Its stellar flux is 15 ± 2 times Earth's. Due to its closer orbit to its star, it is a super-Venus or, if it has a volatile composition, a hot Neptune, with an estimated equilibrium temperature of 510 K, too hot to sustain life on its surface.
Kepler-62b is the innermost and the second smallest discovered exoplanet orbiting the star Kepler-62, with a diameter roughly 30% larger than Earth. It was found using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. It is likely to have an equilibrium temperature slightly higher than the surface temperature of Venus, high enough to melt some types of metal. Its stellar flux is 70 ± 9 times Earth's.
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Kepler-452 is a G-type main-sequence star located about 1,800 light-years away from Earth in the Cygnus constellation. Although similar in temperature to the Sun, it is 20% brighter, 3.7% more massive and 11% larger. Alongside this, the star is approximately six billion years old and possesses a high metallicity. Thus, Kepler-452 can be considered a solar twin, although it could be considered a solar analog due to its age.
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