TRAPPIST-1h

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TRAPPIST-1h
TRAPPIST-1h artist impression 2018.png
Artist's impression of TRAPPIST-1h
Discovery [1]
Discovered by Michaël Gillon et al.
Discovery site Spitzer Space Telescope
Discovery date22 February 2017
Transit
Orbital characteristics [2]
0.06189±0.00053  AU
Eccentricity 0.00567±0.00121 [3]
18.772866±0.000214  d
Inclination 89.805°±0.013°
338.92°±9.66° [3]
Star TRAPPIST-1 [4]
Physical characteristics [2]
0.755±0.014  R🜨
Mass 0.326±0.020  M🜨
Mean density
4.147+0.322
−0.302
  g/cm3
0.570±0.038 g
5.58±0.37  m/s2
Temperature Teq: 171.7±1.7  K (−101.5 °C; −150.6 °F) [5]

    TRAPPIST-1h, also designated as 2MASS J23062928-0502285 h, is an exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years (12.5 parsecs ) away from Earth in the constellation Aquarius. It was one of four new exoplanets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope. [6] [7] In the following years, more studies were able to refine its physical parameters.

    Contents

    The outermost known planet in its system, it is roughly one third the mass of Earth, and about 76% as large. Its relatively low density indicates that it is likely water-rich, like several other planets in the system. [8]

    Physical characteristics

    Mass, radius, and temperature

    TRAPPIST-1h has a radius of 0.755  R🜨 , a mass of 0.326  M🜨 , and about 57% Earth's surface gravity. [2] It was initially estimated to have a density of 3.97 g/cm3, similar to that of Mars. Given this density, about ≤5% of its mass may be water, likely in the form of a thick ice shell, [8] [9] since it only receives about 13% of the stellar flux that Earth does. It has an equilibrium temperature of 169 K (−104 °C; −155 °F), similar to that of Earth's south pole.

    Host star

    TRAPPIST-1h orbits the ultracool dwarf star TRAPPIST-1. It is 0.121 R and 0.089 M, with a temperature of 2,511 K and an age between 3 and 8 billion years. For comparison, the Sun has a temperature of 5,778 K and is about 4.5 billion years old. TRAPPIST-1 is also very dim, with about 0.0005 times the luminosity of the Sun. The star's apparent magnitude, or how bright it appears from Earth's perspective, is 18.8. Therefore, it is too dim to be seen with the naked eye.

    Orbit

    Despite it being the most distant known planet in its system, TRAPPIST-1h orbits its host star with an orbital period of 18.868 days and an orbital radius of about 0.0619 AU. This is even smaller than Mercury's orbit around the Sun (which is about 0.38 AU). [10]

    Stable liquid water

    Although TRAPPIST-1h's orbit falls near its star's frost line, it could harbor liquid water [11] [12] under an H2-rich atmosphere, either primordial or resulting from continuous outgassing combined with internal heating, [10] although existence of such atmosphere was strongly disfavored by observations in 2021 [13] and 2022. [14] If ice-covered, it could also potentially harbor a subsurface ocean by way of tidal heating, which could lead to cryovolcanism in the form of erupting geysers. [8] [9]

    See also

    Related Research Articles

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    <span class="mw-page-title-main">TRAPPIST-1</span> Ultra-cool red dwarf star in the constellation Aquarius

    TRAPPIST-1 is a cool red dwarf star with seven known exoplanets. It lies in the constellation Aquarius about 40.66 light-years away from Earth, and has a surface temperature of about 2,566 K. Its radius is slightly larger than Jupiter and it has a mass of about 9% of the Sun. It is estimated to be 7.6 billion years old, making it older than the Solar System. The discovery of the star was first published in 2000.

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    <span class="mw-page-title-main">TRAPPIST-1d</span> Small Venus-like exoplanet orbiting TRAPPIST-1

    TRAPPIST-1d is a small exoplanet, which orbits on the inner edge of the habitable zone of the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. The exoplanet was found by using the transit method. The first signs of the planet were announced in 2016, but it was not until the following years that more information concerning the probable nature of the planet was obtained. TRAPPIST-1d is the second-least massive planet of the system and is likely to have a compact hydrogen-poor atmosphere similar to Venus, Earth, or Mars. It receives just 4.3% more sunlight than Earth, placing it on the inner edge of the habitable zone. It has about <5% of its mass as a volatile layer, which could consist of atmosphere, oceans, and/or ice layers. A 2018 study by the University of Washington concluded that TRAPPIST-1d might be a Venus-like exoplanet with an uninhabitable atmosphere. The planet is an eyeball planet candidate.

    <span class="mw-page-title-main">TRAPPIST-1b</span> Rocky exoplanet orbiting TRAPPIST-1

    TRAPPIST-1b is a terrestrial, Earth-sized exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. The planet was detected using the transit method, where a planet dims the host star's light as it passes in front of it. It was first announced on May 2, 2016, and later studies were able to refine its physical parameters.

    <span class="mw-page-title-main">TRAPPIST-1c</span> Rocky exoplanet orbiting TRAPPIST-1

    TRAPPIST-1c, also designated as 2MASS J23062928-0502285 c, is a mainly rocky exoplanet orbiting around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years (12.5 parsecs) away from Earth in the constellation Aquarius. It is the third most massive and third largest planet of the system, with about 131% the mass and 110% the radius of Earth. Its density indicates a primarily rocky composition, and observations by the James Webb Space Telescope announced in 2023 suggests against a thick CO2 atmosphere, however this does not exclude a thick abiotic oxygen-dominated atmosphere as is hypothesized to be common around red dwarf stars.

    <span class="mw-page-title-main">Ultra-cool dwarf</span> Class-M stars with a temperature below 2,700 K

    An ultra-cool dwarf is a stellar or sub-stellar object that has an effective temperature lower than 2,700 K . This category of dwarf stars was introduced in 1997 by J. Davy Kirkpatrick, Todd J. Henry, and Michael J. Irwin. It originally included very low mass M-dwarf stars with spectral types of M7 but was later expanded to encompass stars ranging from the coldest known to brown dwarfs as cool as spectral type T6.5. Altogether, ultra-cool dwarfs represent about 15% of the astronomical objects in the stellar neighborhood of the Sun. One of the best known examples is TRAPPIST-1.

    <span class="mw-page-title-main">TRAPPIST-1f</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1f, also designated as 2MASS J23062928-0502285 f, is an exoplanet, likely rocky, orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. 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.

    <span class="mw-page-title-main">TRAPPIST-1g</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1g, also designated as 2MASS J23062928-0502285 g and K2-112 g, is an exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation Aquarius. It was one of four new exoplanets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope. The exoplanet is within the optimistic habitable zone of its host star. It 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.

    <span class="mw-page-title-main">TRAPPIST-1e</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1e, also designated as 2MASS J23062928-0502285 e, is a rocky, close-to-Earth-sized exoplanet orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. Astronomers used the transit method to find the exoplanet, a method that measures the dimming of a star when a planet crosses in front of it.

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    References

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