TRAPPIST-1g

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TRAPPIST-1g
TRAPPIST-1g artist impression 2018.png
Artist's impression of TRAPPIST-1g. (February 2018)
Discovery [1]
Discovered by Michaël Gillon et al.
Discovery site Spitzer Space Telescope
Discovery date22 February 2017
Transit
Orbital characteristics [2]
0.04683±0.00040  AU
Eccentricity 0.00208±0.00058 [3]
12.352446±0.000054  d
Inclination 89.742°±0.012°
191.34°±13.83° [3]
Star TRAPPIST-1 [4]
Physical characteristics [2]
Mean radius
1.129+0.015
−0.013  R🜨
Mass 1.321±0.038  M🜨
Mean density
5.042+0.136
−0.158  g/cm3
1.035±0.026 g
10.15±0.25  m/s2
Temperature Teq: 197.3±1.9  K (−75.8 °C; −104.5 °F) [5]

    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 (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] The exoplanet is within the optimistic habitable zone of its host star. [7] 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.

    Contents

    The second most distant known planet in its system, TRAPPIST-1g is a planet somewhat larger than Earth and with a similar density, meaning it is likely a rocky planet. [2]

    Physical characteristics

    Mass, radius, and temperature

    TRAPPIST-1g has a radius of 1.129  R🜨 and a mass of 1.321  M🜨 , with a density only slightly less than Earth's, [2] though initial estimates suggested its density was only 4.186 g/cm3, about 76% of Earth's. [3] Based on mass-radius calculations and its distant location relative to its host star (0.047 AU) and the fact that the planet only receives 25.2% of the stellar flux that Earth does, the planet is likely covered by a thick ice envelope if an atmosphere does not exist. [8]

    Atmosphere

    TRAPPIST-1g could have a global water ocean or an exceptionally thick steam atmosphere. [3] According to a simulation of magma ocean-atmosphere interaction, TRAPPIST-1g is likely to retain a large fraction of primordial steam atmosphere during the initial stages of evolution, and therefore today is likely to possess a thick ocean covered by atmosphere containing hundreds of bars of abiotic oxygen. [9]

    On 31 August 2017, astronomers at the Hubble Space Telescope reported the first evidence of possible water content on the TRAPPIST-1 exoplanets. [10] [11] [12]

    Host star

    The planet orbits an (M-type) ultracool dwarf star named TRAPPIST-1. The star has a mass of 0.08 M☉ and a radius of 0.11 R☉. It has a temperature of 2550 K. The age of the star is about 7.6±2.2 billion years old. [13] In comparison, the Sun is 4.6 billion years old and has a temperature of 5778 K. The star is metal-rich, with a metallicity ([Fe/H]) of 0.04, or 109% the solar amount. This is particularly odd as such low-mass stars near the boundary between brown dwarfs and hydrogen-fusing stars should be expected to have considerably less metal content than the Sun. Its luminosity (L☉) is 0.05% of that of the Sun.

    The star's apparent magnitude, or how bright it appears from Earth's perspective, is 18.8, too dim to be seen with the naked eye.

    Orbit

    TRAPPIST-1g orbits its host star with an orbital period of about 12.354 days and an orbital radius of about 0.0451 times that of Earth's (compared to the distance of Mercury from the Sun, which is about 0.38 AU). This is in the outer limit of TRAPPIST-1's theoretical habitable zone. The orbit of TRAPPIST-1g has an eccentricity of 0.00208, [3] much lower than that of Earth and the lowest in its system. Its orbit varies by only about 41,000 kilometers (compared to about 5 million km for Earth), meaning the planet's climate is likely very stable. It is in a 3:2 orbital resonance with TRAPPIST-1h and a 3:4 resonance with TRAPPIST-1f.

    See also

    Related Research Articles

    <span class="mw-page-title-main">Transit-timing variation</span> Exoplanet detection method using transit timing variations

    Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small as that of Earth. In tightly packed planetary systems, the gravitational pull of the planets among themselves causes one planet to accelerate and another planet to decelerate along its orbit. The acceleration causes the orbital period of each planet to change. Detecting this effect by measuring the change is known as transit-timing variations. "Timing variation" asks whether the transit occurs with strict periodicity or if there's a variation.

    <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.

    <span class="mw-page-title-main">SPECULOOS</span> Astronomical observatory

    SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) is a project consisting of SPECULOOS Southern Observatory (SSO) at the Paranal Observatory in Chile and SPECULOOS Northern Observatory (SNO) at the Teide Observatory in Tenerife.

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

    TRAPPIST-1d, also designated as 2MASS J23062928-0502285 d, 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, in which the dimming effect that a planet causes as it crosses in front of its star is measured. The first signs of the planet were announced in 2016, but it wasn't 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, also designated as 2MASS J23062928-0502285 b, is a mainly rocky 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 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-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.

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

    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 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. In the following years, more studies were able to refine its physical parameters.

    WASP-121, also known as CD-38 3220, is a magnitude 10.4 star located approximately 858 light-years away in the constellation Puppis. WASP-121 has a mass and radius similar to the Sun's. It hosts one known exoplanet.

    <span class="mw-page-title-main">Ross 128 b</span> Confirmed terrestrial exoplanet orbiting Ross 128

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    K2-315b is an exoplanet located 185.3 light years away from Earth in the southern zodiac constellation Libra. It orbits the red dwarf K2-315.

    WASP-72 is the primary of a binary star system. It is an F7 class dwarf star, with an internal structure just on the verge of the Kraft break. It is orbited by a planet WASP-72b. The age of WASP-72 is younger than the Sun at 3.55±0.82 billion years.

    WASP-80 is a K-type main-sequence star about 162 light-years away from Earth. The star's age is much younger than the Sun's at 1.352±0.222 billion years. WASP-80 could be similar to the Sun in concentration of heavy elements, although this measurement is highly uncertain.

    WASP-103b is a gaseous exoplanet, more specifically a hot Jupiter, located in the Hercules constellation orbiting the star WASP-103. It has an oval shape, similar to that of a rugby ball, thanks to the force of gravity exerted by its star. It is the first exoplanet to have a deformation detected.

    References

    1. ↑ Gillon, M.; Triaud, A. H. M. J.; Demory, B.-O.; Jehin, E.; Agol, E.; Deck, K. M.; Lederer, S. M.; De Wit, J.; Burdanov, A.; Ingalls, J. G.; Bolmont, E.; Leconte, J.; Raymond, S. N.; Selsis, F.; Turbet, M.; Barkaoui, K.; Burgasser, A.; Burleigh, M. R.; Carey, S. J.; Chaushev, A.; Copperwheat, C. M.; Delrez, L.; Fernandes, C. S.; Holdsworth, D. L.; Kotze, E. J.; Van Grootel, V.; Almleaky, Y.; Benkhaldoun, Z.; Magain, P.; Queloz, D. (2017). "Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1" (PDF). Nature. 542 (7642): 456–460. arXiv: 1703.01424 . Bibcode:2017Natur.542..456G. doi:10.1038/nature21360. PMC   5330437 . PMID   28230125.
    2. 1 2 3 4 Agol, Eric; Dorn, Caroline; Grimm, Simon L.; Turbet, Martin; et al. (1 February 2021). "Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides". The Planetary Science Journal. 2 (1): 1. arXiv: 2010.01074 . Bibcode:2021PSJ.....2....1A. doi: 10.3847/psj/abd022 . S2CID   222125312.
    3. 1 2 3 4 5 Grimm, Simon L.; Demory, Brice-Olivier; Gillon, Michael; Dorn, Caroline; Agol, Eric; Burdanov, Artem; Delrez, Laetitia; Sestovic, Marko; Triaud, Amaury H.M.J.; Turbet, Martin; Bolmont, Emeline; Caldas, Anthony; de Wit, Julien; Jehin, Emmanuel; Leconte, Jeremy; Raymond, Sean N.; Van Grootel, Valerie; Burgasser, Adam J.; Carey, Sean; Fabrycky, Daniel; Heng, Kevin; Hernandez, David M.; Ingalls, James G.; Lederer, Susan; Selsis, Franck; Queloz, Didier (2018). "The nature of the TRAPPIST-1 exoplanets". Astronomy & Astrophysics. 613: A68. arXiv: 1802.01377 . Bibcode:2018A&A...613A..68G. doi:10.1051/0004-6361/201732233. S2CID   3441829.
    4. ↑ Van Grootel, Valerie; Fernandes, Catarina S.; Gillon, Michaël; Jehin, Emmanuel; Scuflaire, Richard; et al. (2018). "Stellar parameters for TRAPPIST-1". The Astrophysical Journal. 853 (1): 30. arXiv: 1712.01911 . Bibcode:2018ApJ...853...30V. doi: 10.3847/1538-4357/aaa023 . S2CID   54034373.
    5. ↑ Ducrot, E.; Gillon, M.; Delrez, L.; Agol, E.; et al. (1 August 2020). "TRAPPIST-1: Global results of the Spitzer Exploration Science Program Red Worlds". Astronomy & Astrophysics. 640: A112. arXiv: 2006.13826 . Bibcode:2020A&A...640A.112D. doi:10.1051/0004-6361/201937392. ISSN   0004-6361. S2CID   220041987.
    6. ↑ "Temperate Earth-Sized Planets Found in Extraordinarily Rich Planetary System TRAPPIST-1". SpaceRef. 22 February 2017. Retrieved 11 February 2017.
    7. ↑ "NASA telescope reveals largest batch of Earth-size, habitable-zone planets around single star". Exoplanet Exploration: Planets Beyond our Solar System (Press release). Retrieved 22 February 2017.
    8. ↑ Quick, Lynnae C.; Roberge, Aki; Tovar Mendoza, Guadalupe; Quintana, Elisa V.; Youngblood, Allison A. (4 October 2023). "Prospects for Cryovolcanic Activity on Cold Ocean Planets". The Astrophysical Journal. 956 (29): 29. Bibcode:2023ApJ...956...29Q. doi: 10.3847/1538-4357/ace9b6 .
    9. ↑ Barth, Patrick; Carone, Ludmila; Barnes, Rory; Noack, Lena; Mollière, Paul; Henning, Thomas (2021), "Magma Ocean Evolution of the TRAPPIST-1 Planets", Astrobiology, 21 (11): 1325–1349, arXiv: 2008.09599 , Bibcode:2021AsBio..21.1325B, doi:10.1089/ast.2020.2277, PMID   34314604, S2CID   221246323
    10. ↑ Bourrier, Vincent; de Wit, Julien; Jäger, Mathias (31 August 2017). "Hubble delivers first hints of possible water content of TRAPPIST-1 planets". www.SpaceTelescope.org. Retrieved 4 September 2017.
    11. ↑ PTI (4 September 2017). "First evidence of water found on TRAPPIST-1 planets - The results suggest that the outer planets of the system might still harbour substantial amounts of water. This includes the three planets within the habitable zone of the star, lending further weight to the possibility that they may indeed be habitable". The Indian Express . Retrieved 4 September 2017.
    12. ↑ Wang, Wu, Barclay, Laughlin (2017). "Updated Masses for the TRAPPIST-1 Planets". arXiv: 1704.04290 [astro-ph.EP].{{cite arXiv}}: CS1 maint: multiple names: authors list (link)
    13. ↑ Burgasser, Adam J.; Mamajek, Eric E. (17 August 2017). "On the Age of the TRAPPIST-1 System". The Astrophysical Journal. 845 (2): 110. arXiv: 1706.02018 . Bibcode:2017ApJ...845..110B. doi: 10.3847/1538-4357/aa7fea . S2CID   119464994.
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