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The combined transmission spectrum of TRAPPIST-1 b and c rules out a cloud-free hydrogen-dominated atmosphere for each planet, so they are unlikely to harbor an extended gas envelope. Other atmospheres, from a cloud-free water-vapor atmosphere to a Venus-like atmosphere, remain consistent with the featureless spectrum.<ref name="deWit2016"/>
The combined transmission spectrum of TRAPPIST-1 b and c rules out a cloud-free hydrogen-dominated atmosphere for each planet, so they are unlikely to harbor an extended gas envelope. Other atmospheres, from a cloud-free water-vapor atmosphere to a Venus-like atmosphere, remain consistent with the featureless spectrum.<ref name="deWit2016"/>
In 2018, the composition of TRAPPIST-1c was determined, and has been found to be rock-based. The presence of an atmosphere has not yet been confirmed.<ref>{{Cite web|last=Landau|first=NASA, Liz|title=New clues to compositions of TRAPPIST-1 planets|url=https://exoplanets.nasa.gov/news/1481/new-clues-to-compositions-of-trappist-1-planets/|access-date=2021-05-21|website=Exoplanet Exploration: Planets Beyond our Solar System}}</ref><ref name="Grimm2018"/> Observations of the inner planet ] by the ] announced in 2023 suggest that it does not have any significant atmosphere.<ref name="JWST-20230327"/>
In 2018, the composition of TRAPPIST-1c was determined, and has been found to be rock-based. The presence of an atmosphere has not yet been confirmed.<ref>{{Cite web|last=Landau|first=NASA, Liz|title=New clues to compositions of TRAPPIST-1 planets|url=https://exoplanets.nasa.gov/news/1481/new-clues-to-compositions-of-trappist-1-planets/|access-date=2021-05-21|website=Exoplanet Exploration: Planets Beyond our Solar System}}</ref><ref name="Grimm2018"/> Observations of the inner planet ] by the ] announced in 2023 suggest that it does not have any significant atmosphere.<ref name="JWST-20230327">{{cite web |url=https://webbtelescope.org/contents/news-releases/2023/news-2023-110 |title=NASA's Webb Measures the Temperature of a Rocky Exoplanet |date=27 March 2023 |website=webbtelescope.org |publisher=] |access-date=27 March 2023}}</ref>
==See also==
==See also==
Revision as of 23:10, 28 March 2023
Venus-like extrasolar planet orbiting TRAPPIST-1
TRAPPIST-1c
Artist's impression of TRAPPIST-1c (February 2018)
TRAPPIST-1c, also designated as 2MASS J23062928-0502285 c, is a mainly rocky, Venus-like exoplanet orbiting around the ultracool dwarf starTRAPPIST-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, but it is unknown whether it has an atmosphere.
Physical characteristics
Mass, radius, and temperature
TRAPPIST-1c was observed with the transit method, which enabled scientists to calculate its radius. Transit-timing variations and computer simulations were able to determine the mass, density, and gravity of the planet. TRAPPIST-1c is the third-largest planet of the TRAPPIST-1 system, with a radius of 1.097 R🜨. It is also the third-most massive of the system, with a mass of 1.308 M🜨, slightly lower than that of the next most massive, TRAPPIST-1g. Initial estimates suggested that TRAPPIST-1c has a lower density (4.89 g/cm) and gravity (0.966g) than Earth, consistent with a rock-based composition and a thick, Venus-like atmosphere. TRAPPIST-1c's atmosphere was expected to be large enough to raise its surface temperature far above the calculated 334.8 K (61.7 °C; 143.0 °F) equilibrium temperature. However, refined density estimates show that the planet's density is similar to Earth. In addition, the planet may be very geologically active due to tidal squeezing similar to Jupiter's moon Io, which happens to have a similar orbital period and eccentricity (see TRAPPIST-1#Resonance for references).
Orbit
The orbit of TRAPPIST-1c is very close to its host star. One year on this planet lasts a mere 2.42 days (58 hours), a fraction as long as that of our Solar System's innermost planet, Mercury. The planet orbits at a distance of 0.0158 AU, which is about 1.6% the distance between Earth and the Sun. At this proximity, TRAPPIST-1c is most likely tidally locked. However, due to the small size of its host star, the planet only receives about 2.1 times the sunlight as Earth (similar to Venus, at 1.9 times). Its orbital eccentricity is very low at 0.00654, similar to that of TRAPPIST-1b.
Host star
TRAPPIST-1c orbits the ultracool dwarf star TRAPPIST-1. It is 0.121 R☉ and 0.089 M☉, with a temperature of 2511 K and an age between 3 and 8 billion years. For comparison, the Sun has a temperature of 5778 K and is about 4.5 billion years old. TRAPPIST-1 is also very dim, with about 0.0005 times (0.05%) the luminosity of the Sun. It is too faint to be see with the naked eye, having an apparent magnitude of 18.80.
Atmosphere
The combined transmission spectrum of TRAPPIST-1 b and c rules out a cloud-free hydrogen-dominated atmosphere for each planet, so they are unlikely to harbor an extended gas envelope. Other atmospheres, from a cloud-free water-vapor atmosphere to a Venus-like atmosphere, remain consistent with the featureless spectrum.
In 2018, the composition of TRAPPIST-1c was determined, and has been found to be rock-based. The presence of an atmosphere has not yet been confirmed. Observations of the inner planet TRAPPIST-1b by the James Webb Space Telescope announced in 2023 suggest that it does not have any significant atmosphere.
Artist's impression of TRAPPIST-1c (February 2018)
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