TRAPPIST-1b

TRAPPIST-1b
	Earth and TRAPPIST-1b compared
Discovery
Discovered by	Michaël Gillon et al.
Discovery site	TRAPPIST
Discovery date	May 2, 2016
Detection method	Transit
Orbital characteristics
Semi-major axis	0.01154 ± 0.00010 AU (1,726,000 ± 15,000 km)
Eccentricity	0.00622±0.00304
Orbital period (sidereal)	1.510826 ± 0.000006 d (36.25982 ± 0.00014 h)
Inclination	89.728°±0.165°
Argument of periastron	336.86°±34.24°
Star	TRAPPIST-1
Physical characteristics
Mean radius	1.116+0.014; −0.012 R🜨
Mass	1.374±0.069 M🜨
Mean density	5.425+0.265; −0.272 g/cm3
Surface gravity	1.102±0.052 g; 10.80±0.51 m/s2
Temperature	397.6±3.8 K (124.5 °C; 256.0 °F, equilibrium); 503+26; −27 K (230 °C; 446 °F, surface)
Atmosphere
Composition by volume	None or extremely thin

TRAPPIST-1b is a mainly rocky exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years (12.5 parsecs) 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,^[1] and later studies were able to refine its physical parameters.

The planet is about 37% more massive than Earth and about 39% larger in volume; thus its density is very similar. It is the innermost of seven planets orbiting TRAPPIST-1, all of which are terrestrial, but is too close to its star to be in the habitable zone. Observations by the James Webb Space Telescope announced in 2023 suggest that it does not have any significant atmosphere.^[6]^[7] Its albedo is very low, making it dark in color.

^ ^a ^b Cite error: The named reference Gillon2016 was invoked but never defined (see the help page).
^ ^a ^b Cite error: The named reference Agol2021 was invoked but never defined (see the help page).
^ ^a ^b Cite error: The named reference Grimm2018 was invoked but never defined (see the help page).
^ Cite error: The named reference vangrootel2017 was invoked but never defined (see the help page).
^ Cite error: The named reference Ducrot2020 was invoked but never defined (see the help page).
^ ^a ^b ^c Cite error: The named reference Greene2023 was invoked but never defined (see the help page).
^ ^a ^b Cite error: The named reference JWST-20230327 was invoked but never defined (see the help page).

[Gillon2016-1] Cite error: The named reference Gillon2016 was invoked but never defined (see the help page).

[Agol2021-2] Cite error: The named reference Agol2021 was invoked but never defined (see the help page).

[Grimm2018-3] Cite error: The named reference Grimm2018 was invoked but never defined (see the help page).

[vangrootel2017-4] Cite error: The named reference vangrootel2017 was invoked but never defined (see the help page).

[Ducrot2020-5] Cite error: The named reference Ducrot2020 was invoked but never defined (see the help page).

[Greene2023-6] Cite error: The named reference Greene2023 was invoked but never defined (see the help page).

[JWST-20230327-7] Cite error: The named reference JWST-20230327 was invoked but never defined (see the help page).

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Discovery^[1]
Earth and TRAPPIST-1b compared
Discovered by	Michaël Gillon et al.
Discovery site	TRAPPIST
Discovery date	May 2, 2016
Detection method	Transit
Orbital characteristics^[2]
Semi-major axis	0.01154 ± 0.00010 AU (1,726,000 ± 15,000 km)
Eccentricity	0.00622±0.00304^[3]
Orbital period (sidereal)	1.510826 ± 0.000006 d (36.25982 ± 0.00014 h)
Inclination	89.728°±0.165°
Argument of periastron	336.86°±34.24°^[3]
Star	TRAPPIST-1^[4]
Physical characteristics^[2]
Mean radius	1.116+0.014 −0.012 R_🜨
Mass	1.374±0.069 M_🜨
Mean density	5.425+0.265 −0.272 g/cm³
Surface gravity	1.102±0.052 g 10.80±0.51 m/s²
Temperature	397.6±3.8 K (124.5 °C; 256.0 °F, equilibrium)^[5] 503+26 −27 K (230 °C; 446 °F, surface)^[6]
Atmosphere
Composition by volume	None or extremely thin^[6]^[7]