TRAPPIST-1e

TRAPPIST-1e
Exoplanet List of exoplanets

Artist's impression of TRAPPIST-1e, depicted here as a tidally locked planet with a liquid ocean. The actual appearance of the exoplanet is currently unknown.
Parent star
Star TRAPPIST-1
Constellation Aquarius
Right ascension (α) 23h 06m 29.283s[1]
Declination (δ) –05° 02′ 28.59″
Apparent magnitude (mV) 18.8
Distance39.5 ± 1.3 ly
(12.1 ±0.4 pc)
Spectral type M8V[2]
Mass (m) 0.08 (± 0.009) M☉
Radius (r) 0.117 (± 0.004) R☉
Temperature (T) 2550 (± 55) K
Metallicity [Fe/H] 0.04 (± 0.08)
Age >0.5 Gyr
Physical characteristics
Mass(m)0.62 (± 0.58) M⊕
Radius(r)0.918 (± 0.039) R⊕
Stellar flux(F⊙)0.662 (± 0.051) ⊕
Density(ρ)4.39 (± 4.19) g cm−3
Surface gravity(g)~0.74 g
Temperature (T) 251.3 K (−21.8 °C; −7.3 °F)
Orbital elements
Semi-major axis(a) 0.02817+0.00083
−0.00087 AU
Eccentricity (e) <0.085
Orbital period(P) 6.099615 ± 0.000011 d
Inclination (i) 89.860+0.10
−0.12°
Other designations
2MASS J23062928-0502285 e, 2MASSI J2306292-050227 e, 2MASSW J2306292-050227 e, 2MUDC 12171 e
Discovery information
Discovery date 22 February 2017
Discoverer(s)
Discovery method Transit
Discovery status Published
Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata
Exoplanet Archivedata
Open Exoplanet Cataloguedata

TRAPPIST-1e, also designated as 2MASS J23062928-0502285 e, is an exoplanet, likely rocky, orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1 approximately 40 light-years (12.1 parsecs, or nearly 3.7336×1014 km) 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.

It was one of seven new exoplanets to be discovered orbiting the star using observations from the Spitzer Space Telescope.[3] The exoplanet is within the star's habitable zone.[4]

Characteristics

Mass, radius, and temperature

TRAPPIST-1e is an Earth-sized exoplanet, meaning it has a mass and radius close to that of Earth. It has an equilibrium temperature of 251.3 K (−22 °C; −7 °F), which is close to Earth's equilibrium temperature. It has a radius of around 0.92 R⊕ and a mass of 0.62 M⊕. These values allow to estimate the standard gravity to be 7.22 m/s2 (74% of Earth value). It also has a similar density to Earth.

Host star

The planet orbits an (late 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 and is at least 500 million years old. In comparison, the Sun is 4.6 billion years old[5] and has a temperature of 5778 K.[6] 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. Therefore, it is too dim to be seen with the naked eye.

Orbit

TRAPPIST-1e orbits its host star with an orbital period of about 6 days and an orbital radius of about 0.028 times that of Earth's (compared to the distance of Mercury from the Sun, which is about 0.38 AU).

Habitability

Artist's impression of the TRAPPIST-1 system, seen from above the surface of one of the planets in the habitable zone.

The exoplanet was announced to be orbiting within the habitable zone of its parent star, the region where, with the correct conditions and atmospheric properties, liquid water may exist on the surface of the planet. TRAPPIST-1e has a radius of around 0.92 R⊕, so it is very likely rocky. Its host star is a red ultracool dwarf, with only about 8% of the mass of the Sun (close to the boundary between brown dwarfs and hydrogen-fusing stars). As a result, stars like TRAPPIST-1 have the ability to live up to 4–5 trillion years, 400–500 times longer than the Sun will live.[7] Because of this ability to live for long periods of time, it is likely TRAPPIST-1 will be one of the last remaining stars when the Universe is much older than it is now, when the gas needed to form new stars will be exhausted, and the remaining ones begin to die off.

The planet is very likely tidally locked, with one side of its hemisphere permanently facing towards the star, while the opposite side is shrouded in eternal darkness. However, between these two intense areas, there would be a sliver of habitability – called the terminator line, where the temperatures may be suitable (about 273 K (0 °C; 32 °F)) for liquid water to exist. Additionally, a much larger portion of the planet may be habitable if it supports a thick enough atmosphere to transfer heat to the side facing away from the star.

See also

References

  1. ↑ Cutri, R.M.; Skrutskie, M.F.; Van Dyk, S.; Beichman, C.A.; Carpenter, J.M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E.L.; Kirkpatrick, J.D.; Light, R.M.; Marsh, K.A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W.A.; Wheelock, S.; Zacarias, N. (June 2003). "2MASS All Sky Catalog of point sources". VizieR Online Data Catalog. European Southern Observatory with data provided by the SAO/NASA Astrophysics Data System. 2246. Bibcode:2003yCat.2246....0C.
  2. ↑ Costa, E.; Mendez, R.A.; Jao, W.-C.; Henry, T.J.; Subasavage, J.P.; Ianna, P.A. (August 4, 2006). "The Solar Neighborhood. XVI. Parallaxes from CTIOPI: Final Results from the 1.5 m Telescope Program" (PDF). The Astronomical Journal. The American Astronomical Society. 132 (3): 1234. Bibcode:2006AJ....132.1234C. doi:10.1086/505706. More than one of |number= and |issue= specified (help)
  3. ↑ Gillon, Michaël; Triaud, Amaury H. M. J.; Demory, Brice-Olivier; Jehin, Emmanuël; Agol, Eric; Deck, Katherine M.; Lederer, Susan M.; Wit, Julien de; Burdanov, Artem (2017). "Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1". Nature. 542 (7642): 456–460. PMID 28230125. doi:10.1038/nature21360.
  4. ↑ "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.
  5. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  6. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  7. ↑ Adams, Fred C.; Laughlin, Gregory; Graves, Genevieve J. M. "Red Dwarfs and the End of the Main Sequence". Gravitational Collapse: From Massive Stars to Planets. Revista Mexicana de Astronomía y Astrofísica. pp. 46–49. Bibcode:2004RMxAC..22...46A.

Coordinates: 23h 06m 29.283s, −05° 02′ 28.59″

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