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   TRAPPIST-1   
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   TRAPPIST-1   
   PIA21429 - Transit Illustration of TRAPPIST-1 (cropped).jpg   
   Artist's impression of TRAPPIST-1 being transited by two of its seven known   
   planets   
   Observation data   
   Epoch       Equinox   
   Constellation	Aquarius   
   Right ascension	23h 06m 29.283s[1]   
   Declination	−05° 02′ 28.59″[1]   
   Characteristics   
   Evolutionary stage	Main sequence   
   Spectral type	M8V[2]   
   M8.2V[note 1]   
   Apparent magnitude (V)	18.798±0.082[2]   
   Apparent magnitude (R)	16.466±0.065[2]   
   Apparent magnitude (I)	14.024±0.115[2]   
   Apparent magnitude (J)	11.354±0.022[1]   
   Apparent magnitude (H)	10.718±0.021[1]   
   Apparent magnitude (K)	10.296±0.023[1]   
   V−R color index	2.332   
   R−I color index	2.442   
   J−H color index	0.636   
   J−K color index	1.058   
   Astrometry   
   Radial velocity (Rv)	−54±2[2] km/s   
   Proper motion (μ)	RA: 922.1±1.8[2] mas/yr   
   Dec.: −471.9±1.8[2] mas/yr   
   Parallax (π)	82.4 ± 0.8[3] mas   
   Distance	39.6 ± 0.4 ly   
   (12.1 ± 0.1 pc)   
   Absolute magnitude (MV)	18.4±0.1   
   Details   
   Mass	0.089±0.006[3] M☉   
   Radius	0.121±0.003[3] R☉   
   Luminosity (bolometric)	0.000522±0.000019[3] L☉   
   Luminosity (visual, LV)	0.00000373[note 2] L☉   
   Surface gravity (log g)	≈5.227[note 3][4] cgs   
   Temperature	2511±37[5] K   
   Metallicity [Fe/H]	0.04±0.08[5] dex   
   Rotation	3.295±0.003 days[6]   
   Rotational velocity (v sin i)	6[7] km/s   
   Age	7.6±2.2[8] Gyr   
   Other designations   
   2MASS J23062928-0502285, 2MASSI J2306292-050227, 2MASSW J2306292-050227, 2MUDC   
   12171   
   Database references   
   SIMBAD	data   
   Exoplanet Archive	data   
   Extrasolar Planets   
   Encyclopaedia	data   
   TRAPPIST-1, also designated as 2MASS J23062928-0502285,[9] is an ultra-cool   
   red dwarf star[10][11] that is slightly larger but much more massive than the   
   planet Jupiter, located 39.6 light-years (12.1 pc) from the Sun in the   
   constellation Aquarius.[12][   
   13] Seven temperate terrestrial planets have been detected orbiting the star,   
   a larger number than detected in any other planetary system.[14][15] A study   
   released in May 2017 suggests that the tightly packed exoplanets avoid   
   colliding with one another    
   due to orbits that are harmoniously resonant and, as a result, are stable for   
   very long times.[16][17]   
      
   A team of Belgian astronomers first discovered three Earth-sized planets   
   orbiting the dwarf star in 2015. A team led by Michaël Gillon (fr) at the   
   University of Liège in Belgium detected the planets using transit photometry   
   with the Transiting Planets    
   and Planetesimals Small Telescope (TRAPPIST) at the La Silla Observatory in   
   Chile and the Observatoire de l'Oukaïmeden in Morocco.[18][11][19] On 22   
   February 2017, astronomers announced four additional exoplanets around   
   TRAPPIST-1. This work used the    
   Spitzer Space Telescope and the Very Large Telescope at Paranal, among others,   
   and brought the total number of planets to seven, of which three are   
   considered to be within its habitable zone.[20] The others could also be   
   habitable as they may possess    
   liquid water somewhere on their surface.[21][22][23] Depending on definition,   
   up to six could be in the optimistic habitable zone (c, d, e, f, g, h), with   
   estimated equilibrium temperatures of 170 K to 330 K.[24]   
      
   Contents    
   1	Discovery and nomenclature   
   2	Stellar characteristics   
   3	Planetary system   
   3.1	Planetary System Data Charts   
   3.2	Orbital near-resonance   
   3.3	Formation of the planetary system   
   3.4	Tidal locking   
   3.5	Tidal heating   
   3.6	Possible effects of strong X-ray and extreme UV irradiation of the system   
   3.7	Spectroscopy of planetary atmospheres   
   3.8	Impact of stellar activity on habitability   
   3.9	Probability of interplanetary panspermia   
   3.10	Existence of undiscovered planets   
   3.11	Radio signal search   
   4	Moons   
   5	Gallery   
   5.1	Videos   
   6	See also   
   7	Notes   
   8	References   
   9	Further reading   
   10	External links   
   Discovery and nomenclature   
   The star at the center of the system was discovered in 1999 during the Two   
   Micron All-Sky Survey (2MASS).[25][26] It was entered in the subsequent   
   catalog with the designation "2MASS J23062928-0502285". The numbers refer to   
   the right ascension and    
   declination of the star's position in the sky and the "J" refers to the Julian   
   Epoch.   
      
   The system was later studied by a team at the University of Liège, who made   
   their initial observations using the TRAPPIST–South telescope from September   
   to December 2015 and published their findings in the May 2016 issue of the   
   journal Nature.[18][10]    
   The backronym TRAPPIST reflects the telescope's nationality by alluding to   
   Belgium's famous Trappist beer, named after the Roman Catholic religious   
   order, which the astronomers used to toast their discovery.[27][28] Since the   
   star hosted the first    
   exoplanets discovered by this telescope, the discoverers accordingly   
   designated it as "TRAPPIST-1".   
      
   The planets are designated in the order of their discovery, beginning with b   
   for the first planet discovered, c for the second and so on.[29] Three planets   
   around TRAPPIST-1 were first discovered and designated b, c and d in order of   
   increasing orbital    
   periods,[10] and the second batch of discoveries was similarly designated e to   
   h.   
      
   Stellar characteristics   
      
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