Trappist-1

from Wikipedia, the free encyclopedia
Star
Trappist-1
Size comparison between the sun (left) and Trappist-1
Size comparison between the sun (left) and Trappist-1
Approx. Position of Trappist-1 in Aquarius
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Aquarius
Right ascension 23 h 06 m 29.37 s
declination -05 ° 02 ′ 29 ″
Apparent brightness 18.8 mag
Typing
Known exoplanets 7th
R − I index 2.44 
Spectral class M8
Astrometry
Radial velocity (−56.3 ± 3) km / s
parallax (80.45 ± 0.12)  mas
distance (40.52 ± 0.06)  Lj
(12.43 ± 0.02)  pc
Proper movement 
Rec. Share: (930.88 ± 0.25)  mas / a
Dec. portion: (−479.40 ± 0.17)  mas / a
Physical Properties
Dimensions 0.089 ± 0.007  M ☉
radius 0.121 ± 0.003  R ☉
Luminosity

(5.22 ± 0.19 × 10 −4 )  L ☉

Effective temperature (2511 ± 37)  K.
Metallicity [Fe / H] 0.04 ± 0.08
Age 7.6 ± 2.2 bill.  A
Other names
and catalog entries
2MASS catalog 2MASS J23062928-0502285 [1]

Trappist-1 is about 40 light years from the Earth distant planetary system . After initially only the central star, a low-mass red dwarf (an ultra-cool dwarf ), had been discovered in the Two Micron All Sky Survey in 1999 and had been given the catalog designation 2MASS J23062928-0502285 , the planetary system became after further research with the Transiting Planets and Planetesimals Small Telescope ( TRAPPIST ) at the La Silla Observatory in Chile named Trappist-1 .

A team of astronomers led by Michaël Gillon from the Institut d'Astrophysique et Géophysique at the University of Liège in Belgium found in 2016 that this dark and cool star gradually decreased in brightness, suggesting that several objects were between the Star and Earth go by. Initial studies using the transit method initially revealed evidence of three Earth-like planets orbiting the star. On February 22, 2017, NASA announced the discovery of four more Earth-like planets. The discovery was the result of weeks of observation by Trappist-1 using the Spitzer Space Telescope .

The star Trappist-1 a

The star Trappist-1 a is a very small and faint red dwarf star . It is only about one twelfth the mass and one ninth the diameter of the sun . Its surface temperature is about 2550  K . Due to its small size and temperature, its total brightness is about one 250,000th that of the sun.

Although it is relatively close to us on a cosmic scale at a distance of around 40 light years , it can only be observed with the most powerful telescopes due to its low luminosity, because its apparent brightness is only around 19 mag. In telescopes it appears dark red with a high proportion of infrared radiation .

Since, from our point of view, its planets can pass in front of it , our own solar system is very precisely in the orbital plane of its planets (the same happens to be the other way round, because the star is very close to the ecliptic , but not so close that it is around March 5th would be covered by the sun for observers on earth) and thus we are probably also approximately in the equatorial plane of the star. A value of 6 km / s was measured for its projected equatorial rotation speed v ∙ sin i , which should therefore also come close to the real equatorial rotation speed.

Another special feature is that Trappist-1 moves across the sky for observers on earth with a relatively fast proper movement of 1.04 arc seconds / year. In connection with its radial speed of −56 km / s, this means that the star is moving obliquely past us in space at a speed of 82 km / s relative to our sun. If this movement is maintained, the star will reach its closest approach to the Sun after about 100,000 years and then be only about 29 light-years away. In its closest proximity, however, it will only appear slightly brighter by 0.6 may.

The age of the system was estimated to be 7.6 ± 2.2 billion years in a publication published in June 2017.

Planetary system

The two innermost planets have orbital periods of about 1.5 and 2.4 days, that of the seventh planet is in the range of 20 days. The distances to its star are between one hundredth and one twentieth of the distance between the earth and the sun. The structure of this planetary system is therefore more similar to the system of Jupiter's moons than our solar system. The planets orbit Trappist-1a presumably in a bound rotation . In addition to a 1: 1 constellation (orbital period of the satellite: period of rotation) as in the Earth-Moon system, in which the satellite always faces the same side of its parent star, there are also constellations of spin-orbit resonance , e.g. B. 3: 2 or 5: 3, conceivable. In a 1: 1 constellation, a planet would always show the same side of the sun, which can lead to extreme temperature differences. In a dense atmosphere, these would be somewhat balanced out by strong winds and life would be possible especially on the day-night border . A spin orbit resonance would not have such serious effects.

However, since the star is much fainter than the sun, the two inner planets receive, despite their proximity to the star, only four or two times the amount of radiation that hits the earth. Yet they are closer to the star than the habitable zone of this system. However, it is possible that habitable regions exist on their surfaces. The combined transmission spectrum of Trappist-1 b and c revealed a cloud-free, hydrogen-based atmosphere for these two planets. NASA assumes that the planets Trappist-1 e, f and g are in the habitable zone.

Since red dwarfs get much older than sun-like stars, life on planets would also have much more time to evolve from them. The astronomer Michaël Gillon who was involved in the discovery sees systems comparable to Trappist-1 as the most promising candidates for possible life.

Artistic representation based on actual proportions

Trappist-1 b

Luminosity curves of Trappist-1 a through coverage by the individual planets

With an equilibrium temperature of around 400  K (127 ° C), the planet closest to the Sun is too hot for liquid water.

Trappist-1 c

Its density is comparable to that of the earth , which indicates a large iron core . Liquid water can occur on the side facing away from the sun.

Trappist-1 d

Along with Trappist-1 h, Trappist-1 d belongs to the two smallest known planets of the system and lies on the sun side near the limit of the habitable zone. Its sun-turned side could possibly still harbor life.

Trappist-1 e

Trappist-1 e lies in the habitable zone, also with a density comparable to that of the earth.

Trappist-1 f

Trappist-1 f lies on the outer edge of the habitable zone. It has a lower density than Earth and is possibly an ocean world , the side of which is turned away from the sun is covered by an ice crust.

Trappist-1 g

Trappist-1 g is also located on the outer edge of the habitable zone, but on its side facing the sun, assuming an earth-like atmosphere, there should be life-friendly temperatures. It is slightly larger and more massive than Earth, although its density is lower.

Trappist-1 h

Trappist-1 h is the farthest known planet from the star. Its size is comparable to Trappist-1 d. Because of its distance, it is likely too cold for liquid water on its surface.

Size comparison of the Jupiter system (top) with the Trappist 1 system (middle). Below is a size comparison to the solar system, reduced by a factor of 25. The planets are shown greatly enlarged in relation to the orbits.
Trappist 1 planet
Planet
(order
from the star) 		Discovered Mass
( earth masses ) 		Radius
( earth radii ) 		Major semiaxis of
the railway
( AU ) 		Rotation time
( days ) 		eccentricity Orbit inclination
( degree ) 		Equilibrium
temperature
( Kelvin )
b 2016 1.02   +0.15−0.14 1.12 ± 0.03 0.0115 1.51 <0.081 89.65   +0.22−0.27 391.8 ± 5.5
c 2016 1.16   +0.14−0.13 1.10 ± 0.03 0.0158 2.42 <0.083 89.67 ± 0.17 334.8 ± 4.7
d 2016 0.30 ± 0.04 0.78 ± 0.02 0.0223 4.05 <0.070 89.75 ± 0.16 282.1 ± 4.0
e 2017 0.77 ± 0.08 0.91 ± 0.03 0.0293 6.10 <0.085 89.86   +0.10−0.12 246.1 ± 3.5
f 2017 0.93 ± 0.08 1.05 ± 0.03 0.0385 9.21 <0.063 89.680 ± 0.034 214.5 ± 3.0
G 2017 1.15 ± 0.10 1.15 ± 0.03 0.0469 12.35 <0.061 89.710 ± 0.025 194.5 ± 2.7
H 2017 0.33   +0.06−0.05 0.77 ± 0.03 0.0619 18.77 unknown 89.76   +0.05−0.04 169.2 ± 2.4

See also

literature

  • Michaël Gillon, Emmanuël Jehin, Susan M. Lederer, Laetitia Delrez, Julien de Wit, Artem Burdanov, Valérie Van Grootel, Adam J. Burgasser, Amaury HMJ Triaud, Cyrielle Opitom, Brice-Olivier Demory, Devendra K. Sahu, Daniella Bardalez Gagliuffi , Pierre Magain, Didier Queloz : Temperate Earth-sized planets transiting a nearby ultracool dwarf star . In: Nature . 2016, doi : 10.1038 / nature17448 ( eso.org [PDF]).

Web links

Commons : TRAPPIST-1  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b c d TRAPPIST-1. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed December 2, 2018 .
  2. ↑ E. Costa, RA Méndez, W.-C. Jao, TJ Henry, JP Subasavage, PA Ianna: The Solar Neighborhood. XVI. Parallaxes from CTIOPI: Final Results from the 1.5 m Telescope Program. In: The Astronomical Journal. Vol. 132, 2006, doi: 10.1086 / 505706 , pp. 1234-1247, bibcode : 2006AJ .... 132.1234C .
  3. ^ VizieR: Activity and kinematics of ultracool dwarfs (Schmidt +, 2007)
  4. ↑ VizieR: Volume-limited sample of M7-M9.5 dwarfs <20pc (Reiners +, 2009)
  5. ↑ a b c d e f Laetitia Delrez, Michael Gillon, Amaury HMJ, Triaud Brice-Oliver Demory, Julien de Wit, James Ingalls, Eric Agol, Emeline Bolmont, Artem Burdanov, Adam J. Burgasser, Sean J. Carey, Emmanuel Jehin , Jeremy Leconte, Susan Lederer, Didier Queloz, Franck Selsis, Valerie Van Grootel: Early 2017 observations of TRAPPIST-1 with Spitzer . In: Monthly Notices of the Royal Astronomical Society . 475, No. 3, April 2018, pp. 3577-3597. arxiv : 1801.02554 . bibcode : 2018MNRAS.475.3577D . doi : 10.1093 / mnras / sty051 .
  6. ↑ a b TRAPPIST-1. In: NASA Exoplanet Archive . Retrieved April 22, 2019 .
  7. ^ A b Adam J. Burgasser, Eric E. Mamajek: On the Age of the TRAPPIST-1 System (draft, submitted to the Astrophysical Journal). June 8, 2017. Retrieved August 20, 2017 . ( arxiv : 1706.02018v1 )
  8. ↑ TRAPPIST-1b. In: openexoplanetcatalogue.com. Open Exoplanet Catalog, accessed May 4, 2016 .
  9. ↑ http://www.astronews.com/frag/lösungen/4/frage4170.html
  10. ↑ Helga Rietz and Christian Speicher: Trappist-1-Planetensystem: Seven answers to seven exoplanets In: Neue Zürcher Zeitung of February 23, 2017
  11. ↑ information@eso.org: Three Potentially Habitable Worlds Found Around Nearby Ultracool Dwarf Star - Currently the best place to search for life beyond the Solar System. In: eso.org. Retrieved May 2, 2016, May 4, 2016 (UK English).
  12. ↑ Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature from February 22, 2017.
  13. ↑ NASA: NASA telescope reveals largest batch of Earth-size, habitable-zone planets around single star. In: exoplanets.nasa.gov. February 22, 2017. Retrieved February 22, 2017 (American English).
  14. ↑ VizieR: Rotation and variability of substellar objects (Crossfield, 2014)
  15. ↑ TRAPPIST-1 is almost twice as old as the sun. scinexx.de, August 17, 2017, accessed on August 20, 2017 .
  16. ↑ A. Jokes: These seven alien worlds could help explain how planets form . In: Nature . February 22, 2017. doi : 10.1038 / nature.2017.21512 .
  17. ↑ J. de Wit, HR Wakeford, M. Gillon, NK Lewis, JA Valenti, B.-O. Demory, AJ Burgasser, A. Burdanov, L. Delrez, E. Jehin, SM Lederer, D. Queloz, AHMJ Triaud, V. Van Grootel: A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c. In: Nature. Vol. 537, 2016, doi: 10.1038 / nature18641 , pp. 69–72, bibcode : 2016Natur.537 ... 69D .
  18. ^ Three Potentially Habitable Worlds Found Around Nearby Ultracool Dwarf Star - Currently the best place to search for life beyond the Solar System. European Southern Observatory, May 2, 2016, accessed February 24, 2017 .
  19. ↑ a b c Simon L. Grimm, Brice-Olivier Demory, Michaël Gillon, Caroline Dorn, Eric Agol, Artem Burdanov, Laetitia Delrez, Marko Sestovic, Amaury HMJ Triaud, Maritn Turbet, Émeline Bolmont, Anthony Caldas, Julien de Wit, Emmanuël Jehin, Jérémy Leconte, Sean N. Raymond, Valérie Van Grootel, Adam J. Burgasser, Sean Carey, Daniel Fabrycky, Kevin Heng, David M. Hernandez, James G. Ingalls, Susan Lederer, Franck Selsis, Didier Queloz: The nature of the TRAPPIST-1 exoplanets . In: Astronomy & Astrophysics . 613, January 21, 2018, p. A68. arxiv : 1802.01377 . bibcode : 2018A & A ... 613A..68G . doi : 10.1051 / 0004-6361 / 201732233 .