TRAPPIST-1d

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TRAPPIST-1d
TRAPPIST-1d artist impression 2018.png
Artist's impression of TRAPPIST-1d (February 2018).
Discovery [1]
Discovered by Michaël Gillon et al.
Discovery site TRAPPIST
Discovery dateMay 2, 2016
Transit
Orbital characteristics [2]
0.02227±0.00019  AU
Eccentricity 0.00837±0.00093 [3]
4.049219±0.000026  d
Inclination 89.896°±0.077°
−8.73°±6.17° [3]
Star TRAPPIST-1 [4]
Physical characteristics [2]
0.788+0.011
−0.010  R🜨
Mass 0.388±0.012  M🜨
Mean density
4.354+0.156
−0.163  g/cm3
0.624±0.019 g
6.11±0.19  m/s2
Temperature Teq: 286.2±2.8  K (13.1 °C; 55.5 °F) [5]

    TRAPPIST-1d is a small exoplanet (about 40 percent the mass of the Earth), which orbits on the inner edge of the habitable zone of the ultracool dwarf star TRAPPIST-1, located 40.7 light-years (12.5 parsecs ) away from Earth in the constellation of Aquarius. The exoplanet was found by using the transit method. The first signs of the planet were announced in 2016, but it was not until the following years that more information concerning the probable nature of the planet was obtained. TRAPPIST-1d is the second-least massive planet of the system and is likely to have a compact hydrogen-poor atmosphere similar to Venus, Earth, or Mars. [6] It receives just 4.3% more sunlight than Earth, placing it on the inner edge of the habitable zone. [7] It has about <5% of its mass as a volatile layer, which could consist of atmosphere, oceans, and/or ice layers. [3] A 2018 study by the University of Washington concluded that TRAPPIST-1d might be a Venus-like exoplanet with an uninhabitable atmosphere. [8] The planet is an eyeball planet candidate. [9]

    Contents

    Physical characteristics

    Radius, mass, and temperature

    TRAPPIST-1d was detected with the transit method, allowing scientists to accurately determine its radius. The planet is about 0.788  R🜨 with a small error margin of about 70 km. Transit timing variations and complex computer simulations helped accurately determine the mass of the planet, which led to scientists being able to calculate its density, surface gravity, and composition. TRAPPIST-1d is a mere 0.388  M🜨 , making it one of the least massive exoplanets yet found. [2] Initial estimates suggested that it has 61.6% the density of Earth (3.39 g/cm3) and just under half the gravity. Compared to Mars, it has nearly three times that planet's mass but was thought to still be significantly less dense, which would indicate the presence of a significant atmosphere; models of the low density of TRAPPIST-1d indicated a mainly rocky composition, but with about ≤5% of its mass in the form of a volatile layer. The volatile layer of TRAPPIST-1d may consist of atmosphere, ocean, and/or ice layers. [3] However, refined estimates show that the planet is more dense, closer to 79.2% of Earth's bulk density (4.35  g/cm3 ). [2] TRAPPIST-1d has an equilibrium temperature of 282.1 K (9.0 °C; 48.1 °F), assuming an albedo of 0. [7] For an Earth-like albedo of 0.3, the planet's equilibrium temperature is around 258 K (−15 °C; 5 °F), very similar to Earth's at 255 K (−18 °C; −1 °F). [10]

    Orbit

    TRAPPIST-1d is a closely orbiting planet, with one full orbit taking just 4.05 days (about 97 hours) to complete. [7] It orbits at a distance of just 0.02228 AU from the host star, or about 2.2% the distance between Earth and the Sun. [3] For comparison, Mercury, the Solar System's innermost planet, takes 88 days to orbit at a distance of about 0.38 AU. The size of TRAPPIST-1 and the close orbit of TRAPPIST-1d around it means that the star as seen from the planet appears 5.5 times as large as the Sun from the Earth. While a planet at TRAPPIST-1d's distance from the Sun would be a scorched world, the low luminosity of TRAPPIST-1 means that the planet gets only 1.043 times the sunlight that Earth receives, placing it within the inner part of the conservative habitable zone. [7]

    Host star

    The planet orbits an (M-type) ultracool dwarf star named TRAPPIST-1. The star has a mass of 0.089 M☉ (close to the boundary between brown dwarfs and hydrogen-fusing stars) and a radius of 0.121 R☉. It has a temperature of 2,516 K (2,243 °C; 4,069 °F), and is between 3 and 8 billion years old. In comparison, the Sun is 4.6 billion years old [11] and has a temperature of 5778 K (5504.85 °C, 9940.73 °F). [12] 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 metals than the Sun. Its luminosity (L☉) is 0.05% of that of the Sun.

    Stars like TRAPPIST-1 have the ability to live up to 4–5 trillion years, 400–500 times longer than the Sun will live (the Sun only has about 8 billion years of lifespan left, slightly more than half of its lifetime). [13] 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 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 (the limit for that is 6.5).

    The star is not just very small and far away, it also emits comparatively little visible light, mainly shining in the invisible infrared. Even from the close in proximity of TRAPPIST-1d, about 50 times closer than Earth is from the Sun, the planet receives less than 1% the visible light Earth sees from the Sun. This would probably make the days on TRAPPIST-1d never brighter than twilight is on Earth. However, that still means that TRAPPIST-1 could easily shine at least 3000 times brighter in the sky of TRAPPIST-1d than the full moon does in Earth's night sky.

    Habitability

    Models and scientists are divided on whether their convergent solutions from the data for TRAPPIST-1d indicates Earth-like habitability or a severe greenhouse effect.

    In some respects, this exoplanet is one of the most Earth-like found. It does not have a hydrogen or helium-based atmosphere, which makes larger planets uninhabitable (the planet is not massive enough to retain light gases).

    The planet is located at the inner edge of the expected habitable zone of its parent star (where liquid water can reasonably be expected to exist on its surface, if present). The planet may also have liquid and atmospheric water, up to many times more than Earth. [3] However, some three-dimensional modeling solutions have a little water surviving beyond the early hot phase in the planet's history. [14] [15] Most models by the University of Washington for TRAPPIST-1d strongly converge on a Venus-like planet (runaway greenhouse effect) with an uninhabitable atmosphere.

    Because TRAPPIST-1d is only ~30% the Earth's mass, it, like Venus and Mars, may have no magnetic field, which would allow the parent star's solar wind to strip away the more volatile components of its atmosphere (including water), leaving it hydrogen-poor like those planets. [8] However, due to its close orbit, TRAPPIST-1d is likely tidally locked and it may be very geologically active due to tidal squeezing as happens to Jupiter's moon Io and the volcanic gases could replenish the atmosphere lost to the solar wind. TRAPPIST-1d may resist this the tidal heating, especially if it has an Earth-like albedo of ≥0.3, according to other analyses. The same researchers point out that such proximity to the host star tends to increase geothermal activity, and tidally heat the bottom of any seas. [16] If the planet has suffered a runaway greenhouse, its atmosphere should be thinner and cooler than Venus', due to its smaller mass and the fact it only receives about as much radiation as the Earth (while Venus receives about twice as much).

    The lack of a magnetic field will also result in the surface receiving more charged particles than the Earth does. And if the planet is tidally locked, a dense atmosphere could be enough to transfer heat from the illuminated side to the much colder dark side.

    Discovery

    A team of astronomers headed by Michaël Gillon of the Institut d’Astrophysique et Géophysique at the University of Liège [17] in Belgium used the TRAPPIST (Transiting Planets and Planetesimals Small Telescope) telescope at the La Silla Observatory in the Atacama Desert, Chile, [18] to observe TRAPPIST-1 and search for orbiting planets. By utilising transit photometry, they discovered three Earth-sized planets orbiting the dwarf star; the innermost two are tidally locked to their host star while the outermost appears to lie either within the system's habitable zone or just outside of it. [19] [20] The team made their observations from September to December 2015 and published its findings in the May 2016 issue of the journal Nature . [18] [21]

    The original claim and presumed size of the planet was revised when the full seven-planet system was revealed in 2017:

    Artist's impression of the TRAPPIST-1 planetary system. PIA22093-TRAPPIST-1-PlanetLineup-20180205.jpg
    Artist's impression of the TRAPPIST-1 planetary system.
    "We already knew that TRAPPIST-1, a small, faint star some 40 light years away, was special. In May 2016, a team led by Michaël Gillon at Belgium’s University of Liege announced it was closely orbited by three planets that are probably rocky: TRAPPIST-1b, c and d...
    "As the team kept watching shadow after shadow cross the star, three planets no longer seemed like enough to explain the pattern. “At some point we could not make sense of all these transits,” Gillon says.
    "Now, after using the space-based Spitzer telescope to stare at the system for almost three weeks straight, Gillon and his team have solved the problem: TRAPPIST-1 has four more planets.
    "The planets closest to the star, TRAPPIST-1b and c, are unchanged. But there’s a new third planet, which has taken the d moniker, and what had looked like d before turned out to be glimpses of e, f and g. There’s a planet h, too, drifting farthest away and only spotted once." [22]

    See also

    Related Research Articles

    <span class="mw-page-title-main">Transit-timing variation</span> Exoplanet detection method using transit timing variations

    Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small as that of Earth. In tightly packed planetary systems, the gravitational pull of the planets among themselves causes one planet to accelerate and another planet to decelerate along its orbit. The acceleration causes the orbital period of each planet to change. Detecting this effect by measuring the change is known as transit-timing variations. "Timing variation" asks whether the transit occurs with strict periodicity or if there exists a variation.

    <span class="mw-page-title-main">TRAPPIST</span> Pair of Belgian optic robotic telescopes

    The Transiting Planets and Planetesimals Small Telescope (TRAPPIST) is the corporate name for a pair of Belgian optic robotic telescopes. TRAPPIST–South, which is situated high in the Chilean mountains at ESO's La Silla Observatory, came online in 2010, and TRAPPIST–North situated at the Oukaïmeden Observatory in the Atlas Mountains in Morocco, came online in 2016.

    <span class="mw-page-title-main">Habitability of red dwarf systems</span> Possible factors for life around red dwarf stars

    The theorized habitability of red dwarf systems is determined by a large number of factors. Modern evidence suggests that planets in red dwarf systems are unlikely to be habitable, due to their low stellar flux, high probability of tidal locking, likely lack of magnetospheres and atmospheres, and the high stellar variation such planets would experience. However, the sheer number and longevity of red dwarfs could provide ample opportunity to realize any small possibility of habitability.

    <span class="mw-page-title-main">TRAPPIST-1</span> Ultra-cool red dwarf star in the constellation Aquarius

    TRAPPIST-1 is a cool red dwarf star with seven known exoplanets. It lies in the constellation Aquarius about 40.66 light-years away from Earth, and has a surface temperature of about 2,566 K. Its radius is slightly larger than Jupiter and it has a mass of about 9% of the Sun. It is estimated to be 7.6 billion years old, making it older than the Solar System. The discovery of the star was first published in 2000.

    <span class="mw-page-title-main">SPECULOOS</span> Astronomical observatory

    SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) is a project consisting of SPECULOOS Southern Observatory (SSO) at the Paranal Observatory in Chile and SPECULOOS Northern Observatory (SNO) at the Teide Observatory in Tenerife.

    <span class="mw-page-title-main">TRAPPIST-1b</span> Rocky exoplanet orbiting TRAPPIST-1

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

    <span class="mw-page-title-main">TRAPPIST-1c</span> Rocky exoplanet orbiting TRAPPIST-1

    TRAPPIST-1c, also designated as 2MASS J23062928-0502285 c, is a mainly rocky exoplanet orbiting around the ultracool dwarf star TRAPPIST-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, and observations by the James Webb Space Telescope announced in 2023 suggests against a thick CO2 atmosphere, however this does not exclude a thick abiotic oxygen-dominated atmosphere as is hypothesized to be common around red dwarf stars.

    <span class="mw-page-title-main">Ultra-cool dwarf</span> Class-M stars with a temperature below 2,700 K

    An ultra-cool dwarf is a stellar or sub-stellar object that has an effective temperature lower than 2,700 K . This category of dwarf stars was introduced in 1997 by J. Davy Kirkpatrick, Todd J. Henry, and Michael J. Irwin. It originally included very low mass M-dwarf stars with spectral types of M7 but was later expanded to encompass stars ranging from the coldest known to brown dwarfs as cool as spectral type T6.5. Altogether, ultra-cool dwarfs represent about 15% of the astronomical objects in the stellar neighborhood of the Sun. One of the best known examples is TRAPPIST-1.

    <span class="mw-page-title-main">TRAPPIST-1f</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1f, also designated as 2MASS J23062928-0502285 f, is an exoplanet, likely rocky, orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years 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.

    <span class="mw-page-title-main">TRAPPIST-1g</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1g, also designated as 2MASS J23062928-0502285 g and K2-112 g, is an exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation Aquarius. It was one of four new exoplanets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope. The exoplanet is within the optimistic habitable zone of its host star. It 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.

    <span class="mw-page-title-main">TRAPPIST-1e</span> Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1e, also designated as 2MASS J23062928-0502285 e, is a rocky, close-to-Earth-sized exoplanet orbiting within the habitable zone around the ultracool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. Astronomers used the transit method to find the exoplanet, a method that measures the dimming of a star when a planet crosses in front of it.

    <span class="mw-page-title-main">TRAPPIST-1h</span> Cold Earth-size exoplanet orbiting TRAPPIST-1

    TRAPPIST-1h, also designated as 2MASS J23062928-0502285 h, is an exoplanet orbiting around the ultra-cool dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation Aquarius. It was one of four new exoplanets to be discovered orbiting the star in 2017 using observations from the Spitzer Space Telescope. In the following years, more studies were able to refine its physical parameters.

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    <span class="mw-page-title-main">Ross 128 b</span> Confirmed terrestrial exoplanet orbiting Ross 128

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    References

    1. ↑ Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M.; Delrez, Laetitia; et al. (May 2016). "Temperate Earth-sized planets transiting a nearby ultracool dwarf star". Nature. 533 (7602): 221–224. arXiv: 1605.07211 . Bibcode:2016Natur.533..221G. doi:10.1038/nature17448. ISSN   1476-4687. PMC   5321506 . PMID   27135924.
    2. 1 2 3 4 Agol, Eric; Dorn, Caroline; Grimm, Simon L.; Turbet, Martin; et al. (1 February 2021). "Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides". The Planetary Science Journal. 2 (1): 1. arXiv: 2010.01074 . Bibcode:2021PSJ.....2....1A. doi: 10.3847/psj/abd022 . S2CID   222125312.
    3. 1 2 3 4 5 6 Grimm, Simon L.; Demory, Brice-Olivier; Gillon, Michael; Dorn, Caroline; Agol, Eric; Burdanov, Artem; Delrez, Laetitia; Sestovic, Marko; Triaud, Amaury H.M.J.; Turbet, Martin; Bolmont, Emeline; Caldas, Anthony; de Wit, Julien; Jehin, Emmanuel; Leconte, Jeremy; Raymond, Sean N.; Van Grootel, Valerie; Burgasser, Adam J.; Carey, Sean; Fabrycky, Daniel; Heng, Kevin; Hernandez, David M.; Ingalls, James G.; Lederer, Susan; Selsis, Franck; Queloz, Didier (5 February 2018). "The nature of the TRAPPIST-1 exoplanets". Astronomy & Astrophysics. 613: A68. arXiv: 1802.01377 . Bibcode:2018A&A...613A..68G. doi:10.1051/0004-6361/201732233. S2CID   3441829.
    4. ↑ Van Grootel, Valerie; Fernandes, Catarina S.; Gillon, Michaël; Jehin, Emmanuel; Scuflaire, Richard; et al. (5 December 2017). "Stellar Parameters for Trappist-1". The Astrophysical Journal. 853 (1): 30. arXiv: 1712.01911 . Bibcode:2018ApJ...853...30V. doi: 10.3847/1538-4357/aaa023 . S2CID   54034373.
    5. ↑ Ducrot, E.; Gillon, M.; Delrez, L.; Agol, E.; et al. (1 August 2020). "TRAPPIST-1: Global results of the Spitzer Exploration Science Program Red Worlds". Astronomy & Astrophysics. 640: A112. arXiv: 2006.13826 . Bibcode:2020A&A...640A.112D. doi:10.1051/0004-6361/201937392. ISSN   0004-6361. S2CID   220041987.
    6. ↑ February 2018, Elizabeth Howell 07 (7 February 2018). "Rocky-Planet-Like Atmospheres Are Possible on 3 TRAPPIST-1 Planets". Space.com. Retrieved 10 February 2021.{{cite web}}: CS1 maint: numeric names: authors list (link)
    7. 1 2 3 4 Delrez, Laetitia; Gillon, Michael; H.M.J, Amaury; Brice-Oliver Demory, Triaud; de Wit, Julien; Ingalls, James; Agol, Eric; Bolmont, Emeline; Burdanov, Artem; Burgasser, Adam J.; Carey, Sean J.; Jehin, Emmanuel; Leconte, Jeremy; Lederer, Susan; Queloz, Didier; Selsis, Franck; Grootel, Valerie Van (9 January 2018). "Early 2017 observations of TRAPPIST-1 with Spitzer". Monthly Notices of the Royal Astronomical Society. 475 (3): 3577–3597. arXiv: 1801.02554 . Bibcode:2018MNRAS.475.3577D. doi: 10.1093/mnras/sty051 .
    8. 1 2 "Study brings new climate models of small star TRAPPIST 1's seven intriguing worlds".
    9. ↑ Anders, Charlie Jane (13 February 2019). "The Bizarre Planets That Could Be Humanity's New Homes". The Atlantic. Retrieved 10 February 2021.
    10. ↑ "HEC: Exoplanets Calculator - Planetary Habitability Laboratory @ UPR Arecibo". Archived from the original on 5 September 2019. Retrieved 8 February 2018.
    11. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today . Retrieved 19 February 2011.
    12. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
    13. ↑ 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.
    14. ↑ Gillon, M.; Triaud, A. H. M. J.; Demory, B.-O.; Jehin, E.; Agol, E.; Deck, K. M.; Lederer, S. M.; De Wit, J.; Burdanov, A.; Ingalls, J. G.; Bolmont, E.; Leconte, J.; Raymond, S. N.; Selsis, F.; Turbet, M.; Barkaoui, K.; Burgasser, A.; Burleigh, M. R.; Carey, S. J.; Chaushev, A.; Copperwheat, C. M.; Delrez, L.; Fernandes, C. S.; Holdsworth, D. L.; Kotze, E. J.; Van Grootel, V.; Almleaky, Y.; Benkhaldoun, Z.; Magain, P.; Queloz, D. (2017). "Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1" (PDF). Nature. 542 (7642): 456–460. arXiv: 1703.01424 . Bibcode:2017Natur.542..456G. doi:10.1038/nature21360. PMC   5330437 . PMID   28230125.
    15. ↑ "NASA telescope reveals largest batch of Earth-size, habitable-zone planets around single star". Exoplanet Exploration: Planets Beyond our Solar System (Press release). Retrieved 25 February 2017.
    16. ↑ Barr, Amy C.; Dobos, Vera; Kiss, László L. (2018). "Interior structures and tidal heating in the TRAPPIST-1 planets". Astronomy & Astrophysics. 613: A37. arXiv: 1712.05641 . Bibcode:2018A&A...613A..37B. doi:10.1051/0004-6361/201731992. S2CID   119516532.
    17. ↑ "AGO - Department of Astrophysics, Geophysics and Oceanography".
    18. 1 2 "Could these newly-discovered planets orbiting an ultracool dwarf host life?". The Guardian . 2 May 2016.
    19. ↑ "Three Potentially Habitable Worlds Found Around Nearby Ultracool Dwarf Star - Currently the best place to search for life beyond the Solar System". eso.org. Retrieved 2 May 2016.
    20. ↑ "Three New Planets Are the Best Bets for Life". Popular Mechanics. 2 May 2016. Retrieved 2 May 2016.
    21. ↑ Gillon, Michaël; Jehin, Emmanuël; et al. (2016). "Temperate Earth-sized planets transiting a nearby ultracool dwarf star". Nature . 533 (7602): 221–224. arXiv: 1605.07211 . Bibcode:2016Natur.533..221G. doi:10.1038/nature17448. PMC   5321506 . PMID   27135924.
    22. ↑ New Scientist. Exoplanet discovery
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