LHS 1140 b

Last updated
LHS 1140 b
Artist's impression of the super-Earth exoplanet LHS 1140b.jpg
Artist's impression of the planet LHS 1140 b and its host star
Discovery [1]
Discovered by MEarth Project
Discovery date20 April 2017 (Published)
Transit
Orbital characteristics [2]
0.0946±0.0017  AU
Eccentricity <0.043
24.7369148±0.0000058  d [3]
Inclination 89.86°±0.04°
Star LHS 1140
Physical characteristics [2]
1.730±0.025  R🜨
Mass 5.60±0.19  M🜨
Mean density
5.9±0.3  g/cm3
Temperature 226±4  K (−47 °C; −53 °F, equilibrium)

    LHS 1140 b is an exoplanet orbiting within the conservative habitable zone of the red dwarf LHS 1140. Discovered in 2017 by the MEarth Project, [1] LHS 1140 b is about 5.6 times the mass of Earth and about 70% larger in radius, putting it within the super-Earth category of planets. It was initially thought to be a dense rocky planet, but refined measurements of its mass and radius have found a lower density, indicating that it is likely an ocean world with 9-19% of its mass composed of water. LHS 1140 b orbits entirely within the star's habitable zone and gets 43% the incident flux of Earth. [2] The planet is 49 light-years away and transits its star, making it an excellent candidate for atmospheric studies with ground-based and/or space telescopes. [1]

    Contents

    Host star

    LHS 1140 b orbits a small red dwarf, LHS 1140. It is 18.4% the mass and 21.6% the radius of the Sun with a spectral type of M4.5V. The temperature of LHS 1140 is 3,096  K (2,823  °C ; 5,113  °F ), and it has a luminosity of 0.0038 times that of the Sun. It is at least 5 billion years old. [2] For comparison, the Sun is 1 solar mass and radius, has a temperature of 5778 K with 1 solar luminosity, is 4.5 billion years old, and has the spectral type of G2V. In addition, LHS 1140 is a very inactive star, with no major flare events found by the discovery team of its planet. Unlike most stars its size, LHS 1140 has low amounts of activity and rotates every 130 days. [1]

    Characteristics

    Mass and radius

    LHS 1140 b has been detected using both the radial velocity method (which measures the mass of a companion object) and transit photometry (which determines radius). Because of this, LHS 1140 b is one of very few potentially habitable exoplanets with a determined mass and radius, the others all being those around TRAPPIST-1. The planet's radius is well-constrained at 1.730±0.025  R🜨 , equivalent to about 11,000 km. [2] Its radius is similar to that of Kepler-62e.

    A recent study from 2023 reevaluates the mass and radius of LHS 1140 b, finding a mass of 5.60±0.19 M🜨 and a radius of 1.730±0.025 R🜨, less massive and larger than previous estimates. This would make LHS 1140 b an ocean world or dense mini-Neptune rather than a terrestrial planet. [2]

    Orbit and temperature

    The orbit of LHS 1140 b takes 24.737 days to complete, much quicker than Earth's year of 365 days. Its orbital radius is at 0.0946 AU, or 9.46% the distance between Earth and the Sun. While this is quite close, the star LHS 1140 is so dim that the planet only gets 0.43 times the incident flux of Earth at this distance. [2] Assuming an albedo of 0, LHS 1140 b has an equilibrium temperature of 230 K (−43 °C; −46 °F), compared to Earth's at 255 K (−18 °C; −1 °F). If LHS 1140 b has an albedo similar to that of Earth, the equilibrium temperature would be even lower, at 201 K (−72 °C; −98 °F). However, with a greenhouse effect at least as strong as Earth's LHS 1140 b would have a surface temperature greater than 266 K (−7 °C; 19 °F) for an albedo of 0. Due to the high mass of the planet, it likely has a thicker atmosphere with a more powerful greenhouse effect. Like many potentially habitable planets around red dwarfs, the orbit of LHS 1140 b is quite circular: the eccentricity is measured to be lower than 0.29 to a 90% confidence. The circularization of the orbit cannot be explained by stellar tides, and thus the circularity of the orbit is likely to be natal. [1]

    Composition

    Initially the planet was believed to have an extremely high density around 12.5 g/cm3, one of the highest ever observed for a rocky planet and over twice the density of Earth, with an iron-nickel core taking up to 75% of the planet's total mass. [1] Later studies in 2018 and 2020 revised the planet's radius upwards, giving it a density of 7.82+0.98
    −0.88     g/cm3    , still consistent with a rocky composition, and a lower core mass fraction of 49±7%. [4] For comparison, Earth's core comprises about 32.5% of its mass. The 2020 study also suggests that about 4% of the planet's mass is composed of water, suggesting it could be an ocean world estimated to have an average ocean depth of 779±650 km. [4]

    A 2023 study measuring the planet's mass and radius with greater precision found a lower mass of about 5.6 times Earth's, and a correspondingly lower density, no longer consistent with a rocky planet given the planet's size. LHS 1140 b is likely an ocean world with an even greater water mass fraction of 9-19%, or a dense mini-Neptune. [2] JWST observations rule out a hydrogen-rich atmosphere, supporting the ocean world scenario. [5]

    Atmosphere

    A potential detection of water vapor in the atmosphere of LHS 1140 b was made in late 2020 with the Hubble Space Telescope, albeit at a low signal-to-noise ratio. [3] Observations by the James Webb Space Telescope (JWST) published in 2024 rule out a hydrogen-rich atmosphere and support a high mean molecular weight atmosphere, possibly consisting of nitrogen, water vapor, and carbon dioxide. [5] In July 2024, tentative hints of atmospheric nitrogen were detected by JWST, suggesting that the surface of planet might be mostly ice and partially covered in liquid water, which resembles an eyeball. If this detection could be verified, it would be the first evidence of a secondary atmosphere around a potentially habitable exoplanet. [6]

    Habitability

    LHS 1140 b orbits close to the outer edge of the habitable zone, a region around a star where temperatures are just right for liquid water to pool on the surface of orbiting planets, given sufficient atmospheric pressure. [7] The equilibrium temperature of LHS 1140 b is rather low, at 230 K (−43 °C; −46 °F), as cold as the polar regions on Earth. However, this is the calculated temperature excluding the impact of a thick atmosphere. With an Earth-like greenhouse effect, the surface temperature is about 266 K (−7 °C; 19 °F), but since the planet is so massive, the greenhouse effect may be even higher. At twice the greenhouse effect of Earth, LHS 1140 b would have a comfortable surface temperature of 296 K (23 °C; 73 °F). In addition, the host star is so inactive that atmospheric erosion will not be very high, suggesting the planet should be able to retain its atmosphere over long timescales. [1] If no atmosphere is present, LHS 1140 b is likely to be covered by a thin ice envelope. [8] In this case, it could receive enough radiogenic heating and tidal heating for significant amounts of liquid water to be transported through the ice shell to its surface via cryovolcanic venting of water-rich geysers. [8]

    See also

    Related Research Articles

    <span class="mw-page-title-main">Ocean world</span> Planet containing a significant amount of water or other liquid

    An ocean world, ocean planet or water world is a type of planet that contains a substantial amount of water in the form of oceans, as part of its hydrosphere, either beneath the surface, as subsurface oceans, or on the surface, potentially submerging all dry land. The term ocean world is also used sometimes for astronomical bodies with an ocean composed of a different fluid or thalassogen, such as lava, ammonia or hydrocarbons. The study of extraterrestrial oceans is referred to as planetary oceanography.

    <span class="mw-page-title-main">HD 85512 b</span> Terrestrial exoplanet orbiting HD 85512

    HD 85512 b is a currently-disputed exoplanet orbiting HD 85512, a K-type main-sequence star approximately 37 light-years from Earth in the constellation of Vela.

    <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">TRAPPIST-1d</span> Small Venus-like exoplanet orbiting TRAPPIST-1

    TRAPPIST-1d, is a small exoplanet, which orbits on the inner edge of the habitable zone of 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. 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. It receives just 4.3% more sunlight than Earth, placing it on the inner edge of the habitable zone. It has about <5% of its mass as a volatile layer, which could consist of atmosphere, oceans, and/or ice layers. A 2018 study by the University of Washington concluded that TRAPPIST-1d might be a Venus-like exoplanet with an uninhabitable atmosphere. The planet is an eyeball planet candidate.

    <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-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.

    <span class="mw-page-title-main">LHS 1140</span> Star in the constellation Cetus

    LHS 1140 is a red dwarf in the constellation of Cetus. Based on stellar parallax measurement, it is 48.8 light-years away from the Sun. 'LHS' refers to the Luyten Half-Second Catalogue of stars with proper motions exceeding half a second of arc annually. The star is over 5 billion years old and has only about 18% the mass of the Sun and 21% of its radius. LHS 1140's rotational period is 130 days. No flares have been observed.

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

    Ross 128 b is a confirmed Earth-sized exoplanet, likely rocky, that is orbiting within the inner habitable zone of the red dwarf star Ross 128, at a distance of around 11 light-years from Earth. The exoplanet was found using a decade's worth of radial velocity data using the European Southern Observatory's HARPS spectrograph at the La Silla Observatory in Chile. Ross 128 b is the nearest exoplanet around a quiet red dwarf, and is considered one of the best candidates for habitability. The planet is only 35% more massive than Earth, receives only 38% more starlight, and is expected to be a temperature suitable for liquid water to exist on the surface, if it has an atmosphere.

    Kepler-1652b is a super-Earth exoplanet, orbiting within the habitable zone of the red dwarf Kepler-1652 about 822 light-years away in the Cygnus constellation. Discovered by NASA's Kepler spacecraft, Kepler-1652b was first announced as a candidate in 2013, but wasn't validated until four years later in 2017. It is a potential super-Earth with 160% Earth's radius. The planet orbits well within the habitable zone of its system, the region where liquid water can exist on a planet's surface. The planet is an eyeball planet candidate.

    <span class="mw-page-title-main">K2-288Bb</span> Mini-Neptune orbiting K2-288B

    K2-288Bb is a super-Earth or mini-Neptune exoplanet orbiting in the habitable zone of K2-288B, a low-mass M-dwarf star in a binary star system in the constellation of Taurus about 226 light-years from Earth. It was discovered by citizen scientists while analysing data from the Kepler spacecraft's K2 mission, and was announced on 7 January 2019. K2-288 is the third transiting planet system identified by the Exoplanet Explorers program, after the six planets of K2-138 and the three planets of K2-233.

    TOI-700 is a red dwarf 101.4 light-years away from Earth located in the Dorado constellation that hosts TOI-700 d, the first Earth-sized exoplanet in the habitable zone discovered by the Transiting Exoplanet Survey Satellite (TESS).

    <span class="mw-page-title-main">TOI-700 d</span> Goldilocks terrestrial planet orbiting TOI-700

    TOI-700 d is a near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf TOI-700, the outermost planet within the system. It is located roughly 101.4 light-years (31.1 pc) away from Earth in the constellation of Dorado. The exoplanet is the first Earth-sized exoplanet in the habitable zone discovered by the Transiting Exoplanet Survey Satellite (TESS).

    <span class="mw-page-title-main">Kepler-1649c</span> Earth-size exoplanet orbiting Kepler-1649

    Kepler-1649c is an Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star Kepler-1649, the outermost planet of the planetary system discovered by Kepler’s space telescope. It is located about 301 light-years (92 pc) away from Earth, in the constellation of Cygnus.

    Kepler-737b is a super-Earth exoplanet 669 light years away. There is a chance it could be on the inner edge of the habitable zone.

    <span class="mw-page-title-main">K2-18b</span> Mini-Neptune orbiting the red dwarf K2-18

    K2-18b, also known as EPIC 201912552 b, is an exoplanet orbiting the red dwarf K2-18, located 124 light-years (38 pc) away from Earth. The planet is a sub-Neptune about 2.6 times the radius of Earth, with a 33-day orbit within the star's habitable zone. This means it receives about a similar amount of starlight as the Earth receives from the Sun. Initially discovered with the Kepler space telescope, it was later observed by the James Webb Space Telescope (JWST) in order to study the planet's atmosphere.

    TOI-2257 b is an extremely eccentric (0.496) exoplanet in or near the circumstellar habitable zone of the star TOI-2257, 188 light-years away. It is likely a sub-Neptune exoplanet, with a mass of 5.71 Mearth and a radius of 2.19 Rearth. As a small planet in the habitable zone, it is included in the Planetary Habitability Laboratory's list of potentially habitable exoplanets.

    References

    1. 1 2 3 4 5 6 7 Dittmann, Jason A.; Irwin, Jonathan M.; Charbonneau, David; Bonfils, Xavier; Astudillo-Defru, Nicola; Haywood, Raphaëlle D.; et al. (2017). "A temperate rocky super-Earth transiting a nearby cool star". Nature. 544 (7650): 333–336. arXiv: 1704.05556 . Bibcode:2017Natur.544..333D. doi:10.1038/nature22055. PMID   28426003. S2CID   2718408.
    2. 1 2 3 4 5 6 7 8 Cadieux, Charles; Plotnykov, Mykhaylo; et al. (January 2024). "New Mass and Radius Constraints on the LHS 1140 Planets: LHS 1140 b Is either a Temperate Mini-Neptune or a Water World". The Astrophysical Journal Letters . 960 (1): L3. arXiv: 2310.15490 . Bibcode:2024ApJ...960L...3C. doi: 10.3847/2041-8213/ad1691 .
    3. 1 2 Edwards, Billy; Changeat, Quentin; Mori, Mayuko; Anisman, Lara O.; Morvan, Mario; Yip, Kai Hou; Tsiaras, Angelos; Al-Refaie, Ahmed; Waldmann, Ingo; Tinetti, Giovanna (2020), "Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 B", The Astronomical Journal, 161 (1): 44, arXiv: 2011.08815 , Bibcode:2021AJ....161...44E, doi: 10.3847/1538-3881/abc6a5 , S2CID   226975730
    4. 1 2 Lillo-Box, J.; Figueira, P.; Leleu, A.; Acuña, L.; Faria, J. P.; Hara, N.; Santos, N. C.; Correia, A. C. M.; Robutel, P.; Deleuil, M.; Barrado, D.; Sousa, S.; Bonfils, X.; Mousis, O.; Almenara, J. M.; Astudillo-Defru, N.; Marcq, E.; Udry, S.; Lovis, C.; Pepe, F. (2020), "Planetary system LHS 1140 revisited with ESPRESSO and TESS", Astronomy & Astrophysics, 642: A121, arXiv: 2010.06928 , Bibcode:2020A&A...642A.121L, doi:10.1051/0004-6361/202038922, S2CID   222341356
    5. 1 2 Damiano, Mario; Bello-Arufe, Aaron; et al. (March 2024). "LHS 1140 b is a potentially habitable water world". arXiv: 2403.13265 [astro-ph.EP].
    6. ↑ "Habitable Zone Exoplanet LHS 1140b is Probably Snowball or Water World | Sci.News". Sci.News: Breaking Science News. 2024-07-09. Retrieved 2024-07-10.
    7. ↑ Hanks, Micah (2024-07-09). "Webb Telescope Reveals "Best Habitable Zone Exoplanet Currently Known," and It Could Be Home to Alien Life". The Debrief. Retrieved 2024-07-13.
    8. 1 2 Quick, Lynnae C.; Roberge, Aki; Tovar Mendoza, Guadalupe; Quintana, Elisa V.; Youngblood, Allison A. (2023-10-04). "Prospects for Cryovolcanic Activity on Cold Ocean Planets". The Astrophysical Journal. 956 (29): 29. Bibcode:2023ApJ...956...29Q. doi: 10.3847/1538-4357/ace9b6 .
    This page is based on this Wikipedia article
    Text is available under the CC BY-SA 4.0 license; additional terms may apply.
    Images, videos and audio are available under their respective licenses.