TOI-2257 b

Last updated

TOI-2257 b
Discovery [1]
Discovered by Schanche et al.
Discovery dateNovember 2021
Transit
Orbital characteristics [1]
0.145±0.003  AU
Eccentricity 0.496+0.216
−0.133
35.189346(90)  d
Inclination 89.786°+0.078°
−0.062°
Star TOI-2257
Physical characteristics [1]
Mean radius
2.194+0.113
−0.111  R🜨
Mass 5.712+4.288
−2.311  M🜨 (predicted)
Temperature 256+61
−17  K (−17 °C; 1 °F, equilibrium)

    TOI-2257 b is an extremely eccentric (0.496) [2] 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. [3] As a small planet in the habitable zone, it is included in the Planetary Habitability Laboratory's list of potentially habitable exoplanets. [4]

    Contents

    Discovery

    The planet was discovered using the transit method, by TESS in November 2021. It has one of the longest orbital periods of any TESS planet. Further observations intend to find possible water vapor in the atmosphere of the planet, as well as any other planets in the system if they exist. The planet is most likely not a false positive, and its existence is supported by photometry and the high-resolution observations of ground-based telescopes. [3]

    Properties

    Mass, radius, and temperature

    The planet has a radius 2.19 times that of Earth. Its mass and density are unknown, although it is predicted to have a mass roughly 3.4-10 times that of Earth based on mass-radius relationships. [1] Based on its size, it is likely a Neptune-like world. Its average equilibrium temperature is 256 K (−17 °C; 1 °F), similar to the average temperature of Alert, Canada on Earth, and varies from approximately 193 K (−80 °C; −112 °F) during aphelion to 373 K (100 °C; 212 °F) at perihelion. [3] [5] However, the actual temperature could differ and would also vary throughout the planet's eccentric orbit. [2]

    Orbit

    The planet has an orbital period of 35.19 days, with an extremely high eccentricity of almost 0.5. [3] It has a semimajor axis of 0.145 AU, approximately half of Mercury's at the point in its orbit nearest to the Sun. [2] According to NASA Exoplanet Exploration, the planet's eccentric orbit takes it through the "too hot" zone (albeit for a very short amount of time), then out to the outer fringes of the habitable zone, near the border with the "too cold" zone. [6]

    The planet has the highest eccentricity ever recorded around an M-type star, and the third highest of any known mini-Neptune as of 2021. [7]

    Star

    The planet's star is M3V, with a temperature of 3,430 K. It has a metallicity of -0.27 and is about 8 billion years old, with ~0.3 times the mass and 0.33 times the radius of the Sun. [3] [2] For comparison, the Sun has a temperature of 5,778 K and is 4,572,000,000 years old, with a spectral class of G2V. The metallicity is 0.00.

    Habitability

    The planet gets 37/50ths of the light that Earth gets from the Sun, putting it well within the habitable zone. However, the planet is likely a mini-Neptune given its size. The planet has an ESI of 0.72, similar to that of Mars and Kepler-22b. [3] [4] The equilibrium temperature could range from a comfortable 317 K (44 °C; 111 °F) to a chilly 239 K (−34 °C; −29 °F), both within the thermal amplitude of the Earth. [2] With a greenhouse effect similar in intensity to Earth's, the temperature would be around 289 K (16 °C; 61 °F), and with a greenhouse effect twice as strong as Earth's, 322 K (49 °C; 120 °F). [8] The temperature would vary throughout the planet's eccentric orbit. Due to the planet's habitable-zone location, water vapor is possible in the atmosphere. More detailed characterizations of the planet's atmosphere, including determining whether water vapor is present are expected from the JWST. [3] [7]

    Tidal locking

    Due to the planet's distance from its star, it would likely be tidally locked, with one side always facing the star, if it had a near-circular orbit. Due to its eccentric orbit, it is likely in a spin-orbit resonance instead. [9]

    Eccentricity

    The planet has an extremely high eccentricity, which could, perhaps, play a part in its habitability. The planet, due to its high eccentricity, could go through frigid winters and sweltering summers. This could compromise its habitability by setting off a runaway greenhouse effect if a long period of time is spent above 320 K (47 °C) or 117 °F, or a runaway glaciation effect if a long period of time is spent far below 273 K (0 °C) or 32 °F. This would cause most or all of the planet to become uninhabitable, regardless of atmospheric conditions that combat tidal locking. [10] On the other hand, the planet's eccentricity could be a factor working against tidal locking in and of itself; the planet would settle into a 3:2 resonance, where the year is 1.5 times as long as the day. Models show that such a planet, if oceanic, would have open water in the lower and middle latitudes and water ice above 60 °N/below 60 °S, much like on our Earth. This model is known as the "striped-ball planet". [11]

    In this model, there are four temperature tiers, with the warmest ocean temperatures occurring between 21 °N and °S, the next warmest between 21 and 46° on both sides of the equator, the second coldest between 46 and 62°, and the coldest, cold enough to form sea ice, between 61° and the poles. The freezing temperature of ocean water is assumed to be −1.8 °C (28.8 °F). [11]

    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, panthalassic planet, maritime world, water world or aquaplanet, 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">Gliese 581c</span> Super-Earth exoplanet orbiting Gliese 581

    Gliese 581c is an exoplanet orbiting within the Gliese 581 system. It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.5 times that of the Earth, it is classified as a super-Earth.

    <span class="mw-page-title-main">Super-Earth</span> Planet with a mass between Earth and Uranus

    A Super-Earth is a type of exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.

    This page describes exoplanet orbital and physical parameters.

    <span class="mw-page-title-main">Discoveries of exoplanets</span> Detecting planets located outside the Solar System

    An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 1 January 2024, there are 5,576 confirmed exoplanets in 4,113 planetary systems, with 887 systems having more than one planet. This is a list of the most notable discoveries.

    <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">Kepler-22b</span> Super-Earth exoplanet orbiting Kepler-22

    Kepler-22b is an exoplanet orbiting within the habitable zone of the Sun-like star Kepler-22. It is located about 640 light-years from Earth in the constellation of Cygnus. It was discovered by NASA's Kepler Space Telescope in December 2011 and was the first known transiting planet to orbit within the habitable zone of a Sun-like star, where liquid water could exist on the planet's surface. Kepler-22 is too dim to be seen with the naked eye.

    Kepler-61b is a super-Earth exoplanet orbiting within parts of the habitable zone of the K-type main-sequence star Kepler-61. It is located about 1,100 light-years from Earth in the constellation of Cygnus. It was discovered in 2013 using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured, by NASA's Kepler spacecraft.

    <span class="mw-page-title-main">Kepler-442b</span> Super-Earth orbiting Kepler-442

    Kepler-442b is a confirmed near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the K-type main-sequence star Kepler-442, about 1,206 light-years (370 pc) from Earth in the constellation of Lyra.

    Kepler-296e is a confirmed super-Earth exoplanet orbiting within the habitable zone of Kepler-296. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the discovery of the exoplanet on 26 February 2014.

    <span class="mw-page-title-main">K2-3d</span> Mini-Neptune orbiting K2-3

    K2-3d, also known as EPIC 201367065 d, is a confirmed exoplanet of probable mini-Neptune type orbiting the red dwarf star K2-3, and the outermost of three such planets discovered in the system. It is located 143 light-years away from Earth in the constellation of Leo. 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 the first planet in the Kepler "Second Light" mission to receive the letter "d" designation for a planet. Its discovery was announced in January 2015.

    HD 219134 g, also known as HR 8832 g, is an unconfirmed exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. It has a minimum mass of 11 or 15 Earth masses, suggesting that it is likely a Neptune-like ice giant. Unlike HD 219134 b and HD 219134 c it is not observed to transit and thus its radius and density are unknown. If it has an Earth-like composition, it would have a radius 1.9 times that of Earth. However, since it is probably a Neptune-like planet, it is likely larger.

    Wolf 1061d is an exoplanet orbiting the red dwarf star Wolf 1061 in the Ophiuchus constellation, about 13.8 light years from Earth. It is the third and furthest planet in order from its host star in a triple planetary system, and has an orbital period of about 217 days.

    <span class="mw-page-title-main">LHS 1140 b</span> Super-Earth orbiting LHS 1140

    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, 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, or a dense mini-Neptune. LHS 1140 b orbits entirely within the star's habitable zone and gets 43% the incident flux of Earth. 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.

    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.

    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).

    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">Hycean planet</span> Water-covered planet with a hydrogen-rich atmosphere

    A hycean planet is a particular type of exoplanet that features a liquid water ocean under a hydrogen-rich atmosphere.

    <span class="mw-page-title-main">K2-332 b</span> Potentially habitable exoplanet

    K2-332 b is a potentially habitable Super-Earth or Mini-Neptune exoplanet with a radius of 2.2 earths. It is in the empirical habitable zone, receiving 1.17 times the light that Earth gets from the sun. Its star, K2-332, is type M4V, with a temperature of ~3300 K. It was detected using the transit method in 2016 and is 402 light-years away.

    References

    1. 1 2 3 4 Schanche, N.; Pozuelos, F. J.; et al. (January 2022). "TOI-2257 b: A highly eccentric long-period sub-Neptune transiting a nearby M dwarf". Astronomy & Astrophysics . 657: A45. arXiv: 2111.01749 . Bibcode:2022A&A...657A..45S. doi:10.1051/0004-6361/202142280. S2CID   240419956.
    2. 1 2 3 4 5 "TOI-2257 | NASA Exoplanet Archive". exoplanetarchive.ipac.caltech.edu. Retrieved November 17, 2023.
    3. 1 2 3 4 5 6 7 Nowakowski, Tomasz; Phys.org. "Astronomers discover a sub-Neptune exoplanet orbiting nearby star". phys.org. Retrieved November 17, 2023.
    4. 1 2 "PHL @ UPR Arecibo - The Habitable Exoplanets Catalog". phl.upr.edu. Retrieved November 17, 2023.
    5. ↑ Bern, University of (January 9, 2022). "Eccentric Exoplanet Discovered: Sub-Neptune Planet Orbiting in "Habitable Zone" of Red Dwarf Star". SciTechDaily. Retrieved November 20, 2023.
    6. ↑ "Exoplanet-catalog". Exoplanet Exploration: Planets Beyond our Solar System. Retrieved November 19, 2023.
    7. 1 2 Lea, Robert (November 15, 2021). "Astronomers Find Sub-Neptune Planet That May Have Liquid Water". Newsweek. Retrieved November 20, 2023.
    8. ↑ "Greenhouse effects... also on other planets". www.esa.int. Retrieved November 17, 2023.
    9. ↑ Hasler, Caroline (February 17, 2022). "Tidally Locked and Loaded with Questions". Eos. Retrieved November 17, 2023.
    10. ↑ "Obliquity and eccentricity determine exoplanet habitability". www.earthmagazine.org. Retrieved November 17, 2023.
    11. 1 2 Wang, Yuwei; Tian, Feng; Hu, Yongyun (July 2014). "Climate Patterns of Habitable Exoplanets in Eccentric Orbits Around M Dwarfs". The Astrophysical Journal Letters. 791 (1): L12. Bibcode:2014ApJ...791L..12W. doi: 10.1088/2041-8205/791/1/L12 . ISSN   2041-8205.
    12. ↑ "NASA's Hubble Finds Water Vapor on Habitable-Zone Exoplanet for 1st Time - NASA Science". science.nasa.gov. Retrieved November 20, 2023.
    13. ↑ Diamond-Lowe, Hannah; Kreidberg, Laura; Harman, C. E.; Kempton, Eliza M.-R.; Rogers, Leslie A.; Joyce, Simon R. G.; Eastman, Jason D.; King, George W.; Kopparapu, Ravi; Youngblood, Allison; Kosiarek, Molly R.; Livingston, John H.; Hardegree-Ullman, Kevin K.; Crossfield, Ian J. M. (October 2022). "The K2-3 System Revisited: Testing Photoevaporation and Core-powered Mass Loss with Three Small Planets Spanning the Radius Valley". The Astronomical Journal. 164 (5): 172. arXiv: 2207.12755 . Bibcode:2022AJ....164..172D. doi: 10.3847/1538-3881/ac7807 . ISSN   1538-3881.
    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.