SPECULOOS-3 b is an Earth-sized exoplanet, orbiting the ultracool red dwarf star SPECULOOS-3. It is relatively close to Earth, at a distance of 55 light-years.[4] SPECULOOS-3 b takes only about 17 hours to complete an orbit around SPECULOOS-3, and, because of that proximity, it receives very high levels of radiation and is tidally locked, meaning that one side of the planet always faces its host star.[5] Its discovery was made using the SPECULOOS project, and announced in May 2024 in the academic journal Nature Astronomy.[6]
 Artist's impression of SPECULOOS-3 b and its host star, a red dwarf much cooler, dimmer than smaller than the Sun. | |
| Discovery[1] | |
|---|---|
| Discovered by | Michael Gillon et al. |
| Discovery site | SPECULOOS |
| Discovery date | May 15, 2024 |
| Transit method[2] | |
| Designations | |
Named after | SPECULOOS |
| Orbital characteristics[1] | |
| 0.00733 AU | |
| 0.719 days (17 hours and 15 min.) | |
| Inclination | 89.44°±0.39° |
| Star | LSPM J2049+3336 (SPECULOOS-3) |
| Physical characteristics[1] | |
| 0.977±0.02 R🜨 0.07273 RJ | |
| Mass | 0.894 M🜨 (estimate)[3] |
| Temperature | 553±8 K (280±8 °C) |
The host star of SPECULOOS-3 b is SPECULOOS-3 (LSPM J2049+3336, TIC 230741378), an ultra-cool red dwarf star in the constellation Cygnus, with just one tenth of the Sun's mass, 13% of the size and 0.09% of its luminosity.[1]
Characteristics
editThe planet's radius, as deduced from its transit depth, is 0.98 R🜨, making it similar to Earth in size.[1] The mass of SPECULOOS-3b has been not measured,[1] but the NASA Exoplanet Catalog estimated it at 0.894 ME.[3] Measuring the planet's mass is essential to determining if it is rocky and to further contrain its composition.[1]
It orbits relatively close to its host star: one year on SPECULOOS-3 b is equivalent to about 17 hours in Earth.[4] The semi-major axis is equivalent to 0.7% of an astronomical unit.[1] As a consequence, the planet receives high levels of radiation from its host star,[5] and its planetary equilibrium temperature is estimated at 280°C assuming a null bond albedo, meaning that its dayside is likely made of solid rock.[1] It is also tidally locked to SPECULOOS-3, meaning that one side of the planet is always facing the star, while the other side is always facing away.[4][5][6]
Due to the planet's high temperature and its host star's infrared brightness, its dayside's astronomic spectrum (of emission) might be measured by the MIRI/RLS instrument aboard the James Webb Space Telescope. Such observations should reveal the presence of an atmosphere around the planet, or constrain its mineralogical surface, if no gases are detected.[1]
Discovery
editThe discovery of SPECULOOS-3 b was made using the SPECULOOS project, led by the University of Liège, in Belgium, in collaboration with other universities across different countries.[6] SPECULOOS consists of a network of telescopes in search of faint stars and exoplanets around them.[5] The planet was discovered using the observatory in the Atacama Desert, Chile.[7]
The planet was detected using the transit method.[2] The host star SPECULOOS-3 was observed by the SAINT-EX telescope in 2021, for five nights, producing two light curves containing planetary transits. The star was later reviewed by the SPECULOOS-North observatory's Artemis telescope, revealing a clear transit-like signature on its light curve. Subsequent observations with the SAINT-EX and SPECULOOS-South telescopes revealed more planetary transits, which were associated with an Earth-like exoplanet transiting the star with an orbital period of 0.719 days.[1] SPECULOOS-3 b's discovery was announced in May 2024, in the journal Nature Astronomy.[6]
Host star
editLSPM J2049+3336, also known as SPECULOOS-3, is a red dwarf star (spectral type M6.5), 16.75 parsecs (54.6 ly) away[1] in the constellation Cygnus.[a] It is one of the smallest known stars, and is much cooler, dimmer and smaller than the Sun, having 0.1 times the mass, 0.08% the Sun's luminosity, and an effective temperature of 2,800 K (2,530 °C), which is less than half the Sun's temperature (5,772 K).[1] Its small radius of 0.12 R☉ make it the second-smallest star with a transiting planet, with only TRAPPIST-1 being smaller.[1]
Red dwarf stars such as SPECULOOS-3 are the most numerous type of stars, making up 70% of all stars in the Milky Way galaxy. They are expected to live 10 times more than the Sun, with lifespans longer than 100 billion years.[4]
Notes
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References
edit- ^ a b c d e f g h i j k l m n Gillon, Michaël; Pedersen, Peter P.; Rackham, Benjamin V.; Dransfield, Georgina; Ducrot, Elsa; Barkaoui, Khalid; Burdanov, Artem Y.; Schroffenegger, Urs; Gómez Maqueo Chew, Yilen; Lederer, Susan M.; Alonso, Roi; Burgasser, Adam J.; Howell, Steve B.; Narita, Norio; de Wit, Julien (2024-05-15). "Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3". Nature Astronomy. 8 (7): 865–878. arXiv:2406.00794. Bibcode:2024NatAs...8..865G. doi:10.1038/s41550-024-02271-2. ISSN 2397-3366.
- ^ a b "The Extrasolar Planet Encyclopaedia — SPECULOOS-3 b". Extrasolar Planets Encyclopaedia. Paris Observatory. Retrieved May 26, 2024.
- ^ a b "SPECULOOS-3 b - NASA Science". science.nasa.gov. Retrieved 2024-05-26.
- ^ a b c d "Discovery Alert: An Earth-sized World and Its Ultra-cool Star - NASA Science". science.nasa.gov. Retrieved 2024-05-26.
- ^ a b c d Hill, Samantha (2024-05-16). "Found: An Earth-sized exoplanet named SPECULOOS-3 b". Astronomy Magazine. Retrieved 2024-05-26.
- ^ a b c d "Astronomers discover new Earth-sized world orbiting an ultra-cool star". phys.org. May 15, 2024. Retrieved 2024-05-26.
- ^ "SPECULOOS-3b: A new frontier in the search for life on exoplanets". The Times of India. 2024-05-16. ISSN 0971-8257. Retrieved 2024-05-28.