COCONUTS-2b
Discovery | |
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Discovered by | Zhoujian Zhang Michael Liu Zach Claytor William Best Trent Dupuy Robert Siverd[1] |
Discovery date | August 2011[2] July 2021 L 34-26 |
Physical characteristics | |
Mean radius | 1.12±0.04 RJ[5] |
Mass | 6.3+1.5 −1.9 MJ[6][4] |
4.11+0.11 −0.18 dex[6] | |
Temperature | 434 ± 9 K[6] |
Spectral type | T9 |
COCONUTS-2 b, or WISEPA J075108.79-763449.6, is a
The planet was discovered in 2011 and was initially identified as a T9 free-floating
Proposed formation scenarios
The researchers found that it is unlikely that COCONUTS-2b was formed inside the protoplanetary disk of the host star and it is more likely that the planet formed on its own via high entropy formation (aka hot-start process).[6][9]
The peculiar properties of COCONUTS-2b could be explained with different scenarios as proposed by Marocco et al. in 2024. The properties could be explained by a non-solar carbon-to-oxygen ratio, meaning that it formed inside a disk around L 34-26. In this scenario the most likely way COCONUTS-2b got in a higher orbit is by a stellar fly-by of two binaries or two planetary systems. In the second scenario L 34-26 is not actually young, but mimics youth due to tidal and/or magnetic interactions with an unseen companion. In this scenario COCONUTS-2b would be an old brown dwarf. In a third scenario COCONUTS-2b could be a captured old brown dwarf. This is however seen as unlikely due to the stellar fly-by requiring a low velocity.[10]
Atmosphere
The planet has a spectral type of T9, based on a low signal-to-noise near-infrared spectrum with Magellan/FIRE.[2][6] This spectral type suggests high amounts of methane, water vapor and low amounts of carbon monoxide in the atmosphere of COCONUTS-2b.
COCONUTS-2b might have both clouds and a non-equilibrium process in its atmosphere.[6]
Due to its large orbital separation, COCONUTS-2b is a great laboratory to study the atmosphere and composition of young gas-giant exoplanets.[3] Astronomers estimate the planet’s temperature to be around 434 K (161 °C; 322 °F).[6]
Host star
Observation data Epoch J2000.0 Equinox J2000.0 | |
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Constellation | Chamaeleon |
Right ascension | 07h 49m 12.71s |
Declination | +76° 42′ 02.5″ |
Apparent magnitude (V) | 11.3[11] |
Characteristics | |
Evolutionary stage | Red dwarf |
Spectral type | M3V[12] |
Details | |
Myr | |
Other designations | |
L 34-26, COCONUTS-2A, WISEPA J075108.79-763449.6, 1RXS J074912.9-764202, 2MASS J07491271-7642065, ASAS J074912-7641.9, Gaia DR1 5213167326052013184, Gaia DR2 5213167330349528064, Gaia DR3 5213167330349528064, NLTT 18592
PM J07492-7642,RAVE J074912.7-764207, TIC 272232401, TYC 9381-1809-1, UCAC4 067-006518, USNO-B1.0 0132-00043434 | |
Database references | |
SIMBAD | data |
L 34-26, also known as COCONUTS-2A and TYC 9381-1809-1, is a M3-type dwarf star located 35 light-years away, in the constellation of Chamaeleon. The star is about one-third the mass of the Sun, with an age between 150 and 800 million years old.[14]
Researchers using TESS found that L 34-26 showed stellar flares about every 0.48 days. It was the most active planet hosting star in their sample. The team studying the host star also found that L 34-26 is fast rotating with a rotation period of 2.83 days. The planet should not be influenced by the flares, because of the large orbital separation.[15] The star is seen almost equator-on with i = 81.8±5.8 deg and might belong to the proposed Ursa Major corona, which is 400 million years old.[10]
Gallery
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The COCONUTS-2 system with unWISE
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The planet COCONUTS-2b with Gemini-South
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Allwise image by the discoverers, showing planet COCONUTS-2b
References
- ^ a b "Massive COCONUTS exoplanet discovery led by UH grad student | University of Hawaiʻi System News". University of Hawaiʻi News. University of Hawaiʻi at Mānoa. Archived from the original on 15 December 2021. Retrieved 21 December 2021.
- ^ S2CID 16850733.
- ^ a b Kooser, Amanda. "Massive exoplanet 'Coconuts-2b' could help reveal the secrets of young gas giants". CNET. Archived from the original on 21 December 2021. Retrieved 21 December 2021.
- ^ National Aeronautics and Space Administration. Archivedfrom the original on 22 November 2021. Retrieved 21 December 2021.
- ^ "COCONUTS-2". Open Exoplanet Catalogue. Archived from the original on 21 December 2021. Retrieved 21 December 2021.
- ^ ISSN 0004-637X.
- ^ "Exoplanet-catalog". Exoplanet Exploration: Planets Beyond our Solar System. Archived from the original on 2021-11-22. Retrieved 2021-11-22.
- ^ Siegel, Ethan. "Astronomers Go Nuts For Closest Exoplanet Directly Imaged Ever: COCONUTS-2b". Forbes. Archived from the original on 2021-11-22. Retrieved 2021-11-22.
- S2CID 7793365.
- ^ arXiv:2404.14324.
- ^ Martin, Pierre-Yves (2021). "Planet COCONUTS-2 b". Extrasolar Planets Encyclopaedia. Retrieved 2023-11-28.
- ^ Martin, Pierre-Yves (2021). "Planet COCONUTS-2 b". Extrasolar Planets Encyclopaedia. Retrieved 2023-11-28.
- ^ a b c "Simbad - Object view". simbad.cds.unistra.fr. Retrieved 2023-11-28.
- ^ "Giant Exoplanet Orbits Its Host Star Once Every 1.1 Million Years | Astronomy | Sci-News.com". Breaking Science News | Sci-News.com. Archived from the original on 2021-11-22. Retrieved 2021-11-22.
- S2CID 249662585.