Astronomy:COCONUTS-2b
 COCONUTS-2b with unWISE. The planet in the center of the image stands out due to its red color. The host star is not pictured here. | |
| Discovery | |
|---|---|
| Discovered by | Zhoujian Zhang Michael Liu Zach Claytor William Best Trent Dupuy Robert Siverd[1] |
| Discovery date | August 2011[2] July 2021[3] |
| Direct imaging | |
| Designations | |
| WISEPA J075108.79-763449.6[2] | |
| Orbital characteristics | |
| 7,506.0 AU (1.12288×1012 km)[4] or ~0.1185 ly (~0.03633 pc) | |
| Orbital period | 1101369.9 years[4] |
| Star | L 34-26 |
| Physical characteristics | |
| Mean radius | 1.12±0.04 |♃|J}}}}}}[5] |
| Mass | 6.3+1.5 −1.9 |♃|J}}}}}}[6][4] |
| 4.11+0.11 −0.18 dex[6] | |
| Physics | 434 ± 9 K[6] |
Spectral type | T9 |
COCONUTS-2 b, or WISEPA J075108.79-763449.6, is a gas giant exoplanet that orbits the M-type star L 34-26. With a mass of 6.3 Jupiters, it takes over one million years to complete one orbit around the star, and it is 7,506 AU away from it.[1]
The planet was discovered in 2011 and was initially identified as a T9 free-floating brown dwarf WISEPA J075108.79−763449.6.[2] During the COol Companions ON Ultrawide orbiTS (COCONUTS) survey, its association with L 34-26 was announced in 2021.[7] At a distance of 10.9 pc, COCONUTS-2b is the closest directly imaged exoplanet to Earth known to date.[8]
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]
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 Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Chamaeleon |
| Right ascension | 07h 49m 12.71s |
| Declination | +76° 42′ 02.5″ |
| Apparent magnitude (V) | 11.3[10] |
| Characteristics | |
| Evolutionary stage | Red dwarf |
| Spectral type | M3V[11] |
| Astrometry | |
| Radial velocity (Rv) | 1.19[12] km/s |
| Proper motion (μ) | RA: -102.154[12] mas/yr Dec.: -192.918[12] mas/yr |
| Parallax (π) | 91.8263[12] mas |
| Distance | 35.5±0.0065[6] ly (10.89±0.002 pc) |
| Details | |
| Mass | 0.37±0.02[6] M☉ |
| Radius | 0.388±0.11[6] R☉ |
| Temperature | 3,406±69[6] K |
| Age | 475±325[6] 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.[13]
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.[14]
Gallery
The COCONUTS-2 system with unWISE
The planet COCONUTS-2b with Gemini-South
Allwise image by the discoverers, showing planet COCONUTS-2b
References
- ↑ 1.0 1.1 "Massive COCONUTS exoplanet discovery led by UH grad student | University of Hawaiʻi System News". University of Hawaiʻi News (University of Hawaiʻi at Mānoa). https://www.hawaii.edu/news/2021/07/27/massive-coconuts-exoplanet-discovery-uh-grad-student/.
- ↑ 2.0 2.1 2.2 2.3 Kirkpatrick, J. Davy; Cushing, Michael C.; Gelino, Christopher R.; Griffith, Roger L.; Skrutskie, Michael F.; Marsh, Kenneth A.; Wright, Edward L.; Mainzer, A. et al. (2011-12-01). "The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE)". The Astrophysical Journal Supplement Series 197 (2): 19. doi:10.1088/0067-0049/197/2/19. ISSN 0067-0049. Bibcode: 2011ApJS..197...19K. https://ui.adsabs.harvard.edu/abs/2011ApJS..197...19K.
- ↑ 3.0 3.1 Kooser, Amanda. "Massive exoplanet 'Coconuts-2b' could help reveal the secrets of young gas giants" (in en). CNET. https://www.cnet.com/news/meet-coconuts-2b-an-exoplanet-with-six-times-the-mass-of-jupiter/.
- ↑ 4.0 4.1 4.2 "COCONUTS-2 b". National Aeronautics and Space Administration. https://exoplanets.nasa.gov/exoplanet-catalog/7945/coconuts-2-b/.
- ↑ "COCONUTS-2". Open Exoplanet Catalogue. http://www.openexoplanetcatalogue.com/planet/COCONUTS-2%20b/.
- ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 Zhang, Zhoujian; Liu, Michael C.; Claytor, Zachary R.; Best, William M. J.; Dupuy, Trent J.; Siverd, Robert J. (2021-08-01). "The Second Discovery from the COCONUTS Program: A Cold Wide-orbit Exoplanet around a Young Field M Dwarf at 10.9 pc". The Astrophysical Journal 916 (2): L11. doi:10.3847/2041-8213/ac1123. ISSN 0004-637X. Bibcode: 2021ApJ...916L..11Z.
- ↑ "Exoplanet-catalog". https://exoplanets.nasa.gov/exoplanet-catalog/7945/coconuts-2-b/.
- ↑ Siegel, Ethan. "Astronomers Go Nuts For Closest Exoplanet Directly Imaged Ever: COCONUTS-2b" (in en). https://www.forbes.com/sites/startswithabang/2021/08/02/astronomers-go-nuts-for-closest-exoplanet-directly-imaged-ever-coconuts-2b/.
- ↑ Marley, Mark S.; Fortney, Jonathan J.; Hubickyj, Olenka; Bodenheimer, Peter; Lissauer, Jack J. (2007-01-01). "On the Luminosity of Young Jupiters". The Astrophysical Journal 655 (1): 541–549. doi:10.1086/509759. ISSN 0004-637X. Bibcode: 2007ApJ...655..541M.
- ↑ Martin, Pierre-Yves (2021). "Planet COCONUTS-2 b" (in en). Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/coconuts_2_b--7920/.
- ↑ Martin, Pierre-Yves (2021). "Planet COCONUTS-2 b" (in en). Extrasolar Planets Encyclopaedia. https://exoplanet.eu/catalog/coconuts_2_b--7920/.
- ↑ 12.0 12.1 12.2 "Simbad - Object view". https://simbad.cds.unistra.fr/mobile/object.html?object_name=COCONUTS-2A.
- ↑ "Giant Exoplanet Orbits Its Host Star Once Every 1.1 Million Years | Astronomy | Sci-News.com" (in en-US). http://www.sci-news.com/astronomy/coconuts-2b-exoplanet-09922.html.
- ↑ Stelzer, B.; Bogner, M.; Magaudda, E.; Raetz, St. (2022). "Flares and rotation of M dwarfs with habitable zones accessible to TESS planet detections". Astronomy and Astrophysics 665: A30. doi:10.1051/0004-6361/202142088. Bibcode: 2022A&A...665A..30S.
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