WD 0806-661 B,formally namedAhra,is a planetary-mass companion of thewhite dwarfstarWD 0806−661,or Maru.
 JWST image of WD 0806−661 B and its white dwarf star | |
| Discovery[1] | |
|---|---|
| Discovered by | Luhman et al. |
| Discovery date | 2011 |
| Direct imaging | |
| Designations | |
| Ahra, GJ 3483 B | |
| Orbital characteristics | |
| 2,500 AU | |
| Star | WD 0806−661 |
| Physical characteristics | |
| 1.12RJ | |
| Mass | 7-9MJ |
| 16.17 g (Estimate) | |
| Temperature | 325-350 K |
This object was discovered in 2011 by theSpitzer Space Telescope.It has a mass of between 7-9MJ,putting it as a gas giant planet. At the time of its discovery, WD 0806-661 b was the coldest brown dwarf ever discovered, with a temperature of 325-350 Kelvin (52-77 °C or 125-170 °F)[2]and also had the largest separation from its star at about 2,500AUat the time of its discovery. The photometric colors of the object suggest it is metal-poor.[3]
As of 2021, WD 0806-661 b is a potential target for study from theJames Webb Space Telescope.[4]
Host star
editWD 0806−661, or Maru, is awhite dwarfstar of the spectral type DQ. The metal-poor composition of its planetary-mass companion could explain its spectral type, as it is theorized that hydrogen-deficient stars of theasymptotic giant branchcould evolve into white dwarfs of spectral type DB and then DQ as they cool down.[5]WD 0806-661 is estimated to be 1.5-2.7 billion years old,[6]and likely used to be anA-type main sequence starof 2.1 ± 0.3solar massesbefore reaching the end of its life and becoming a white dwarf.[7]WD 0806-661 B may have formed closer to the star, but migrated further away as it reached the end of its life.
Characteristics
editBecause it orbits very far away from its star, WD 0806−661 B is likely very dark, receiving almost no light from its star. However, due to the object's high mass, internal heat keeps the temperature hotter than that of Earth.[2]The object's radius is estimated to be 12% larger than that of Jupiter,[8]and is likely the same age as the star. Despite having temperatures comparable to that of Earth, WD 0806−661 B is a poor candidate for extraterrestrial life due to high surface gravity and lack of starlight. Because of its large mass and distance from its star, WD 0806−661 B could host many largeexomoons.
The WD 0806−661 system is planned to be studied by theJames Webb Space Telescope,which will probe theatmosphereof the object, as well as search for other planetary-mass bodies in the system.
Type of object
editThere is no consensus as to whether WD 0806-661 b should be considered anexoplanetor asub-brown dwarf.Based on its large distance from the white dwarf, this object likely formed like a star rather than in aprotoplanetary disk,and it is generally described as a brown dwarf in the scientific literature.[9]However, theIAUconsiders objects below the~13MJlimiting mass fordeuterium fusionthat orbit stars (or stellar remnants) to be planets, no matter how they formed.[10]Additionally, WD 0806-661 b has been named Ahra through the IAU'sNameExoWorldsexoplanet naming campaign,[11]and is included in databases such as theNASA Exoplanet Archive.[12]
See also
edit- WD 0806−661
- COCONUTS-2b- Another planetary-mass companion with a large separation from its star
- List of Y-dwarfs
References
edit- ^Luhman, K. L.; Burgasser, A. J.; Bochanski, J. J. (March 2011)."Discovery of a Candidate for the Coolest Known Brown Dwarf".The Astrophysical Journal Letters.730(1): L9.arXiv:1102.5411.Bibcode:2011ApJ...730L...9L.doi:10.1088/2041-8205/730/1/L9.ISSN2041-8205.
- ^abLeggett, S. K.; Tremblin, P.; Esplin, T. L.; Luhman, K. L.; Morley, Caroline V. (2017-06-21)."The Y-Type Brown Dwarfs: Estimates of Mass and Age from New Astrometry, Homogenized Photometry and Near-Infrared Spectroscopy".The Astrophysical Journal.842(2): 118.arXiv:1704.03573.doi:10.3847/1538-4357/aa6fb5.ISSN1538-4357.
- ^"_13428"._13428.doi:10.5270/esa-4bo1j7l.Retrieved2023-09-09.
- ^"1276 - Spectroscopic Observations of WD 0806-661B"(PDF).
- ^Camisassa, María E.; Althaus, Leandro G.; Rohrmann, René D.; García-Berro, Enrique; Torres, Santiago; Córsico, Alejandro H.; Wachlin, Felipe C. (April 2017)."Updated Evolutionary Sequences for Hydrogen-deficient White Dwarfs".The Astrophysical Journal.839(1): 11.doi:10.3847/1538-4357/aa6797.hdl:11336/63304.ISSN0004-637X.
- ^"The Extrasolar Planet Encyclopaedia — WD 0806-661 B b".Extrasolar Planets Encyclopaedia.Retrieved2023-09-09.
- ^Luhman, Kevin; Burgasser, Adam; Bochanski, John (2011-01-01)."Confirmation of a Candidate for the Coolest Known Brown Dwarf".Spitzer Proposal:70203.Bibcode:2011sptz.prop70203L.
- ^"Exoplanet-catalog".Exoplanet Exploration: Planets Beyond our Solar System.Retrieved2023-09-09.
- ^Rodriguez, David R.; Zuckerman, B.; Melis, Carl; Song, Inseok (May 2011). "The Ultra Cool Brown Dwarf Companion of WD 0806-661B: Age, Mass, and Formation Mechanism".The Astrophysical Journal Letters.732(2): L29.arXiv:1103.3544.Bibcode:2011ApJ...732L..29R.doi:10.1088/2041-8205/732/2/L29.
- ^Lecavelier des Etangs, A.; Lissauer, Jack J. (June 2022). "The IAU working definition of an exoplanet".New Astronomy Reviews.94:101641.arXiv:2203.09520.Bibcode:2022NewAR..9401641L.doi:10.1016/j.newar.2022.101641.IAU website link
- ^"2022 Approved Names".nameexoworlds.iau.org.IAU.Retrieved7 June2023.
- ^"WD 0806-661".NASA Exoplanet Archive.Retrieved22 January2024.