Global InformationExocomet information
(NASA; artist's conception).
An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987[1][2] around Beta Pictoris, a very young A-type main-sequence star. There are now (as of February 2019) a total of 27 stars around which exocomets have been observed or suspected.[3][4][5][6][7]
The majority of discovered exocometary systems (Beta Pictoris, HR 10,[8] 51 Ophiuchi, HR 2174,[9] HD 85905,[10] 49 Ceti, 5 Vulpeculae, 2 Andromedae, HD 21620, Rho Virginis, HD 145964,[11][12] HD 172555,[13] Lambda Geminorum, HD 58647, Phi Geminorum, Delta Corvi, HD 109573,[14] Phi Leonis,[15] 35 Aquilae,[16] HD 24966, HD 38056, HD 79469 and HD 225200[3]) are around very young A-type stars. The relatively old shell star Phi Leonis shows evidence of exocomets in the spectrum[15] and comet-like activity was detected around the old F2V-type star Eta Corvi.[4] In 2018 transiting exocomets were discovered around F-type stars, using data from the Kepler space telescope.[6] Some late B-type star (e.g. 51 Ophiuchi, HD 58647) are known to host exocomets.[14][9]
Observations of comets, and especially exocomets, improve our understanding of planet formation. Indeed, in the standard model of planet formation by accretion, planets are the result of the agglomeration of planetesimals, themselves formed by the coalescence of dust from the protoplanetary disk surrounding the star shortly after its formation. Thus, comets are the residuals of the volatile-rich planetesimals that remained in the planetary system without having been incorporated into the planets. They are considered fossil bodies that have seen the physical and chemical conditions prevailing at the time of planet formation.[citation needed]
Researching exocomets might provide answers to fundamental questions of the past of the solar system and the development of a life-supporting environment. Researchers can investigate the transport of water, cyanides, sulfides and pre-biotic molecules onto Earth-mass exoplanets with the help of exocomets.[17][18]
- ^ Ferlet, R.; Vidal-Madjar, A. & Hobbs, L. M. (1987). "The Beta Pictoris circumstellar disk. V – Time variations of the CA II-K line". Astronomy and Astrophysics. 185: 267–270. Bibcode:1987A&A...185..267F.
- ^ Beust, H.; Lagrange-Henri, A.M.; Vidal-Madjar, A.; Ferlet, R. (1990). "The Beta Pictoris circumstellar disk. X – Numerical simulations of infalling evaporating bodies". Astronomy and Astrophysics. 236: 202–216. Bibcode:1990A&A...236..202B.
- ^ a b Welsh, Barry Y.; Montgomery, Sharon L. (February 2018). "Further detections of exocomet absorbing gas around Southern hemisphere A-type stars with known debris discs". MNRAS. 474 (2): 1515–1525. Bibcode:2018MNRAS.474.1515W. doi:10.1093/mnras/stx2800. ISSN 0035-8711.
- ^ a b Welsh, Barry; Montgomery, Sharon L. (January 2019). "Comet-like activity in the circumstellar debris disk surrounding the 1.4 Gyr-old F2V star HD 109085". AAS. 233: 340.06. Bibcode:2019AAS...23334006W.
- ^ Boyajian, T. S.; et al. (April 2016). "Planet Hunters IX. KIC 8462852 – where's the flux?". Monthly Notices of the Royal Astronomical Society. 457 (4): 3988–4004. arXiv:1509.03622. Bibcode:2016MNRAS.457.3988B. doi:10.1093/mnras/stw218. S2CID 54859232.
- ^ a b Rappaport, S.; Vanderburg, A.; Jacobs, T.; LaCourse, D.; Jenkins, J.; Kraus, A.; Rizzuto, A.; Latham, D. W.; Bieryla, A.; Lazarevic, M.; Schmitt, A. (2018-02-21). "Likely transiting exocomets detected by Kepler". Monthly Notices of the Royal Astronomical Society. 474 (2): 1453–1468. arXiv:1708.06069. Bibcode:2018MNRAS.474.1453R. doi:10.1093/mnras/stx2735. ISSN 0035-8711. PMC 5943639. PMID 29755143.
- ^ Cite error: The named reference
:4was invoked but never defined (see the help page). - ^ Lagrange-Henri, A. M.; Beust, H.; Ferlet, R.; Vidal-Madjar, A. & Hobbs, L. M. (1990). "HR 10 – A new Beta Pictoris-like star?". Astronomy and Astrophysics. 227: L13–L16. Bibcode:1990A&A...227L..13L.
- ^ a b Lecavelier Des Etangs, A.; et al. (1997). "HST-GHRS observations of candidate β Pictoris-like circumstellar gaseous disks". Astronomy and Astrophysics. 325: 228–236. Bibcode:1997A&A...325..228L.
- ^ Welsh, B. Y.; Craig, N.; Crawford, I. A.; Price, R. J. (1998-10-01). "Beta Pic-like circumstellar disk gas surrounding HR 10 and HD 85905". Astronomy and Astrophysics. 338: 674–682. Bibcode:1998A&A...338..674W. ISSN 0004-6361.
- ^ Welsh, B. Y.; Montgomery, S. (2013). "Circumstellar Gas-Disk Variability Around A-Type Stars: The Detection of Exocomets?". Publications of the Astronomical Society of the Pacific. 125 (929): 759–774. Bibcode:2013PASP..125..759W. doi:10.1086/671757.
- ^ "'Exocomets' Common Across Milky Way Galaxy". Space.com. 7 January 2013. Archived from the original on 16 September 2014. Retrieved 8 January 2013.
- ^ Kiefer, F.; Lecavelier Des Etangs, A.; et al. (2014). "Exocomets in the circumstellar gas disk of HD 172555". Astronomy and Astrophysics. 561: L10. arXiv:1401.1365. Bibcode:2014A&A...561L..10K. doi:10.1051/0004-6361/201323128. S2CID 118533377.
- ^ a b Welsh, Barry Y.; Montgomery, Sharon L. (2015). "The Appearance and Disappearance of Exocomet Gas Absorption". Advances in Astronomy. 2015: 980323. Bibcode:2015AdAst2015E..26W. doi:10.1155/2015/980323.
- ^ a b Eiroa, C.; Rebollido, I.; Montesinos, B.; Villaver, E.; Absil, O.; Henning, Th; Bayo, A.; Canovas, H.; Carmona, A.; Chen, Ch; Ertel, S. (2016-10-01). "Exocomet signatures around the A-shell star φ Leonis?". Astronomy & Astrophysics. 594: L1. arXiv:1609.04263. Bibcode:2016A&A...594L...1E. doi:10.1051/0004-6361/201629514. ISSN 0004-6361. S2CID 41231308.
- ^ Montgomery, Sharon L.; Welsh, Barry Y. (2017-06-01). "Unusually high circumstellar absorption variability around the delta Scuti /lambda Boötis star HD 183324". Monthly Notices of the Royal Astronomical Society. 468 (1): L55–L58. Bibcode:2017MNRAS.468L..55M. doi:10.1093/mnrasl/slx016. ISSN 0035-8711.
- ^ Cuntz, Manfred; Loibnegger, Birgit; Dvorak, Rudolf (2018-11-30). "Exocomets in the 47 UMa System: Theoretical Simulations Including Water Transport". The Astronomical Journal. 156 (6): 290. arXiv:1811.09579. Bibcode:2018AJ....156..290C. doi:10.3847/1538-3881/aaeac7. ISSN 1538-3881. S2CID 118921188.
- ^ Matrà, Luca; Kral, Quentin; Su, Kate; Brandeker, Alexis; Dent, William; Gaspar, Andras; Kennedy, Grant; Marino, Sebastian; Öberg, Karin; Roberge, Aki; Wilner, David (2019-04-04). "Exocometary Science". Bulletin of the American Astronomical Society. 51 (3): 391. arXiv:1904.02715. Bibcode:2019BAAS...51c.391M.