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Fomalhaut b
From Wikipedia, the free encyclopedia
| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
 |
||
| Parent star | ||
| Star | Fomalhaut | |
| Constellation | Piscis Austrinus | |
| Right ascension | (α) | 22h 57m 39.1s |
| Declination | (δ) | −29° 37′ 20″ |
| Apparent magnitude | (mV) | 1.16 |
| Distance | 25 ± 0.1 ly (7.66 ± 0.04 pc) |
|
| Spectral type | A3V | |
| Orbital elements | ||
| Semimajor axis | (a) | ~115 AU |
| Eccentricity | (e) | ~0.11 |
| Orbital period | (P) | ~872 y |
| Inclination | (i) | ~66° |
| Physical characteristics | ||
| Mass | (m) | 0.054 – 3 MJ |
| Discovery information | ||
| Discovery date | November 13, 2008 | |
| Discoverer(s) | Kalas et al. | |
| Detection method | Direct imaging | |
| Discovery site | Hubble Space Telescope | |
| Discovery status | Confirmed | |
| Other designations | ||
| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
Fomalhaut b is an extrasolar planet approximately 25 light-years away in the constellation of Piscis Austrinus.[2] The planet was discovered orbiting the A-type main sequence star Fomalhaut in 2008 in photos taken by the Hubble Space Telescope.[3] Fomalhaut b and three planets around HR 8799, whose discovery was announced simultaneously, were the first extrasolar planets whose orbital motion was confirmed via direct imaging.
Contents |
[edit] Discovery
The planet orbits Fomalhaut at a distance of approximately 115 AU (1.72×1010 km, 1.07×1010 mi), which is about 18 AU (2.7×109 km, 1.7×109 mi) closer to the star than the inner edge of the debris disk.[4] It was discovered after researchers spent eight years examining the system.[5]
The existence of the planet was inferred in 2005 from its influence on the Fomalhaut dust belt; the belt is not centered on the star, and has a sharper inner boundary than would normally be expected.[6][7] However, the planet was only located in May 2008 after Paul Kalas singled it out of Hubble photographs taken in 2004 and 2006.[5] NASA released the composite discovery photograph, obtained by the Hubble Space Telescope's ACS, on November 13, 2008. In the image, the bright outer oval band is the dust ring, while the features inside of this band represent noise from scattered starlight.[8]
Kalas remarked, "It’s a profound and overwhelming experience to lay eyes on a planet never before seen. I nearly had a heart attack at the end of May when I confirmed that Fomalhaut b orbits its parent star."[5]
Fomalhaut b is the first exoplanet observed directly in visible light, the first imaged planet since Neptune to have been predicted prior to discovery, and the first planet to have been correctly predicted based on its interaction with a debris disk.[9] It is also believed to be the coolest, lowest-mass object ever imaged outside our own solar system.[10]
[edit] Physical characteristics
The planet is estimated to be approximately the same size as Jupiter,[5] with a maximum mass of three Jupiters and a most probable mass of 0.5 to two.[7][11] It is 115 AU (17 billion km, 11 billion mi, about 20% greater than the aphelion distance of Eris and 3.8 times the semi-major axis of Neptune) from its sun, giving it an orbital period of 872 earth years.[5] Fomalhaut has about 16 times the Sun's luminosity, so Neptune and Fomalhaut b are in regions of similar temperature (due to the inverse square law).
Fomalhaut b is suspected, on the basis of its brightness in visible light and dimness in infrared, to be surrounded by a circumplanetary disc with a radius approximately 20–40 times the radius of Jupiter (by comparison, the outer edge of Saturn's A ring is at a distance of only about 2 Jupiter radii from the centre of the planet). This size is similar to the orbital radii of Jupiter's Galilean satellites and therefore may represent a stage in the formation of a system of moons around the planet.[5][7][3]
[edit] See also
[edit] References
- ^ NAME Fomalhaut b -- Extra-solar Planet Candidate, entry, SIMBAD. Accessed on line December 6, 2008.
- ^ Seth Borenstein (2008-11-14). "Images captured of 4 planets outside solar system". Associated Press via Google. Retrieved on 2008-11-14.
- ^ a b Kalas, Paul; Graham, James R.; Chiang, Eugene; Fitzgerald, Michael P.; Clampin, Mark; Kite, Edwin S.; Stapelfeldt, Karl; Marois, Christian; Krist, John (2008-11-13). "Optical Images of an Exosolar Planet 25 Light-Years from Earth". Science (AAAS). doi:. http://arxiv.org/abs/0811.1994. Retrieved on 20 November 2008.
- ^ "Science Centric". Retrieved on 2008-11-14.
- ^ a b c d e f Lewis Smith (2008-11-13). "First pictures taken of planet outside the solar system: Fomalhaut b". The Times. Retrieved on 2008-11-14.
- ^ Kalas, Paul; Graham, James R.; Clampin, Mark (2005). "A planetary system as the origin of structure in Fomalhaut's dust belt". Nature 435 (7045): 1067–1070. doi:. arΧiv:astro-ph/0506574.
- ^ a b c Alexander, Amir (2008-11-14). "Scientists Lay Eyes on Distant Planets". Planetary Society web site. Planetary Society. Retrieved on 2008-11-14.
- ^ "APOD: 2008 November 14 - Fomalhaut b". Retrieved on 2008-11-14.
- ^ Predictions for a planet just inside Fomalhaut's eccentric ring, Alice C. Quillen, Monthly Notices of the Royal Astronomical Society, 372, #1 (October 2006), pp. L14–L18, doi:10.1111/j.1745-3933.2006.00216.x, Bibcode: 2006MNRAS.372L..14Q.
- ^ "Exoplanets finally come into view". BBC. Retrieved on 2008-11-14.
- ^ Yeager, Ashley (2008-11-13). "Astronomers claim first snaps of planets beyond the Solar System". Nature News. Nature Publishing Group. doi:10.1038/news.2008.1224. Retrieved on 2008-11-16.