Fomalhaut b
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Exoplanet Fomalhaut b (Dagon) |
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| Hubble image of the formal skin system | |
| Constellation | Southern fish |
| Position equinox : J2000.0 |
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| Right ascension | 22h 57m 39.04625s |
| declination | −29 ° 37 ′ 20.0533 ″ |
| Orbit data | |
| Central star | Fomal skin |
| Major semi-axis | 115 AU |
| eccentricity | 0.11 |
| Period of circulation | 320000 d |
| Further data | |
| Dimensions | 3 +0−3 M J |
| distance | 7.7 pc |
| method | Imaging |
| history | |
| Date of discovery | 2008 |
Fomalhaut b ( Dagon ) is an object about 25 light-years away that orbits the star Fomalhaut in the constellation of the Southern Pisces.
If it were an exoplanet , it would be the first to be detected directly in optically visible light. Almost at the same time, however, a planetary system was discovered in infrared light around HR 8799 . Several objects were previously discovered in infrared light, but have not been detected in the optically visible, nor are they in a multiplanet system.
In April 2020 research results were presented according to which the object could not be a larger planet but a cloud of dust as a result of a collision between two smaller bodies about 200 km in diameter. Something similar was already seen as possible in 2012.
discovery
The main sequence star Fomalhaut of spectral class A has been a target of the search for planetary systems since the IRAS satellite discovered an extensive ring of dust around it (similar to the Kuiper belt ) in the 1980s . In 2004, observations from the Hubble Space Telescope revealed that this disk of dust has a sharp inner boundary. The assumption was that a massive planet would have to influence the dust disk gravitationally. Another clue arose from the fact that the dust disc is elliptical and not exactly centered on the star.
Since 2001, Fomalhaut has been observed by a research group led by Paul Kalas from the University of California, Berkeley . Repeated Hubble recordings between 2004 and 2006 showed a point of light within the dust ring, which evidently moves on a Keplerian orbit around Fomalhaut. The discovery was published in November 2008. This was the first direct visual evidence for the existence of exoplanets.
In 2010 the system was photographed again by the Hubble telescope. In the new photo, Fomalhaut b deviates from its previously calculated path. This led skeptics to question the existence of Fomalhaut b. However, the deviations could also be explained by the use of a different camera.
Track properties
Orbit calculations based on observations made using the Hubble telescope in 2012 showed that Fomalhaut b orbits the central star on a far more eccentric orbit than previously assumed. The distance fluctuates between 49 AU and 290 AU with a period of about 2000 years.
Physical Properties
The physical properties of Fomalhaut b can only be extrapolated from the orbit parameters . The calculations assume that Fomalhaut b (if it is actually an exoplanet) can be a maximum of about three times as massive as Jupiter , otherwise it would destroy the dust disk. The probable mass of such a planet would be between half and twice the mass of Jupiter ; its radius would in any case correspond approximately to that of Jupiter.
The surface temperature of such a planet should roughly correspond to that of Neptune (−200 ° C), since the higher luminosity of Fomalhaut compensates for the distance. When it was discovered, the object appeared a billion times fainter than Fomalhaut. This is still much brighter than the surface of the planet alone would suggest. One possible explanation is that Fomalhaut b is surrounded by a huge ring system of ice and dust, which should correspond to the dimensions of the orbits of the Galilean moons around Jupiter.
Proper name
As with all exoplanets, the systematic name results from the name of the star and a lowercase letter added according to the sequence in which it was discovered. After a publicly advertised competition by the International Astronomical Union (IAU), Fomalhaut b also received the proper name Dagon on December 15, 2015 , which goes back to the deity Dagān .
Web links
- Hubble Space Telescope Directly Observes Exoplanet - Video about the discovery by the Hubble Telescope
- Exoplanet is heading for the debris zone. Spiegel Online , January 9, 2013, accessed April 21, 2020 .
Individual evidence
- ↑ Simbad
- ↑ a b c d e f Exoplanet.eu
- ^ András Gáspár, George H. Rieke: New HST data and modeling reveal a massive planetesimal collision around Fomalhaut. PNAS , April 20, 2020, accessed April 21, 2020 . doi : 10.1073 / pnas.1912506117 - arxiv : 2004.08736 dated April 21, 2020 and a note that this is not the original PNAS article.
- ↑ Martin Holland: Exoplanet disappeared: Fomalhaut b was probably a gigantic cloud of debris. Heise online , April 21, 2020, accessed on April 22, 2020 .
- ↑ Raphael Galicher, Christian Marois, B. Zuckerman, Bruce Macintosh: Fomalhaut b: Independent Analysis of the HubbleSpace Telescope Public Archive Data. In: The Astrophysical Journal , Volume 769, Number April 1 , 2013, accessed April 21, 2020 . doi : 10.1088 / 0004-637X / 769/1/42 , arxiv : 1210.6745v3
- ↑ Paul Kalas, James R. Graham & Mark Clampin: A planetary system as the origin of structure in Fomalhaut's dust belt ; Nature (2005), 435, pp. 1067-1070; doi : 10.1038 / nature03601 .
- ↑ astronomie-heute.de accessed on September 27, 2011
- ↑ JD Harrington and Ray Villard: NASA's Hubble Reveals Rogue Planetary Orbit for Fomalhaut B. NASA, January 8, 2013, accessed August 1, 2016 .
- Jump up ↑ Paul Kalas, James R. Graham, Eugene Chiang, Michael P. Fitzgerald, Mark Clampin, Edwin S. Kite, Karl Stapelfeldt, Christian Marois, John Krist: Optical Images of an Exosolar Planet 25 Light-Years from Earth ; Science (2008), Vol. 322, no. 5906, pp. 1345-1348; doi : 10.1126 / science.1166609 .
- ↑ Naming of exoplanets. International Astronomical Union (IAU), accessed April 22, 2020 .