Fomalhaut b

Fomalhaut b is about 25 light years distant extrasolar planet orbiting the star Fomalhaut in the constellation of the Southern Fish. He was the first exoplanet that could be directly, that is optically visible light detected. However, a planetary system in the infrared light was almost simultaneously discovered by HR 8799.


The main sequence star Fomalhaut of spectral type A was, since the IRAS satellite around him a vast dust ring (similar to the Kuiper Belt ) was discovered in the 1980s, a goal of finding planetary systems. 2004 was determined by observations of the Hubble Space Telescope that this dust disk has a sharp inner boundary. The researchers assumed that a massive planet would affect the dust disk gravitationally. Another clue was the fact that the dust disk to the star is elliptical and not exactly centered.

Since 2001, Fomalhaut was observed by a working group led by Paul Kalas of the University of California, Berkeley. Repeated Hubble recordings between 2004 and 2006 showed a point of light within the dust ring, which moves obviously on a Keplerian orbit around Fomalhaut. The discovery was published in November 2008. This was until then the first direct visual evidence for the existence of exoplanets.

2010, the system was again photographed by the Hubble telescope. On the new photo Fomalhaut b differs from its previously calculated path. This prompted skeptics to question the existence of Fomalhaut b in question. However, the differences could be explained by the use of another camera.

Web properties

Least of uncertainty regarding the web properties of Fomalhaut b. It orbits the central star at an average distance of about 115 astronomical units (AU ) or 17.2 billion kilometers. That's about 18 AE within the inner boundary of the dust disk. Due to the eccentricity of the orbit of 0.11 varies the distance 102-128 AE and currently stands at about 119 AU. Fomalhaut b is therefore almost four times as far from its central star as Neptune, the outermost gas planet in the solar system. From the orbit results in an orbital period of about 872 years.

Physical Properties

The physical properties of Fomalhaut b may be extrapolated only from the orbital parameters. The calculations assume that Fomalhaut b maximum can be as massive as Jupiter is about three times, otherwise it would destroy the dust disk. The probable mass is between half and twice the mass of Jupiter. Its radius would correspond in each case approximately to that of Jupiter.

The surface temperature is expected to remain the (-200 ° C) correspond to the Neptune as the higher luminosity Fomalhauts compensates for the distance. The planet appears a billion times fainter than Fomalhaut. This is still much brighter than the planet's surface would leave you alone expect. One possible explanation is that Fomalhaut b is surrounded by a massive ring system of ice and dust, which should correspond to the dimensions of the orbits of the Galilean moons around Jupiter.