Fomalhaut b

Fomalhaut b

At this point everybody knows about Fomalhaut b, the first extrasolar planet photographed via visible-light.

(If you haven’t: Hubble Telescope has taken the first visible-light snapshot of the planet, named Fomalhaut b, a tiny point orbiting the bright southern star Fomalhaut, 25 light-years away in the constellation Piscis Australis. An immense debris disk surrounds the star. In this debris disk, estimated to be no more than three times Jupiter’s mass, lies Fomalhaut b.

Fomalhaut has been a candidate for planet hunting ever since an excess of dust was discovered around the star in the early 1980s infrared. In 2004, a coronagraph camera produced the first-ever resolved visible-light image of a large dust belt surrounding Fomalhaut, similar to the Kuiper Belt. In 2005 it was proposed that the ring was being gravitationally modified by a planet lying between the star and the ring’s inner edge. Later there was confirmation that the ring is offset from the center of the star. The sharp inner edge of the ring is also consistent with the presence of a planet that gravitationally “shepherds” ring particles.

A follow-up image in 2006 showed that one of the objects is moving through space with Fomalhaut but changed position relative to the ring since the 2004 exposure. The amount of displacement between the two exposures corresponds to an 872-year-long orbit as calculated from Kepler’s laws of planetary motion.

Now, Hubble has actually photographed a point source of light lying 1.8 billion miles inside the ring’s inner edge. The results are being reported in the November 13 issue of Science magazine.)

The idea of “other planets” isn’t new. Newton already mentioned the possibility that fixed stars are the “centers of other like systems”. In the 19th century, detected orbital anomalies were explained by claims of planetary systems, not very different from the preferred method nowadays.

But how many extrasolar planets do we know of? 326, according to the ExtraSolar Planet Encyclopedia. You can get the entire list here.