Capture the cosmos > Solar system > Tales of: Image of a planet orbiting another star

Like the hundreds of other known extrasolar planets, Fomalhaut b is a gas-giant world, estimated to be no more than three times Jupiter’s mass. Astronomers, however, suspect it might have one striking characteristic that separates the newly discovered planet from its extrasolar brethren. It may be surrounded by an immense Saturn-like ring system.  “The planet is brighter than expected for an object of three Jupiter masses,” says Paul Kalas of the University of California, Berkeley, and the study’s lead researcher. “If we’re seeing light in reflection, then it must be because Fomalhaut b is surrounded by a planetary ring system so vast, it would make Saturn's rings look pocket-sized by comparison. The ice and dust reflect starlight.” Perhaps Fomalhaut b’s ring will eventually coalesce to form moons.”

An immense debris disk about 21.5 billion miles across surrounds the star. Astronomers have long considered the Fomalhaut system as a potential breeding ground for planets because of the star’s vast debris ring. “Fomalhaut b may actually show us what Jupiter and Saturn resembled when the solar system was about 100 million years old,” Kalas says. Circumstantial evidence for Kalas’ planet theory came from Hubble’s confirmation that the Fomalhaut ring is offset from the star’s center. The disk’s sharp inner edge is also consistent with the presence of a planet that gravitationally “shepherds” particles within it.  

Kalas and his team plan follow-up Hubble observations in 2009 to further study the Fomalhaut system. "We hope those observations will greatly refine what we know about Fomalhaut b’s orbit,” Kalas says. “New measurements of the brightness at various wavelengths also will help in deciphering the physics that makes Fomalhaut b shine.” Perhaps future observations will turn up more planets. Fomalhaut b may be the outermost planet in a whole solar system of planets, just as Neptune is in our solar system.

Astronomers, however, may have to wait for the James Webb Space Telescope, slated to launch in 2014, to find out whether planets in the Fomalhaut system could sustain life.

“We'll probably have to wait for the James Webb Space Telescope to give us a clear view of the region closer to the star where a planet could host liquid water on its surface,” Kalas says.

Capture the cosmos > Solar system > Tales of: Image of a planet orbiting another star