Advanced Imaging


Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

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Dusty debris disk
Dusty debris disk.
Jack St. Clair Kilby
Jack St. Clair Kilby, inventor of the monolithic integrated circuit.

Did Hubble Find a Tenth Planet?

The headline may sound like the stuff of supermarket tabloids, but there appears to be a planet circling a nearby star.

According to NASA, its Hubble Space Telescope has returned images showing a dusty ring around Formalhaut (HD 216956), a bright star that is 25 light years away. Formalhaut has been around for the last 200 million years; it is younger than the sun, which is 4 billion years old. The star was initially found by astronomers in 1984, when infrared astronomers first detected heat from a dusty debris disk around the star, but they could only speculate about any planets that may have condensed out of the dust.

The debris formed the same time Formalhaut formed. At that time, planets and moons were bombarded by asteroids and comets; as a matter of fact, the craters on the moon were formed by those same bombardments. When the planets had formed, its debris still floated around in its orbit.

Astronomers used the Advanced Camera for Surveys' (ACS) coronagraph aboard Hubble to block out the light from the star so they could see the ring. They also noticed that the center of the ring is 15 astronomical units (AU) or 1.4 billion miles away from the star. This is a distance equal to nearly halfway across our solar system.

The observed offset of the belt implies a planet in a highly eccentric orbit that sweeps up the dust in the disk, in the same way Neptune and the larger planets of our solar system have vacuumed out a hole in the debris disk around the sun, leaving a distant ring of rocky debris called the Kuiper Belt.

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