Source: BBC News
http://news.bbc.co.uk/1/hi/sci/tech/3707185.stm



Hubble sees 'planet' around star

The historic first image of a planet circling another star may have
been taken by the Hubble Space Telescope.

The "planet", 5-10 times the mass of Jupiter, is orbiting a small white
dwarf star about 100 light-years away.

Astronomers are being cautious, saying they require more data to be
sure it really is a planet and not a background object caught in the
same field of view.

Confirmation will come if follow-up observations can show the planet
and the star moving together through space.

Over the past 10 years, scientists have discovered more than 120
so-called exoplanets. However, all have been found by indirect methods
- none was photographed directly.

Glowing ball

The new Hubble image was taken by John Debes, a graduate student at
Pennsylvania State University, US, as part of a project to look for
planets around other stars.

"The big problem in seeing such planets is not one of sensitivity but
of contrast," he told BBC News Online. "The presence of a bright parent
star makes the relatively dim planet difficult to see."

That is why Debes and his colleagues looked for planets around dim
white dwarf stars - stars at the end of their lifetimes that have
shrunk to a glowing ball the size of the Earth.

"We surveyed seven white dwarfs and around three of them we saw what
might be a planet.

"In one of them, the planet could be only a few times the mass of
Jupiter," he said.

The unnamed world is about the same distance from its star as Neptune
is from our Sun.

Awaiting confirmation

The planet would have begun its life several billion years ago much
closer to its parent star.

This star would have been more massive and brighter than our Sun. At
the end of its life, it would have expanded and destroyed any nearby
planets.

Only the more distant planets would have survived and, as the star lost
mass, their orbits would have expanded due to the star's reduced
gravity.

Debes remains cautious about the object until it has been shown to be
definitely associated with the white dwarf.

"If it is a planet and not a background object that happens to be in
the same direction, we should see it move across the sky with the star
in a few months," he said.

Debes plans follow-up observations with the Hubble Space Telescope or
possibly with ground-based telescopes.