Dear Science and Astronomy friends,
Star 'gnome' is nuclear surprise
http://news.bbc.co.uk/1/hi/sci/tech/4319061.stm

Star 'gnome' is nuclear surprise

A comparison between our Sun, Jupiter and the stellar "gnome"
A shining star has been located that is not much bigger than Jupiter, the
biggest planet in our Solar System.
The discovery is fascinating, say scientists, because it shows how small
an object can be and still trigger the nuclear reactions for sunshine.

The existence of the star, known as OGLE-TR-122B, was confirmed by the
Very Large Telescope (VLT) in Chile.

Sited in the Carina constellation, the stellar "gnome" was seen to pass in
front of a much bigger companion star.

As it did so, it dimmed the companion's light received at the VLT, a
facility run by the European Southern Observatory organisation (ESO).

In a volume

It is not known precisely how big an object needs to be to shine. At some
point a gas body will become so massive that the gravitational forces pulling
material into its core will initiate fusion reactions - just like those at the
core of our Sun that give us light.

What is interesting is that although OGLE-TR-122B is a mere 16% larger
than Jupiter, it is actually 96 times more massive.

"Imagine that you add 95 times its own mass to Jupiter and nevertheless
end up with a star that is only slightly larger," suggests Claudio Melo, from
ESO and member of the team of astronomers who made the study.

"The object just shrinks to make room for the additional matter, becoming
more and more dense."

Indeed, the density of OGLE-TR-122B is more than 50 times greater than
that of our own Sun.

Setting limits

The stellar gnome shines, but not very brightly - especially when compared
with the energy released by its large companion star.

"This result shows the existence of stars that look strikingly like
planets, even from close by," said Frederic Pont, of the Geneva Observatory,
Switzerland.

"Isn't it strange to imagine that even if we were to receive images from a
future space probe approaching such an object at close range, it wouldn't be
easy to discern whether it is a star or a planet?"

What is remarkable, however, is that OGLE-TR-122B is actually smaller than
some of the planets discovered recently outside our Solar System.

Details of the study on OGLE-TR-122B will appear in a forthcoming edition
of the journal Astronomy & Astrophysics.




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