Spying on the stars

Astronomers in Hawaii have captured the first ever direct pictures of a group of three planets orbiting around a star - obviously not including our own solar system.  Publishing their results in the journal Science this week, the researchers believe that it could be the first step on the road to discovering another earth.

Led by Christian Marois from Canada, and including scientists from the US and the UK, the team first used the Gemini North and Keck II telescopes to spot two new planets orbiting around the star HR7899 back in October last year. Then this summer they found a third planet even closer to the star.

This is the first time we have directly imaged a family of planets around a normal star outside of our solar system. One of the team said, "Until now, when astronomers discover new planets around a star, all we see are wiggly lines on a graph of the star's velocity or brightness. Now we have an actual picture showing the planets themselves, and that makes things very interesting."

The star at the centre of this new system, HR 8799, is about 130 light years away from us here on Earth, is about one and a half times the mass of the sun, and 5 times as bright. It's also younger, with a big far-out dust disk, similar to our own Kuiper belt.  

The planets, which formed about sixty million years ago, are young enough that they are still glowing from heat released as they contracted.  And they're about seven an ten times the mass of Jupiter, suggesting that the system may be a scaled-up version of our own Solar System, but going round a brighter and bigger star.

For space physicists, HR 8799 is a great discovery, allowing them to test predictions for planet formation, evolution, and atmospheric physics. And they could be prime targets for space exploration in the future.