First pics of new worlds

14 November 2008

In a world first, scientists have snapped pictures of planets in other solar systems. Even though they orbit stars trillions of kilometres away, the
hi-tech cameras used to capture the images could find many more planets and help us understand how Earth formed.

This research was published in the journal Science on 14 November 2008.

Our own Solar System is one of many within the Milky Way Galaxy.

Image: 2MAS/UMass?IPAC-Caltech/NAS/NSF

In breakthrough reports, two groups of scientists have described how they have captured images of previously unknown planets. This is difficult because even huge planets can be lost in the bright glare of the star they orbit.

Astronomers have indirectly found over 200 planets by spotting whether stars 'wobble' as planets spin past. But these new findings show it's possible to pick out a planet from bright starlight. This means we can now find out a planet's size, temperature, gravity and the make-up of its atmosphere.

The star HR 8799 in the constellation of Pegasus, around which three planets have just been pictured.

Image: National Research Council Canada

One team used infrared cameras in ground-based telescopes. These cameras sense heat from the planets by artificially wiping out the intense energy from their star. After picking the best places to go planet-hunting, they found and photographed three massive planets circling a star 128 light years away.

'This is the first image ever taken of a multi-planet solar system. It's also the first image of planets that we believe formed in the same conditions as the planets of our own Solar System.'
Christian Marois, project leader, Herzberg Institute of Astrophysics

Around the huge star, the three planets can be spotted.

Image: National Research Council Canada

At the same time, another scientific team have been looking for planets orbiting nearby stars using a completely different approach.

Project leader Paul Kalas explains: 'We used a specialised camera on the Hubble Space Telescope which blocks the light from stars so that astronomers can study faint objects nearby.'

Paul Kalas, astronomer, University of California.

Using Hubble, Paul and the team captured images of a planet in the dust cloud of a star called Fomalhaut, 25 light years from Earth. They took images two years apart to prove that the object was orbiting the star, which makes it a planet, not another background object.

The planet Fomalhaut b can be seen in its orbit in 2004 and 2006.

Image: Paul Kalas, University of California, Berkeley

Astronomy expert Mark Wyatt says these findings are great news for science: 'Not only does this discovery show that we have the capability to discover these planets, but to capture images of them!

'Undoubtedly this is an important step towards understanding how our Solar System developed, and how other planetary systems form.'

Mark Wyatt, astronomer, University of Cambridge.

Image: Jason Cowan, UK ATC, ROE, Edinburgh

Might these planets hold life?

'These are all hot gas giants bigger than Jupiter, so aren't very habitable. But they could have moons with liquid water. Also, this solar system could be very similar to ours, with other rocky planets orbiting nearer to the star,' says Christian.

Christian Marois, project leader, Herzberg Institute of Astrophysics.

'But the solar system we saw is only 60 million years old and it's believed that it took 600 million years for life to develop here. So even if there is an Earth-like planet, it's still probably too inhospitable to support life. But maybe in 550 million years...!'
Christian Marois

The Gemini Planet Imager, built into the Gemini telescope in Chile, South America, will start looking for planets in 2011.

Image: Gemini Observatory/AURA

The teams' next steps are to work out more about the make-up and physical characteristics of the planets. Soon, they hope to be able to use newly designed cameras that can take images of smaller, fainter planets which could be more like Earth.

Further in the future, NASA's Terrestrial Planet Finder spacecraft will go seeking out smaller, rocky planets to look for signatures of life from a distance. Might one of these newly glimpsed solar systems hold planets supporting life forms? We'll have to wait to find out...

The two Terrestrial Planet Finder spacecraft will spot planets using infrared- and starlight-blocking cameras like those used by the scientists in this article.

Image: NASA