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Last Updated: Wednesday, 6 September 2006, 10:10 GMT 11:10 UK
A view from the cosmic shoulder
By Dr Chris Riley
Presenter, The Cosmic Hunters, BBC Radio 4

Artist's impression of the icy "super-Earth" (Image: ESO)
New detection techniques help astronomers search for new planets
Astronomers have discovered over 200 new worlds orbiting our closest 5,000 stars; all this despite modern telescopes lacking the power to see planets beyond our Solar System.

Others are searching for light from the first stars to shine in the Universe over 13 billion years ago, a task which has so far proved impossible.

Around the world these scientists are doing what they do best - detecting the things they cannot see amid a background of things they can.

In the late 1980s and early 1990s, a maverick band of astronomers in Europe and the US decided that simply being unable to see a planet orbiting another star was insufficient reason for not looking.

Their success hinged on an attempt to pick up the subtle motions of stars they could see being tugged by orbiting planets which they couldn't.

This was a daunting prospect, given how subtle such motions might be. "A big planet only pulls its star at the speed that a human can run," explains Professor Geoff Marcy from the University of California at Berkeley, one of the original planet-hunting pioneers.

Attempts to detect such tiny motions across light-years of space took almost 10 years, recalls Marcy. "And the first planets found to be causing them were real giants - many times the size of Jupiter and orbiting so close to their stars they caused relatively large, more easily detectable stellar wobbles."

To look back across 13 billion years of time to when the Universe was just a baby is a remarkable accomplishment for human kind
Garth Illingworth
Today, the prizes in this field are to be found in locating smaller planets.

Worlds of the sizes currently being sought will only wobble their stars at the speeds an insect crawls across a table - just a few centimetres per second. But such trivial motions, barely detectable by current technology, could betray the presence of something of immense significance: another Earth-sized planet.

This is the grail which keeps the teams working on this quest whilst still potentially decades away from the first actual image of such a world.

Early dawn

Also working beyond the limits of their telescopes, in another field of astronomy, are the scientists looking for light from the very first stars to shine in the cosmos.

Such ancient light from the first few hundred million years after the Big Bang has been dimmed and reddened by over 13 billion light-years of space travel across the expanding Universe.

"It is tens of billions of times fainter than the stars we see in our night skies," says Professor Garth Illingworth from the University of California, at Santa Cruz, whose team used the combined power of the Hubble and Spitzer Space Telescopes to find galaxies of stars which developed around 400-600 million years after the Big Bang.

Hubble Space Telescope.  Image: Nasa
The Hubble Space Telescope is key to early galaxy detection
Detection of the cosmic dawn, a few hundred million years before this, might have to wait for the launch of the successor to Hubble, the James Webb Space Telescope, planned for 2013.

But Professor Richard Ellis at the California Institute of Technology has already snatched some time on a natural "telescope of the future", as he calls it.

By using the gravitational lensing effect of clusters of nearer galaxies, he has been able to boost the effective magnification of the already mighty Keck telescope by as much as 50 times.

His efforts have so far revealed galaxies that existed just 300-400 million years after the Big Bang.

Even this does not take us back to the first stars, which would have materialised perhaps just 100 million years into the Universe's life and lived, on cosmic timescales, fleeting lives.

But such ingenuity might yet reveal them, years before the James Webb telescope gets to join the search.

The audacity needed to strive for the precision required to find planets of Earth mass around other stars, or to embark on the hunt for the first stars to shine in the Universe, is easy to overlook.

But the triumph, against the odds, of actually achieving these Herculean goals is also often hidden behind the headlines.

As Garth Illingworth points out: "To look back across 13 billion years of time to when the Universe was just a baby is a remarkable accomplishment for humankind."

The Cosmic Hunters series begins on Wednesday, 6 September, 2006 at 2100 BST on BBC Radio 4. You can also listen online for 7 days after each broadcast at Radio 4's Listen again page.

Hubble glimpses faintest stars
17 Aug 06 |  Science/Nature
Sunshade to look for distant life
05 Jul 06 |  Science/Nature
Planet shine 'to aid life search'
24 May 06 |  Science/Nature
Planet hunters find 'super-Earth'
14 Mar 06 |  Science/Nature
Smallest Earth-like planet found
25 Jan 06 |  Science/Nature
Glow from first stars revealed
03 Nov 05 |  Science/Nature
Smallest extrasolar planet found
13 Jun 05 |  Science/Nature
Smallest extra-solar planet found
14 Feb 05 |  Science/Nature


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