Balloon telescope's star vision

The "baby-boomer Universe" has been seen in unprecedented detail by a telescope slung beneath a balloon.

The BLAST experiment only flew twice and was destroyed on its final mission, but its observations and technology have had a major impact on astronomy.

The telescope probed an epoch in cosmic history some 7-10bn years ago when star formation was prolific.

Scientists tell Nature magazine that BLAST's data will help them understand better how the Universe has changed.

"In the distant Universe, galaxies look very different. They're much more massive, forming stars at a very high rate of thousands per year. If you look at our own Milky Way Galaxy today, it forms perhaps just four stars a year," explained Dr Enzo Pascale who led the Cardiff University, UK, team working on the project.

Astronomers established in the 1980s and 1990s that the cosmos was extremely bright at far infrared and sub-millimetre wavelengths - at least as bright as it appears at the optical wavelengths we can detect with our eyes or with a telescope such as Hubble.

Scientists suspected this light, which covered the entire sky, was coming from distant, very luminous galaxies where countless new suns were bursting into life from within huge clouds of very dusty gas.

But it was a difficult question to address because our own atmosphere actually absorbs this type of radiation and makes ground observations extremely tricky.

With the high-flying Balloon-borne Large-Aperture Sub-millimeter Telescope (BLAST), scientists had the means to get above this problem and try to detect the individual source galaxies.

In its Nature paper, the BLAST project team reports that the telescope identified hundreds more target galaxies than had previously been seen and could describe them in finer detail than ever before.

The team says the peak of the Far Infrared Background radiation, as it has become known, is indeed related to distant "starbust" galaxies - objects that are being seen when the Universe was about a third of its present age.

"It pins completely the origin of the infrared background on star and galaxy formation," said Dr Pascale.

Looking at the sedate cosmic neighbourhood we inhabit today, it is hard to appreciate just how different conditions were in the young, bustling Universe.

"These early galaxies would have crashed together, and this crashing would have stimulated a huge amount of star formation in that new galaxy that's being created," explained Dr Mark Devlin, BLAST group leader from the University of Pennsylvania, US.

"That's where these ultra-luminous galaxies came from; it's quite spectacular."

BLAST was destroyed in the Antarctic when it was dragged for 200km along the ice by a parachute that failed to detach properly on landing.

The story, though, does not end there. The sub-millimetre camera on BLAST was a forerunner for the one being launched on 6 May on the European Space Agency's flagship Herschel observatory.

The billion-euro space telescope will travel some 1.5 million km from Earth to enjoy the very best observing conditions. The astronomical satellite is expected to identify many thousands of starburst galaxies.

"We've shown what's out there and what you should be looking for. Herschel will really go and nail it," said Dr Devlin.

"It will be a much more stable instrument, observing over a much longer period of time, over larger areas; and will go deeper."

In addition to the universities of Cardiff and Pennsylvania, the BLAST project called on the expertise in the universities of Brown, Toronto, Puerto Rico, Miami, and British Columbia; and the Jet Propulsion Laboratory in California, and the Laboratoire APC in Paris.

Jonathan.Amos-INTERNET@bbc.co.uk

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