EUROPE is to launch the most powerful space telescope ever built with the ability to capture light from stars that were born and died up to 13 billion years ago.
The Herschel space telescope, named after an 18th-century British astronomer, could help solve the mystery of how galaxies and stars formed and how these processes eventually gave rise to life-bearing planets like Earth.
Last week, the assembly of Herschel moved into its final stage at the European Space Agency's (ESA) research and technology centre in Noordwijk, Holland, with the arrival of the 3.5 metre diameter mirror that will become the heart of the instrument after its launch this summer.
"We will be able to look at some of the oldest objects in the universe," said Bruce Swinyard, professor of astronomical instrumentation at Cardiff University, who has helped design the telescope. "It is going to tell us a great deal about how galaxies originally formed."
Herschel, part-funded with £17m from Britain's Science and Technology Facilities Council, will be far more powerful than Nasa's Hubble space telescope, which has a mirror of just 2.4 metre diameter.
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It will, however, complement rather than supplant Hubble because it operates in the infrared spectrum, detecting radiation invisible to the human eye. Hubble, by contrast, collects mainly visible light.
One of the mysteries that Herschel is designed to solve is the growth of galaxies. The universe is dominated by such galaxies, each typically containing several hundred billion stars and surrounded by huge areas of emptiness. The Milky Way, which includes Earth, is one of them.
The universe is thought to have emerged in the "big bang" about 14 billion years ago. However, once the initial burst had died away, the universe went dark for hundreds of millions of years. During that time, known as the cosmological dark ages, the processes that gave rise to galaxies and stars must have begun, but nobody knows how.
Astronomers cannot even tell if stars arose first and then drew together to form galaxies or if it was the other way round, with huge clouds of gas accumulating and then condensing into stars.
Part of the problem is that since the big bang the universe has expanded at an ever-increasing rate. This has "stretched" the radiation emitted far back in time so that it has become infrared and invisible.
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"The light from those times is now all deep within the infrared spectrum where we cannot yet see it," said Swinyard. "The instruments on Herschel will be the first to pick it up and tell us something about what happened back then."
Herschel will carry three main scientific instruments, including the spectral and photometric imaging receiver built by Cardiff University.
The kind of secrets that might be unveiled by Herschel were hinted at by an earlier ESA probe, the infrared space observatory (ISO), when it peered, for example at the Andromeda galaxy, one of the closest to our own. ISO showed it was made of concentric rings. These were so cold at -260C that they showed up only in infrared.
Herschel, which will be launched on one of ESA's Ariane rockets, will be accompanied into space by the Planck probe, another European project.
David Southwood, ESA's director of science, said: "These two missions are among the most important we have ever launched."
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Herschel, discoverer of Uranus
Sir William Herschel was born in Germany in 1738, but moved to Britain after serving here as a soldier. He became the King's astronomer in 1782 a year after discovering the planet Uranus.
He came across infrared radiation by accident when splitting sunlight into its constituent colours by passing it through a prism. Herschel deduced there must be radiation when a thermometer showed a higher temperature just beyond the red end of the spectrum.