Page last updated at 17:31 GMT, Friday, 3 July 2009 18:31 UK

Planck achieves ultra-cold state

Planck (Esa)
Planck is now the "coolest thing in space"
Planck will survey the famous Cosmic Microwave Background
This ancient light's origins date to 380,000 years after the Big Bang
It informs scientists about the age, shape and evolution of the cosmos
Planck's measurements will be finer than any previous satellite

Europe's Planck observatory has reached its operating temperature, making it the coldest object in space.

The observatory's detectors have been chilled to a staggering minus 273.05C - just a tenth of a degree above what scientists term "absolute zero."

Launched in May, Planck will survey the "oldest light" in the Universe.

Its detectors, or bolometers, should see detail in this radiation that offers new insights into the age, contents and evolution of the cosmos.

Although laboratory set-ups have got closer to absolute zero than Planck, researchers say it is unlikely there is anywhere in space currently that is colder than their astronomical satellite.

This frigidity should ensure the bolometers will be at their most sensitive as they scan the sky for the target light.

The remarkable conditions are maintained, in part, by always pointing Planck away from the heat of the Sun. Shields and baffling get the telescope down to about -220C.

Three active refrigeration systems then lower the onboard environment at the heart of the observatory extremely close to the state of zero heat energy - when, theoretically, atoms would stop moving.

Planck has been sent to an observation position some 1.5 million km from Earth. Its first data release is expected next year.

The European Space Agency mission was launched along with another telescope called Herschel. This second observatory is sensitive to shorter wavelength radiation than Planck and will be studying the birth of stars and the evolution of galaxies.

It, too, carries bolometer technology, but operates at a slightly warmer temperature - just 0.3 of a degree above absolute zero.

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