Wednesday, 16 January 2013

When space isn't cold enough

Not a Blue Peter model - the actual Herschel Space Observatory
We are used to thinking of space as a cold place. And it is, sort of - but not always in the ways you might expect.

For instance, if you were suddenly dropped into space you might assume that the minimal temperature out there would mean that your blood would freeze solid in your veins, while simultaneously trying to boil where any is exposed due to a lack of pressure. But here's the thing. It won't boil - your circulatory system will keep it under pressure - and it won't freeze because a vacuum makes a great insulator. Remember vacuum flasks - there's a lesson there. The only heat you will lose is through radiation and you aren't hot enough to do that quickly.

Even so, it's rather ironic that space just isn't cold enough for the Herschel Space Observatory. It was sent up with 2160 litres of liquid helium to keep it cool. but that is due to run out by the end of March, leaving the Herschel to die of warmth in space - without that helium, the electromagnetic radiation emitted by the satellite itself will be enough to mask the subtle stream of photons it has been detecting.

The Herschel has done great work on helping us understand how stars and galaxies are formed, peering back around 10 billion years in time, picking up weak sub-millimetre light from the dust around newly formed stars. The good news, though, is that although the Herschel is soon to stop functioning, according to Steve Eales at the University of Cardiff, an astronomer who leads one of the telescope’s largest surveys,  'the treasure trove of Herschel data will be picked through by astronomers for years to come.' That's good to know.

Thanks to Physics World (also featuring an excellent article by me (ahem) on the need for double blind experiments in physics to deal with experimenter bias in the January edition) for this info.

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