Friday, 19 February 2010

Photographing our neighbor

Whenever I think of a classic spiral galaxy I think of something like this:

The Andromeda galaxy - M31

Andromeda, this swirling mass of stars, is a naked eye object - well, it is on clear, dark nights away from the glow of all or any street lights. It's the closest large galaxy to our own Milky Way, a mere 2½ million light years away, and is our sibling if not quite our twin. Together we are locked in an eternal dance of gravitation and it's thought that, at some time in the far distant future, we will pass through each other and perhaps even merge.

It is a beautiful thing, but looking with our own eyes can only reveal part of that beauty. Last December saw the launch of WISE (Widefield Infrared Survey Explorer), a space telescope designed to take images at wavelengths between 5 and 35 times longer than the human eye can see. It is discriminating between different sources of heat. The first results have just been released and are very impressive as this glorious new image shows.

Yes, that's Andromeda again. A little rotated compared to the top image but you get that in astronomy.

The bright yellows and reds are bands of dust, heated up by young stars forming within the clouds. The blue haze comes from older stars which have long absorbed or blown away any gas and dust. You can see the same dust in the optical picture as dark lanes blotting out the starlight. Now it comes into proper focus, beautiful.

Images from Big Cigar Astronomy and APOD.

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