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		<field id="8018" index="0" type="number">23032</field>

		<subject index="0" >Re: SECOND IMAGE - M51 WHIRLPOOL GALAXY</subject>

		<tonames index="0" >S194 06E real time observing</tonames>

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Here are two images of M51  the whirlpool galaxy

they are through different filters...

The B-bandfilter only lets through blue light, whilst the R band filter only lets
through red light.

Notice that the spiral arms of the galaxy are more prominent in 'B'

This is because the arms are where new, young stars are formed.  And the brightest
young stars are the hottest, massive stars. These are blue in colour (because they're
very hot - 10,000 degrees to 50,000 degrees surface temperature) , and so they
dominate what we see.

The core of the galaxy is redder, this contains older, cooler, lower mass stars - all
the hot blue stars there have burnt out long ago.

Andy