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		<subject index="0" >Re(2): SECOND IMAGE - M51 WHIRLPOOL GALAXY</subject>

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

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Thanks, Andy - great images.  Are you doing the pimage processing or is that being done by John and Lindsey in the dome?

Andy Norton on 15 May 2006 at 22:28 +0000 wrote:
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