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View Full Version : Crab Nebula noticeably expanding



ToSeek
2001-Dec-27, 02:39 PM
...in photos taken thirty years apart:

http://antwrp.gsfc.nasa.gov/apod/ap011227.html

Hale_Bopp
2001-Dec-27, 03:05 PM
Using round numbers of 30 years expanding at 1100km/s, it has expanded by ~1*10^12km!

Just thought it would be fun to run the numbers /phpBB/images/smiles/icon_smile.gif

Rob

GrapesOfWrath
2001-Dec-27, 04:18 PM
And, since 1000km/s is about 1/300 the speed of light, in thirty years it should have expanded 1/10 of a light year. Since the Nebula is ten light years across, it has increased 1 per cent in thirty years. I would have guessed a little more.

It originated in 1054, about a thousand years ago. So, it has averaged, over that time, about one light year a century, 1/3 of a light year in thirty years. So, it is slowing down nicely.

Hale_Bopp
2001-Dec-27, 04:28 PM
Right on target...a light year is about 9.47*10^12km, so we are looking at pretty close to 1/10th of a light year.

Boy, don't you love it when the numbers work out /phpBB/images/smiles/icon_smile.gif

Rob

Azpod
2001-Dec-27, 06:11 PM
On 2001-12-27 09:39, ToSeek wrote:
...in photos taken thirty years apart:

http://antwrp.gsfc.nasa.gov/apod/ap011227.html



Incredible... I was especially impressed that the second image was made from a telescope in the visitor's center for the telescope that snapped the original pic!

Hale_Bopp
2001-Dec-27, 07:23 PM
Note that the original was taken on a photographic plate and the second on a CCD camera. Modern CCD cameras can capture relatively faint objects much quicker than a photographic plate!

Not only that, image processing allows you to subtract sky background, make a flat field correction, and all kinds of other neat image processing tricks. Amateurs with modest telescopes can take some stunning astrophotos these days! Lots of amateurs own .4 meter telescopes, which is what took the second photo!

I read the blurb about the original photo. Interesting that it was actually taken on color film! That is kind of unusual for a professional observaotry, but I guess you can get away with it using a 4.0 meter telescope on a relatively bright object!

Rob