Comments on: The Ghost of Mirach http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Mon, 23 Nov 2009 07:20:25 -0600 http://wordpress.org/?v=2.8.4 hourly 1 By: marko http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144652 marko Thu, 01 Jan 2009 18:30:48 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144652 I have one of those old-fashioned bitmap editors where you can combine clippins with "xor", "not or" operations. I've done this with these two images, and most stars in it really correspond on a per-pixel basis. Amazing, how the visible and UV version differ and at the same time resemble each other. I have one of those old-fashioned bitmap editors where you can combine clippins with “xor”, “not or” operations. I’ve done this with these two images, and most stars in it really correspond on a per-pixel basis. Amazing, how the visible and UV version differ and at the same time resemble each other.

]]> By: IVAN3MAN http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144433 IVAN3MAN Wed, 31 Dec 2008 19:28:25 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144433 @ Gary Ansorge, This is an extract from Wikipedia: <b><u>Gravitational Redshift vs. Gravitational Time Dilation</u></b> <blockquote>When using special relativity's relativistic Doppler relationships to calculate the change in energy and frequency (assuming no complicating route-dependent effects such as those caused by the frame-dragging of rotating black holes), then the Gravitational redshift and blue-shift frequency ratios are the inverse of each other, suggesting that the 'seen' frequency-change corresponds to the actual difference in underlying clock-rate. Route-dependence due to frame-dragging may come into play, which would invalidate this idea and complicate the process of determining globally-agreed differences in underlying clock rate. While gravitational redshift refers to what is seen, gravitational time dilation refers to what is deduced to be 'really' happening once observational effects are taken into account.</blockquote> (Click on my name for the link to the full article.) @ Gary Ansorge,

This is an extract from Wikipedia:

Gravitational Redshift vs. Gravitational Time Dilation

When using special relativity’s relativistic Doppler relationships to calculate the change in energy and frequency (assuming no complicating route-dependent effects such as those caused by the frame-dragging of rotating black holes), then the Gravitational redshift and blue-shift frequency ratios are the inverse of each other, suggesting that the ’seen’ frequency-change corresponds to the actual difference in underlying clock-rate. Route-dependence due to frame-dragging may come into play, which would invalidate this idea and complicate the process of determining globally-agreed differences in underlying clock rate.

While gravitational redshift refers to what is seen, gravitational time dilation refers to what is deduced to be ‘really’ happening once observational effects are taken into account.

(Click on my name for the link to the full article.)

]]> By: Gary Ansorge http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144380 Gary Ansorge Wed, 31 Dec 2008 15:51:59 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144380 I have a slight confusion. How do we tell the difference between a red shift due to velocity, as in for distant quasars and a red shift due to a strong Gravity field? From what I can recall of relativity theory, there should be no difference,,, GAry 7 I have a slight confusion. How do we tell the difference between a red shift due to velocity, as in for distant quasars and a red shift due to a strong Gravity field? From what I can recall of relativity theory, there should be no difference,,,

GAry 7

]]> By: Ted http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144298 Ted Wed, 31 Dec 2008 04:44:26 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144298 If only I had read this before LAST night. Was out in the back yard with binoculars hunting for M31 and Mirach happened to be at the exact zenith while I was observing. It made a nice starting point for hopping over to see the "cool" stuff. Looks like NGC 404 is 11th magnitude though, so no casual observing for me. Still pretty cool to know it's there! If only I had read this before LAST night. Was out in the back yard with binoculars hunting for M31 and Mirach happened to be at the exact zenith while I was observing. It made a nice starting point for hopping over to see the “cool” stuff.

Looks like NGC 404 is 11th magnitude though, so no casual observing for me. Still pretty cool to know it’s there!

]]> By: Dean W. Armstrong http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144260 Dean W. Armstrong Wed, 31 Dec 2008 01:55:34 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144260 Nice writeup Phil. I happened upon this galaxy while recalibrating my pointing system in late November, and as usual have to rush to finish processing. <a HREF="http://dwarmstr.blogspot.com/2008/12/mirachs-ghost.html" rel="nofollow">Here's my take on Mirach's Ghost</A> Nice writeup Phil. I happened upon this galaxy while recalibrating my pointing system in late November, and as usual have to rush to finish processing.

Here’s my take on Mirach’s Ghost

]]> By: andy http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144241 andy Wed, 31 Dec 2008 00:39:39 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144241 I wonder what the sky would look like from a planet in a typical gas poor lenticular galaxy - something like the "Milky Way" but without the dark clouds obscuring most of the stars, perhaps? Could be quite impressive... I wonder what the sky would look like from a planet in a typical gas poor lenticular galaxy – something like the “Milky Way” but without the dark clouds obscuring most of the stars, perhaps? Could be quite impressive…

]]> By: Jadehawk http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144235 Jadehawk Wed, 31 Dec 2008 00:22:49 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144235 the universe is violent and pretty. I like the name "Ghost of Mirach", it does poetic justice (no, not THAT kind of poetic justice) to the beauty and mystery of space. the universe is violent and pretty. I like the name “Ghost of Mirach”, it does poetic justice (no, not THAT kind of poetic justice) to the beauty and mystery of space.

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