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. Tue, 14 Feb 2012 15:46:45 +0000 hourly 1 http://wordpress.org/?v=3.2.1 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.

]]> By: John Paradox http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144207 John Paradox Tue, 30 Dec 2008 22:30:39 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144207 <I>KC Says: I’ve heard NGC 404 referred to as the Phantom Galaxy</I> So would that be the galaxy in George Lucas' STAR WARS series? It is far, far away (at least *I* consider 11 million LY far, far away). J/P=? KC Says:
I’ve heard NGC 404 referred to as the Phantom Galaxy

So would that be the galaxy in George Lucas’ STAR WARS series? It is far, far away (at least *I* consider 11 million LY far, far away).

J/P=?

]]> By: Tom English http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144203 Tom English Tue, 30 Dec 2008 22:07:41 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144203 I've heard this object referred to as "Komorowski's Comet." Supposedly an amateur astronomer happened upon it one night, and after consulting his sky atlas and not finding an object there, initiated contacts with professionals to confirm his "discovery." I've forgotten the details of the story, but the school in NC where I used to teach owned one of Komorowski's telescopes, and I was told the tale by members of an area astronomy club. What was most memorable about the story was the last line: "...later his wife shot him." Presumably not about the comet misidentification. I’ve heard this object referred to as “Komorowski’s Comet.” Supposedly an amateur astronomer happened upon it one night, and after consulting his sky atlas and not finding an object there, initiated contacts with professionals to confirm his “discovery.” I’ve forgotten the details of the story, but the school in NC where I used to teach owned one of Komorowski’s telescopes, and I was told the tale by members of an area astronomy club. What was most memorable about the story was the last line: “…later his wife shot him.” Presumably not about the comet misidentification.

]]> By: IVAN3MAN http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144200 IVAN3MAN Tue, 30 Dec 2008 21:44:49 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144200 [pedant] According to Wikipedia, at least two techniques have been used to measure distances to <b>NGC 404</b>. The infrared surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. Using this technique in 2003, the distance measured is 9.9 ± 0.5 Mly (3.03 ± 0.15 Mpc). However, <b>NGC 404</b> is close enough that red super-giants can be imaged as individual stars. The light from these stars, in comparison to similar stars within the Milky Way galaxy, enables direct measurement of the distance to the galaxy. This method is referred to as the tip of the red giant branch (TRGB) method. The estimated distance to <b>NGC 404</b> using this technique is 10.0 ± 1.2 Mly (3.1 ± 0.4 Mpc). Averaged together, these distance measurements give a distance estimate of 10.0 ± 0.7 Mly (3.07 ± 0.21 Mpc) or approximately 10,300,000 light-years. Click on my name for the link to the Wikipedia article. [/pedant] [pedant]

According to Wikipedia, at least two techniques have been used to measure distances to NGC 404. The infrared surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. Using this technique in 2003, the distance measured is 9.9 ± 0.5 Mly (3.03 ± 0.15 Mpc).

However, NGC 404 is close enough that red super-giants can be imaged as individual stars. The light from these stars, in comparison to similar stars within the Milky Way galaxy, enables direct measurement of the distance to the galaxy. This method is referred to as the tip of the red giant branch (TRGB) method. The estimated distance to NGC 404 using this technique is 10.0 ± 1.2 Mly (3.1 ± 0.4 Mpc). Averaged together, these distance measurements give a distance estimate of 10.0 ± 0.7 Mly (3.07 ± 0.21 Mpc) or approximately 10,300,000 light-years.

Click on my name for the link to the Wikipedia article.

[/pedant]

]]> By: KC http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144188 KC Tue, 30 Dec 2008 21:01:07 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144188 I've heard NGC 404 referred to as the Phantom Galaxy (a name which these days is applied more to M74 than NGC 404). I think its an appropriate nickname as you really have to use averted vision to see it. I’ve heard NGC 404 referred to as the Phantom Galaxy (a name which these days is applied more to M74 than NGC 404). I think its an appropriate nickname as you really have to use averted vision to see it.

]]> By: Astronomynut http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144184 Astronomynut Tue, 30 Dec 2008 20:50:56 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144184 NGC 404 is easily seen in a small telescope. It lies just far enough away from Mirach to be able to slide the bright star out of the field of view, and there it shines brightly. In my 17.5", from a dark sky site, it's really bright. Not a lot of detail, but worth taking a look. I think it's on the Herschel 400 list. NGC 404 is easily seen in a small telescope. It lies just far enough away from Mirach to be able to slide the bright star out of the field of view, and there it shines brightly. In my 17.5″, from a dark sky site, it’s really bright. Not a lot of detail, but worth taking a look. I think it’s on the Herschel 400 list.

]]> By: Larian LeQuella http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144180 Larian LeQuella Tue, 30 Dec 2008 20:42:49 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144180 I keep getting a song stuck in my head reading this. I'll resist the urge to post the entire lyrics to Manfred Mann's Earth Band <I>"Blinded by the light"</I> though. I keep getting a song stuck in my head reading this. I’ll resist the urge to post the entire lyrics to Manfred Mann’s Earth Band “Blinded by the light” though.

]]> By: Thor http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/comment-page-1/#comment-144173 Thor Tue, 30 Dec 2008 20:21:35 +0000 http://blogs.discovermagazine.com/badastronomy/2008/12/30/the-ghost-of-mirach/#comment-144173 Good call on the 404. Good call on the 404.

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