by Ann » Fri Jul 19, 2013 6:31 am
FLPhotoCatcher wrote:A bit off topic, but I couldn't help but notice that the satellite galaxy in the first picture Ann posted (NGC 1232) looks very much like the Large Magellanic Cloud.
I agree that the satellite galaxy, NGC 1232A, looks quite a bit like the Large Magellanic Cloud. The galaxy is strongly barred, just like LMG, and it has a lot of "blue fluff" flying around the bar. You can see NGC 1232A better
NGC 1232A used to cause astronomers a lot of headache, because its recession velocity appeared to be much larger than the recession velocity of NGC 1232 itself. This would imply that the satellite galaxy wasn't a satellite galaxy at all, but a distant background galaxy. Of course there are several problems with this scenario.
NGC 1232A is extremely similar in apparent color to NGC 1232 proper, and
its "blue clumps" are almost exactly the same size as the blue clumps of the larger galaxy. Also NGC 1232 is located almost exactly at the end point of a long spiral arm of NGC 1232, suggesting that NGC 1232A had somehow been "torn off" its parent galaxy.
We may compare the appearance of NGC 1232 and NGC 1232A with the appearance of
NGC 1309 and a striking but unnamed barred galaxy apparently located close to it. We can see, at a glance, that the strikingly barred blue galaxy to the upper left of NGC 1309 is a background galaxy. First of all, NGC 1309 itself has a lot of star formation and broad thick arms, which suggests that NGC 1309 isn't a very large galaxy. According to my software, NGC 1309 is about equally luminous as the Milky Way, whereas NGC 1232, with its long thin arms, is more than twice as luminous as our own galaxy.
But the barred blue galaxy to the upper left of NGC 1309 has a shape similar to
NGC 7479. NGC 7479 is more than twice as luminous as the Milky Way, according to my software. To me, that strongly suggests that the barred galaxy seen in the same field of view as NGC 1309 is big, too, and definitely bigger than NGC 1309 itself. Also the "blue clumps" of the barred galaxy next to NGC 1309 are generally smaller than the blue clumps of NGC 1309. At high magnification, the smaller galaxy looks coarser than NGC 1309. Conclusion: the blue barred galaxy to the upper left of NGC 1309 is a background object, not a satellite galaxy.
But NGC 1232A shows every sign of being a satellite galaxy of NGC 1232. And when I checked my software today, the recession velocity of NGC 1232A is now thought to be very similar to the recession velocity of 1232 itself. Problem solved!
Ann
[quote="FLPhotoCatcher"]A bit off topic, but I couldn't help but notice that the satellite galaxy in the first picture Ann posted (NGC 1232) looks very much like the Large Magellanic Cloud.[/quote]
I agree that the satellite galaxy, NGC 1232A, looks quite a bit like the Large Magellanic Cloud. The galaxy is strongly barred, just like LMG, and it has a lot of "blue fluff" flying around the bar. You can see NGC 1232A better
NGC 1232A used to cause astronomers a lot of headache, because its recession velocity appeared to be much larger than the recession velocity of NGC 1232 itself. This would imply that the satellite galaxy wasn't a satellite galaxy at all, but a distant background galaxy. Of course there are several problems with this scenario. [url=http://www.discordancyreport.com/wp-content/uploads/2011/10/ngc1232.jpg]NGC 1232A is extremely similar in apparent color to NGC 1232 proper[/url], and [url=http://1024x.net/wallpapers/90b/Spiral_Galaxy_NGC_1232_In_Eridanus.jpg]its "blue clumps" are almost exactly the same size as the blue clumps of the larger galaxy[/url]. Also NGC 1232 is located almost exactly at the end point of a long spiral arm of NGC 1232, suggesting that NGC 1232A had somehow been "torn off" its parent galaxy.
We may compare the appearance of NGC 1232 and NGC 1232A with the appearance of [url=http://www.mcleanclan.net/BrianMcLean/photo_gallery/Astronomy/ps20_4x6.jpg]NGC 1309 and a striking but unnamed barred galaxy apparently located close to it.[/url] We can see, at a glance, that the strikingly barred blue galaxy to the upper left of NGC 1309 is a background galaxy. First of all, NGC 1309 itself has a lot of star formation and broad thick arms, which suggests that NGC 1309 isn't a very large galaxy. According to my software, NGC 1309 is about equally luminous as the Milky Way, whereas NGC 1232, with its long thin arms, is more than twice as luminous as our own galaxy.
But the barred blue galaxy to the upper left of NGC 1309 has a shape similar to [url=https://upload.wikimedia.org/wikipedia/commons/thumb/9/94/NGC_7479_HST.jpg/300px-NGC_7479_HST.jpg]NGC 7479[/url]. NGC 7479 is more than twice as luminous as the Milky Way, according to my software. To me, that strongly suggests that the barred galaxy seen in the same field of view as NGC 1309 is big, too, and definitely bigger than NGC 1309 itself. Also the "blue clumps" of the barred galaxy next to NGC 1309 are generally smaller than the blue clumps of NGC 1309. At high magnification, the smaller galaxy looks coarser than NGC 1309. Conclusion: the blue barred galaxy to the upper left of NGC 1309 is a background object, not a satellite galaxy.
But NGC 1232A shows every sign of being a satellite galaxy of NGC 1232. And when I checked my software today, the recession velocity of NGC 1232A is now thought to be very similar to the recession velocity of 1232 itself. Problem solved! :D
Ann