by Ann » Wed Jan 08, 2014 1:00 am
MarkBour wrote:Beautiful image. I liked starsurfer's characterization: "... glittering sapphires on the golden galactic beach".
As usual, here's a post full of questions ...
I assume the blue-ish stars are the cluster, and are at about 1000 light-years away, as the caption described. But around the core of the cluster, one sees other blue stars, smaller and spreading far and wide. Also, there are a few large yellow-hued stars in the image, and then again, some smaller, and it seems that for the yellows at least, the field of view holds a vast number of them.
Q1: Are the large yellow stars as close as the large blue stars?
Q2: Are the large yellow stars part of this cluster?
Q3: I'm assuming most of these small yellow dots are stars in the further part,
perhaps a spiral arm of the Milky Way, and I am guessing they are some
10-20 times as far away as the M7 cluster. Is that correct?
Q4: I wonder about them. As dense as they appear, are they actually separated on average by
greater distances than the stars in the M7 cluster?
And finally, suppose an instrument like the Kepler space telescope were pointed at this region. Would it be able to watch these stars for light variations, to hunt for planets, or is there just too much light coming from this area for it to work? I had heard that Kepler had been pointed at a relatively dark area, with fewer stars in view.
Yes, the three largest yellow stars are as close as the large blue stars, and they are members of the same cluster. They have the same parallax as the large blue stars, which shows that they are as far away as the blue stars, and they have the same proper motion as the large blue stars, which means that they move in the same direction across the sky as the large blue stars.
The small yellow dots are parts of
the bulge of the Milky Way. They may indeed be 10-20 times as far away as cluster M7. Not all the stars that we see in the bulge are at the same distance from us either. The stars that appear to form a dense wall of stars are actually superimposed on one another at various distances from us.
The stars in the bulge of the Milky Way are relatively close together. Take a look at
this image of the Milky Way. The bulge is the brightest-looking part of it. Why is it so bright? Because the stars in it are very bright themselves? No, most of the stars in the bulge are quite faint. The bulge is bright because it contains such a large number of stars, and the average distance between them is smaller than the distance between stars in the disk.
However, stars in a cluster are also closer to one another than the average stars in the disk. However, cluster M7 is larger than it immediately appears to be, and the stars in the outskirts of the cluster are not as close together as the stars nearer the cluster center. When it comes to the average separation between the stars in the bulge (which varies with the distance from the galactic core, remember) and the average separation between the stars in M7, I'm afraid I can't help you.
Ann
[quote="MarkBour"]Beautiful image. I liked starsurfer's characterization: "... glittering sapphires on the golden galactic beach".
As usual, here's a post full of questions ...
I assume the blue-ish stars are the cluster, and are at about 1000 light-years away, as the caption described. But around the core of the cluster, one sees other blue stars, smaller and spreading far and wide. Also, there are a few large yellow-hued stars in the image, and then again, some smaller, and it seems that for the yellows at least, the field of view holds a vast number of them.
Q1: Are the large yellow stars as close as the large blue stars?
Q2: Are the large yellow stars part of this cluster?
Q3: I'm assuming most of these small yellow dots are stars in the further part,
perhaps a spiral arm of the Milky Way, and I am guessing they are some
10-20 times as far away as the M7 cluster. Is that correct?
Q4: I wonder about them. As dense as they appear, are they actually separated on average by
greater distances than the stars in the M7 cluster?
And finally, suppose an instrument like the Kepler space telescope were pointed at this region. Would it be able to watch these stars for light variations, to hunt for planets, or is there just too much light coming from this area for it to work? I had heard that Kepler had been pointed at a relatively dark area, with fewer stars in view.[/quote]
Yes, the three largest yellow stars are as close as the large blue stars, and they are members of the same cluster. They have the same parallax as the large blue stars, which shows that they are as far away as the blue stars, and they have the same proper motion as the large blue stars, which means that they move in the same direction across the sky as the large blue stars.
The small yellow dots are parts of [url=http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap23/6th/23_01Figurea-F.jpg]the bulge of the Milky Way[/url]. They may indeed be 10-20 times as far away as cluster M7. Not all the stars that we see in the bulge are at the same distance from us either. The stars that appear to form a dense wall of stars are actually superimposed on one another at various distances from us.
The stars in the bulge of the Milky Way are relatively close together. Take a look at [url=http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2010/11/milkyway.jpg]this image of the Milky Way.[/url] The bulge is the brightest-looking part of it. Why is it so bright? Because the stars in it are very bright themselves? No, most of the stars in the bulge are quite faint. The bulge is bright because it contains such a large number of stars, and the average distance between them is smaller than the distance between stars in the disk.
However, stars in a cluster are also closer to one another than the average stars in the disk. However, cluster M7 is larger than it immediately appears to be, and the stars in the outskirts of the cluster are not as close together as the stars nearer the cluster center. When it comes to the average separation between the stars in the bulge (which varies with the distance from the galactic core, remember) and the average separation between the stars in M7, I'm afraid I can't help you.
Ann