by Ann » Fri Aug 24, 2018 4:50 am
APOD Robot wrote:
Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old.
I beg to differ, in my amateur way.
I certainly don't question the age estimates for M20 and M21. I t goes without saying that they formed at different times. But the fact that they are not the same age doesn't have to mean they aren't connected. At least I don't think so.
Take a look at the following wide-angle picture of M8, M20 and M21:
Look at the "skyscape" surrounding M8, M20 and M21. Look at the excess of scattered bright blue stars in the region surrounding M20 and M21. These scattered blue stars seem to form a "bridge" between M20 and M21.
Isn't it possible that the formation of M21 led to repercussions in the surrounding dusty interstellar medium that pervades this entire region, repercussions that compressed the dust cloud that turned into the Trifid Nebula? Alternatively, isn't it possible that both M21 and M20 owe their formation to some other upheaval that has happened in this general region within the last ten million years or so?
M20 and M21 sure
look connected. In any case, there is a lot going on in this part of the sky, and this region isn't at all "typical" of the Milky Way when it comes to the number and brightness of its nebulas or the number and brightness and youth of its clusters.
Ann
[quote]APOD Robot wrote:
Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old.
[/quote]
I beg to differ, in my amateur way. :wink:
I certainly don't question the age estimates for M20 and M21. I t goes without saying that they formed at different times. But the fact that they are not the same age doesn't have to mean they aren't connected. At least I don't think so.
Take a look at the following wide-angle picture of M8, M20 and M21:
[float=left][img2]https://c1.staticflickr.com/8/7697/27489192892_fd5caa6311_b.jpg[/img2][c][size=85]M8, M20 and M21. Photo: Daniel Chang,
https://www.flickr.com/photos/daniel_chang/27489192892[/size][/c][/float] Look at the "skyscape" surrounding M8, M20 and M21. Look at the excess of scattered bright blue stars in the region surrounding M20 and M21. These scattered blue stars seem to form a "bridge" between M20 and M21.
Isn't it possible that the formation of M21 led to repercussions in the surrounding dusty interstellar medium that pervades this entire region, repercussions that compressed the dust cloud that turned into the Trifid Nebula? Alternatively, isn't it possible that both M21 and M20 owe their formation to some other upheaval that has happened in this general region within the last ten million years or so?
M20 and M21 sure [i]look[/i] connected. In any case, there is a lot going on in this part of the sky, and this region isn't at all "typical" of the Milky Way when it comes to the number and brightness of its nebulas or the number and brightness and youth of its clusters.
Ann