Starship Asterisk*

NGC 206 and the Star Clouds of Andromeda

Explanation: The large stellar association cataloged as NGC 206 is nestled within the dusty arms of the neighboring Andromeda galaxy along with the galaxy's pinkish star-forming regions. Also known as M31, the spiral galaxy is a mere 2.5 million light-years away. NGC 206 is found right of center in this sharp and detailed close-up of the southwestern extent of Andromeda's disk. The bright, blue stars of NGC 206 indicate its youth. In fact, its youngest massive stars are less than 10 million years old. Much larger than the open or galactic clusters of young stars in the disk<a/> of our Milky Way galaxy, <a href="http://messier.seds.org/more/m031_n206.html">NGC 206 spans about 4,000 light-years. That's comparable in size to the giant stellar nurseries NGC 604 in nearby spiral M33 and the Tarantula Nebula in the Large Magellanic Cloud.

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I love today's APOD! It's gorgeous! Look at the colors!

APOD Robot wrote:
Much larger than the open or galactic clusters of young stars in the disk of our Milky Way galaxy, NGC 206 spans about 4,000 light-years. That's comparable in size to the giant stellar nurseries NGC 604 in nearby spiral M33 and the Tarantula Nebula in the Large Magellanic Cloud.

All right, but Andromeda as a whole is a far cry from being similar to M33 or the Large Magellanic Cloud, certainly when it comes to young stars and star formation!


NGC 206 in Andromeda is certainly impressive. We don't have anything similar in the Milky Way, to the best of my knowledge. Maybe M24? But it's not the same thing, is it? According to Wikipedia, M24 is only 600 light-years wide, which is a far cry from the 4,000 light-years of NGC 206. And it is not nearly as full of brilliant bright blue stars.


However, Andromeda is nevertheless a quite yellow galaxy. It is actually just a little bit bluer than giant elliptical galaxy M86:


When it comes to the B-V index (i.e., how "blue" the galaxy is overall), there is just a tiny difference between Andromeda and M86. Admittedly the difference is larger when it comes to the U-B index, which shows how ultraviolet a galaxy is.

Still, Andromeda is a yellow galaxy sporting a large blue and pink "jewelry blob" of star clusters and nebulosity in the region of NGC 206!



As for NGC 206, I read somewhere that it formed in this particular place because this is where two dust lanes meet in Andromeda. Can't say I can see two dust lanes there myself, but at least there is a big fat dark dust cloud to the left (east) of NGC 206.

Ann

So, Andromeda is 2.5 Mly away, but NGC 206 is 3 Mly away? Perhaps if the near edge of Andromeda is at 2.5 Mly and NGC 206 is in the very far edge, and Andromeda is taken to be about 500 Kly wide (using a very expanded size estimate that includes sparse halo stars). But that can't be right judging by Ann's image above showing NGC 206's position within Andromeda, and assuming that the "bottom" edge is the nearer edge.

johnnydeep wrote: ↑Wed Apr 12, 2023 8:40 pm So, Andromeda is 2.5 Mly away, but NGC 206 is 3 Mly away? Perhaps if the near edge of Andromeda is at 2.5 Mly and NGC 206 is in the very far edge, and Andromeda is taken to be about 500 Kly wide (using a very expanded size estimate that includes spares halo stars). But that can't be right judging by Ann's image above showing NGC 206's position within Andromeda, and assuming that the "bottom" edge is the nearer edge.

Wikipedia wrote:

The Andromeda Galaxy (IPA: /ænˈdrɒmɪdə/), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about 46.56 kiloparsecs (152,000 light-years) approximately 765 kpc (2.5 million light-years) from Earth and the nearest large galaxy to the Milky Way.

Exactly so, Johnny. According to Wikipedia, the distance to Andromeda is some 2.5 million light-years, and the diameter of Andromeda is "only" 152,000 light-years. Since NGC 206 resides in the disk of Andromeda, there is no way that it can be 500,000 light-years farther away from us than "Andromeda proper".


This is the correct "north is up" position of Andromeda in our night skies:


There are surprisingly few pictures that show Andromeda positioned like this. The NOIRLab picture above was obtained using one blue, one cyan and one red-orange filter, 435 nm, ███, 480 nm, ███, and 625 nm, ███, giving the picture a bluish cast. Note that you can faintly make out NGC 206 at lower right.

Anyway, this made me think - do we ever see spiral galaxies end on? We must do, but I can't think of a single one. Come to think of it, if they are round-ish anyway, they can't have narrow ends in the same way as if they were shaped as bars. So I guess they just look like flat pancakes, because of their arms.

In the picture below is the semi-flat pancake of NGC 7331, "standing up" in a fashion somewhat similar to Andromeda. Which side is closer to us? Actually, in NGC 7331, you can actually see which side is nearest. Surely you can too?


But what would the galaxy in the lower left panel below look like if we saw it end on?


Ann

Thanks Ann. PS - for some reason my account lost the setting that sends me an email whenever someone replies to a post I've posted to or that I've subscribed to, and I can't get find how to fix that.

Currently I have these settings: