Starship Asterisk*

Exploring the Antennae

Explanation: Some 60 million light-years away in the southerly constellation Corvus, two large galaxies are colliding. Stars in the two galaxies, cataloged as NGC 4038 and NGC 4039, very rarely collide in the course of the ponderous cataclysm that lasts for hundreds of millions of years. But the galaxies' large clouds of molecular gas and dust often do, triggering furious episodes of star formation near the center of the cosmic wreckage. Spanning over 500 thousand light-years, this stunning view also reveals new star clusters and matter flung far from the scene of the accident by gravitational tidal forces. The remarkably sharp ground-based image includes narrowband data that highlights the characteristic red glow of atomic hydrogen gas in star-forming regions. The suggestive overall visual appearance of the extended arcing structures gives the galaxy pair its popular name - The Antennae.

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It's always nice to see a new picture of the Antennae Galaxies, and Bernard Miller's image is a very fine example of what amateurs can achieve.

What I like best about Miller's image is how it underscores the difference between the gas-rich galaxy NGC 4038 (at top in his image) and NGC 4039. Note how yellow NGC 4039 is. There is not a lot of star formation going on in that galaxy at all, whereas, by contrast, NGC 4038 is "exploding" with star formation.

I remember reading that most of the star formation in the Antennae Galaxies is actually taking place in the huge dark dust cloud between the two galaxies. So I went looking for an infrared image of the Antennae, which should reveal more of the star formation going on there, and I was a bit disappointed. The infrared Gemini GeMS/GSAORI IR image does not reveal a whole lot more star formation than what is more or less obvious in the Hubble image. Admittedly a few more sources can be seen.























The picture at left was made with the help of great professional telescopes, which is why more details can be seen in it than in Bernard Miller's image.

In the image at left, note the tail emanating from NGC 4038. The tail extends to the left and down. Note that at the end of it, star clusters have formed, which may later turn into dwarf galaxies.

In the image at right, I would guess that the dark blue stuff seen in the tail is (neutral) hydrogen gas, although I'm not sure. Note that we don't see any gas escaping from NGC 4039, the gas-poor galaxy.

Imagine if NGC 4038 and 4039 both had been gas-rich. What starbursting cosmic train wreck it would have been.

Ann

We now KNOW that many stars have planets, pushing the Drake Equation further towards the likelihood of alien life. So there are probably planets around the stars of NGC 4038/9, and possibly life.
Or were. OK, the stars are too far apart to collide, but the gas clouds do with consequent material and radiation outputs. Could life survive the areas of "furious" star formation? Would an event like that sterilise a galaxy?
John

Bernard Miller's Antennae makes a very good photo!

JohnD wrote: ↑Sat Mar 27, 2021 10:50 am
We now KNOW that many stars have planets, pushing the Drake Equation further towards the likelihood of alien life. So there are probably planets around the stars of NGC 4038/9, and possibly life.

Or were. OK, the stars are too far apart to collide, but the gas clouds do with consequent material and radiation outputs. Could life survive the areas of "furious" star formation? Would an event like that sterilise a galaxy?

It would certainly kill off independent George, at least.

neufer wrote: ↑Sat Mar 27, 2021 3:36 pm

Click to play embedded YouTube video.

JohnD wrote: ↑Sat Mar 27, 2021 10:50 am
We now KNOW that many stars have planets, pushing the Drake Equation further towards the likelihood of alien life. So there are probably planets around the stars of NGC 4038/9, and possibly life.

Or were. OK, the stars are too far apart to collide, but the gas clouds do with consequent material and radiation outputs. Could life survive the areas of "furious" star formation? Would an event like that sterilise a galaxy?

It would certainly kill off independent George, at least.

Cute. "Worlds are Colliding!" indeed (but probably not that much in the case of worlds orbiting stars in the Antennae Galaxies). Coincidentally, due to the capriciousness of the YouTube recommendations algorithm, I had just watched this same clip a few days ago.

JohnD wrote: ↑Sat Mar 27, 2021 10:50 am We now KNOW that many stars have planets, pushing the Drake Equation further towards the likelihood of alien life. So there are probably planets around the stars of NGC 4038/9, and possibly life.
Or were. OK, the stars are too far apart to collide, but the gas clouds do with consequent material and radiation outputs. Could life survive the areas of "furious" star formation? Would an event like that sterilise a galaxy?
John

I don't think radiation would be much of an issue over most of the volume. What would be problem, though, is near misses (near hits?) A couple of stars passing within a light year or so of each other could result in a bombardment of the inner systems with comets, or even perturb planetary orbits... something that all but the simplest life is likely to be extremely sensitive to.

Ann wrote: ↑Sat Mar 27, 2021 7:35 am In the image at left, note the tail emanating from NGC 4038. The tail extends to the left and down. Note that at the end of it, star clusters have formed, which may later turn into dwarf galaxies.
In the image at right, I would guess that the dark blue stuff seen in the tail is (neutral) hydrogen gas, although I'm not sure. Note that we don't see any gas escaping from NGC 4039, the gas-poor galaxy.
Imagine if NGC 4038 and 4039 both had been gas-rich. What starbursting cosmic train wreck it would have been.
Ann

What do they call a dwarf of known origin? Something ibn NGC 4038 ?

VictorBorun wrote: ↑Sun Mar 28, 2021 11:47 am

Ann wrote: ↑Sat Mar 27, 2021 7:35 am In the image at left, note the tail emanating from NGC 4038. The tail extends to the left and down. Note that at the end of it, star clusters have formed, which may later turn into dwarf galaxies.
In the image at right, I would guess that the dark blue stuff seen in the tail is (neutral) hydrogen gas, although I'm not sure. Note that we don't see any gas escaping from NGC 4039, the gas-poor galaxy.
Imagine if NGC 4038 and 4039 both had been gas-rich. What starbursting cosmic train wreck it would have been.
Ann

What do they call a dwarf of known origin? Something ibn NGC 4038 ?

Not quite sure what you're asking, but I do know that giant elliptical galaxy M60 has a tiny compact companion galaxy that is called M60-UCD1. UCD1 means Ultra Compact Dwarf 1, and M60 means that this dwarf is a satellite of M60.

So I guess it would be possible for a dwarf of NGC 4038 to be named after NGC 4038, but I'm not aware of any dwarf galaxies of NGC 4038 that have received names or designations.

Ann

VictorBorun wrote: ↑Sun Mar 28, 2021 11:47 am What do they call a dwarf of known origin? Something ibn NGC 4038 ?

A gnome?

Ann wrote: ↑Sun Mar 28, 2021 1:08 pm giant elliptical galaxy M60 has a tiny compact companion galaxy that is called M60-UCD1. UCD1 means Ultra Compact Dwarf 1, and M60 means that this dwarf is a satellite of M60.
So I guess it would be possible for a dwarf of NGC 4038 to be named after NGC 4038, but I'm not aware of any dwarf galaxies of NGC 4038 that have received names or designations.
Ann

a satellite of X does not have to be a child of X; it may be a sibling of X or a comlete stranger

JohnD wrote: ↑Sun Mar 28, 2021 7:53 pm

VictorBorun wrote: ↑Sun Mar 28, 2021 11:47 am What do they call a dwarf of known origin? Something ibn NGC 4038 ?

A gnome?

gnome can't be used in a phrase like a gnome of X

I think "A gnome of a galaxy" would mean something other than a seperated patch of a galaxy

VictorBorun wrote: ↑Thu Apr 01, 2021 11:06 am

JohnD wrote: ↑Sun Mar 28, 2021 7:53 pm

VictorBorun wrote: ↑Sun Mar 28, 2021 11:47 am What do they call a dwarf of known origin? Something ibn NGC 4038 ?

A gnome?

gnome can't be used in a phrase like a gnome of X

I think "A gnome of a galaxy" would mean something other than a seperated patch of a galaxy

Of course that form of words is viable:
The Gnomes of Zurich
The Gnome of Sofia ( a book)
The Gnome of Essex (Keith Fletcher)
The Gnome of the harzberg, or Bertha (an opera)
ETc.ETc.
And there are "gnome galaxies" - https://www.freepressjournal.in/infogra ... blackholes