APOD: Arp 272 (2011 Sep 22)

[APOD Robot]

Arp 272

Explanation: Linking spiral arms, two large colliding galaxies are featured in this remarkable cosmic portrait constructed using image data from the Hubble Legacy Archive. Recorded in astronomer Halton Arp's Atlas of Peculiar Galaxies as Arp 272, the pair is otherwise known as NGC 6050 near center, and IC 1179 at upper right. A third galaxy, likely also a member of the interacting system, can be spotted above and left of larger spiral NGC 6050. They lie some 450 million light-years away in the Hercules Galaxy Cluster. At that estimated distance, the picture spans over 150 thousand light-years. Although this scenario does look peculiar, galaxy collisions and their eventual mergers are now understood to be common, with Arp 272 representing a stage in this inevitable process. In fact, the nearby large spiral Andromeda Galaxy is known to be approaching our own galaxy and Arp 272 may offer a glimpse of the far future collision between Andromeda and the Milky Way.

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[Beyond]

Like a three-ring circus, they're putting on quite a show. I wonder if they all have black holes?

[orin stepanek]

I take it that a 4th and maybe a 5th galaxy seen in the space is beyond the three that are merging and are not part of this scenario.

arp272HLA_pugh800.jpg (11.05 KiB) Viewed 5913 times

[steve b]

what would the nightsky look like from a planet on the periphery of one of the galaxies? does any one have a simulation?

[nstahl]

I looked at that and immediately thought The Scream.

Yet another great APOD.

[Jeauxyno1]

I note the use of the word "collision" for two galaxies coming together, but given huge distances between individuals stars do any stars actually collide during a galactic "collision". If the likelihood is small, the word "merge" seems preferrable to "collision", don't you agree?

[neufer]

I note the use of the word "collision" for two galaxies coming together, but given huge distances between individuals stars do any stars actually collide during a galactic "collision". If the likelihood is small, the word "merge" seems preferrable to "collision", don't you agree?

"Merge" doesn't work because the galaxies pass through each other. (I.e., Hit & Run)

The stars aren't colliding...just the galaxies. (And no one is merging.)

Collide, v. i. [L. collidere, collisum; col- + laedere to strike.]
To strike or dash against each other; to clash; as, the vessels collided; their interests collided.

[Guest]

I am not an astronomer, but I don't understand the very common claim that the Andromeda Galaxy will collide with our galaxy. Andromeda's blue doppler shift shows its component of motion toward us, but this does not show that it is coming directly at us. It may very well have an unmeasured component of motion that will cause it to miss our galaxy entirely. To determine that it is coming directly at us we would have to measure its proper motion and this cannot be done at the moment as far as I know.

Jim Shea

[neufer]

I am not an astronomer, but I don't understand the very common claim that the Andromeda Galaxy will collide with our galaxy. Andromeda's blue doppler shift shows its component of motion toward us, but this does not show that it is coming directly at us. It may very well have an unmeasured component of motion that will cause it to miss our galaxy entirely. To determine that it is coming directly at us we would have to measure its proper motion and this cannot be done at the moment as far as I know.

<<The Andromeda–Milky Way collision is a predicted galaxy collision that could possibly take place in approximately 3 to 5 billion years' time between the two largest galaxies in the Local Group—the Andromeda Galaxy and the Milky Way. There is, as yet, no way to know whether the possible collision is definitely going to happen or not. The radial velocity of the Andromeda galaxy with respect to the Milky Way can be measured by examining the Doppler shift of spectral lines from stars in the galaxy, but the transverse velocity cannot be directly measured. Thus, while it is known that the Andromeda galaxy is getting closer to the Milky Way by about 120 km/s, there is no way to tell whether it is going to collide or miss. The best indirect estimates of the transverse velocity indicate that it is less than 100 km/s. This suggests that the dark matter halos, although possibly not the actual disks, of the galaxies will collide.>>

[Ann]

APOD Robot wrote:

Linking spiral arms, two large colliding galaxies

I don't think that Arp 272 should be described as, first and foremost, two large colliding spiral galaxies. I think it can only be described as a three-galaxy system, likely consisting of one massive and two less massive galaxies.

Of the three galaxies making up this system, NGC 6050, with its large yellow bulge, is clearly the most massive. It reminds me of M81.

The galaxy at upper right, IC 1179, reminds me of NGC 7741. Like NGC 7741, IC 1179 has a long rather narrow bar, but the bar doesn't grow noticably brighter in the middle. It is just a long luminous ribbon, spouting broad bright spiral arms bursting with young blue stars.

I searched for a long time before I found something even remotely like the nameless third member of Arp 272. This third galaxy has a relatively bright bulge, which looks like a wind-blown distorted bar, with a considerable population of massive unstable stars. However, this third member of Arp 272 apparently lacks spiral arms altogether. The only galaxy I could find that is even remotely like it is the bulge of the starburst galaxy, NGC 1808.



Of course, these three galaxies are strongly entangled with one another, creatinga unique system. And speaking about this system being unique: A fourth, and possibly even a fifth, galaxy can be seen at eleven o'clock in this image, encircled by spiral arms from the brighter members of Arp 272. Can these two faint galaxies be physical parts of Arp 272? I don't feel able to offer a definite opinon, but I note that the two small galaxies appear to be slightly, but not very, reddened compared with the larger galaxies.

Thank you for this fascinating APOD! We have seen the Hubble image before, of course, but Martin Pugh's processing has certainly made the image even better.


Ann

[Anthony Barreiro]

I looked at that and immediately thought The Scream.

Yet another great APOD.

Me too. Maybe this multiple galaxy system is screaming because the components can't decide whether to collide, merge, or pass like ships in the night. We need a new catalogue of distant galaxies that look like Edvard Munch paintings. This would be listed as Munch 1.

[biddie67]

WOW!!! What a complexity of gravitational forces at work there. I wish that the action could be somehow sped up so we could see how it all resolved itself within our lifetimes.

I don't think that mathematical modeling could handle this adequately.

[biddie67]

In the comments about the apparent closing of distance between the Andromeda Galaxy and our galaxy, the phrase "transverse motion" was mentioned.

Does this mean a left-right component of motion and/or an up-down component of motion - something like in a 3 dimensional x-y-z axis where x represents motion towards us and y/z motion that can't be detected ??

Or vector stuff - as you can tell my math skills are pretty basic .....

[Chris Peterson]

I am not an astronomer, but I don't understand the very common claim that the Andromeda Galaxy will collide with our galaxy. Andromeda's blue doppler shift shows its component of motion toward us, but this does not show that it is coming directly at us. It may very well have an unmeasured component of motion that will cause it to miss our galaxy entirely. To determine that it is coming directly at us we would have to measure its proper motion and this cannot be done at the moment as far as I know.

That the two galaxies will ultimately collide is certain. What isn't certain (for the reason you identify) is whether that collision will happen on the current orbital segment (which would happen in a few billion years), or on another orbit altogether, which could place the collision tens of billions of years in the future.

[NoelC]

I don't think that mathematical modeling could handle this adequately.

I imagine it could with a sufficiently advanced computer.

Give it ten or twenty years. A hundred million core Intel Xeon will eat it for lunch.

-Noel

[SJoe]

WOW!!! What a complexity of gravitational forces at work there. I wish that the action could be somehow sped up so we could see how it all resolved itself within our lifetimes.

I don't think that mathematical modeling could handle this adequately.

This is definately a "lite" physics sim, but with a little time I'm sure it could be modeled.

http://universesandbox.com/

One of the simulations included with the program is the collision between the milky way and andromeda galaxy. If it happens.

[Burnham]

Why is it that one galixie will turning clock wise and the other counter clockwise?? OR is one upside right and the other up side down??

What effect determines the systems " spin" ?

[neufer]

Why is it that one galaxy will be turning clock wise and the other counter clockwise?? OR is one upside right and the other up side down??

What effect determines the systems " spin" ?

Residual (turbulent?) local angular momentum at the time the galaxies formed (not necessarily near each other).