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Galaxies in the River

Explanation: Large galaxies grow by eating small ones. Even our own galaxy practices galactic cannibalism, absorbing small galaxies that get too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus (The River). Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531, a struggle the smaller galaxy will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. Nicely detailed in this sharp image, the NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.

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So then, what if a larger galaxy than the Milky Way comes and gobbles us up? Just kiddin', but just saying....

The distortions of the larger galaxy don't seem to match either the position, location and apparent lack of distortions in the smaller galaxy. The smaller galaxy seems to be in a strange perpendicular-like position over the center of the larger galaxy - as if it were dropping into the center of the larger like a rock .....

moonstruck wrote:So then, what if a larger galaxy than the Milky Way comes and gobbles us up? Just kiddin', but just saying....

What if? It's going to happen, didn't you know?



The Andromeda Galaxy is coming!!!

Ann

biddie67 wrote:The distortions of the larger galaxy don't seem to match either the position, location and apparent lack of distortions in the smaller galaxy. The smaller galaxy seems to be in a strange perpendicular-like position over the center of the larger galaxy - as if it were dropping into the center of the larger like a rock .....

If the smaller galaxy is elliptical in shape and fairly compact, it wouldn't necessarily be strongly distorted.

Here is a link to an ultraviolet image of interacting galaxies NGC 1512 (the larger one) and 1510 (the smaller one). Note how the blue arms of NGC 1512 seem to reach out to NGC 1510, while NGC 1510 looks undisturbed.

http://www.galex.caltech.edu/media/glx2 ... img03.html

Also look at this infrared image of galaxy NGC 1097. You can see how the dusty (pink) arms of 1097 wrap themselves around the small dust-free blue-looking elliptical galaxy. The small elliptical looks undisturbed.

http://www.scienceandreason.net/images/NGC_1097.jpg

Ann

Speculation also holds that the Sagittarius Dwarf was once pulled through the Milky Way disk very close to our Sun's current location.

So; is it possible that the sun may have been captured from the Sagittarius Dwarf?

Thanks, Ann - ultraviolet sure reveals more of the story ... gravity is certainly a determined and persistant entity!

Ann wrote:

moonstruck wrote:So then, what if a larger galaxy than the Milky Way comes and gobbles us up? Just kiddin', but just saying.... :?

What if? It's going to happen, didn't you know?
The Andromeda Galaxy is coming!!!

There's a reasonable chance that the Milky Way and Andromeda (which are similarly sized) will merge, but it isn't certain. We don't have a good understanding of the velocity of Andromeda- we know very accurately the component in our direction, but not the tangential component. So it is quite possible that our two galaxies will simply swing around each other. If that happens, there will be tidal distortion that alters both galaxies.

Given the complexity of orbits in the Local Group, a future collision seems inevitable even if it doesn't happen when the two are closest in 4 or 5 billion years. But that collision might be many billions of years away.

moonstruck wrote:So then, what if a larger galaxy than the Milky Way comes and gobbles us up? Just kiddin', but just saying.... :?

Then we'd find ourselves living in a larger galaxy. We may well merge with Andromeda, which is about the same size as the Milky Way, or slightly larger, in a few billion years. That's the soonest this could happen, and by that time the Earth will not be supporting human life. So we won't have the opportunity to enjoy the interesting new night sky.

Whew, Ann had me worried there for a minute until Chris came along.

moonstruck wrote:Whew, Ann had me worried there for a minute until Chris came along.

Yeah, I think the Sun swallowing the Earth is probably more of an immediate concern than any imminent collision with Andromeda.

bystander wrote:

moonstruck wrote:Whew, Ann had me worried there for a minute until Chris came along. :wink:

Yeah, I think the Sun swallowing the Earth is probably more of an immediate concern than any imminent collision with Andromeda.

Long time scales aside, we'd probably not experience any unpleasant effects from a collision between the Milky Way and Andromeda. I can't say the same for the Sun expanding out to the orbit of the Earth!

I used to worry about the Moon crashing into the Earth, but I now know it's more likely to go flying off into space, what a relief.

bystander wrote:I used to worry about the Moon crashing into the Earth, but I now know it's more likely to go flying off into space, what a relief.

The moon might somehow attain an extra 0.425 km/s to escape from the earth but it is highly unlikely that it would attain an extra 12.35 km/s on top of that to escape from the earth's orbit. Ergo, any escaped moon would return to its mother earth on a periodic basis (and with a vengeance).

So the moon is retreating about 4 centimeters per year; or about 13 feet per century! That's slow enough for me. I don't want to hurry it any.

neufer wrote:The moon might somehow attain an extra 0.425 km/s to escape from the earth but it is highly unlikely that it would attain an extra 12.35 km/s on top of that to escape from the earth's orbit. Ergo, any escaped moon would return to its mother earth on a periodic basis (and with a vengeance).

Oh,no! Something else to worry about. Just when I was beginning to feel safe.

Rats..woe is me...

Chris said:

There's a reasonable chance that the Milky Way and Andromeda (which are similarly sized) will merge, but it isn't certain.

So it isn't certain that the Milky Way and Andromeda will merge.

In the same post, however, Chris also said:

Given the complexity of orbits in the Local Group, a future collision seems inevitable

So it isn't certain that the Milky Way and Andromeda will merge, even though a collision seems inevitable? What exactly are you saying? The Milky Way and Andromeda will collide, but they will not necessarily merge? Or was that a creative way of saying that I was wrong, even if the point I made was the correct one?

Ann

Ann wrote:

Chris wrote:There's a reasonable chance that the Milky Way and Andromeda (which are similarly sized) will merge, but it isn't certain.

So it isn't certain that the Milky Way and Andromeda will merge.

The Sun orbits the center of the Milky Way 25,000 light years away with a speed of 220 km/s.

Hence, at the distance of Andromeda (2,500,000 light years away) the escape velocity is probably on the order of ~ 60 km/s
{i.e., 60 km/s ~ 220 km/s x sqrt [(2 x full mass of both galaxies)/(100 x mass of Milky Way inside the Sun)]}

If Andromeda had a blueshift of ~300 km/s (>> 60 km/s) it would easily escape from the Milky Way.

Since Andromeda has a redshift of ~300 km/s it will probably pass through (or by)
the Milky Way without merging and continue on to escape out the other side.

I certainly realize that the Milky Way and Andromeda may not merge during their first close encounter. That isn't what I was trying to say, either.

My understanding is that the Milky Way and Andromeda will keep dancing around each other, their orbits shrinking, until they eventually merge.

Ann

Ann wrote:I certainly realize that the Milky Way and Andromeda may not merge during their first close encounter. That isn't what I was trying to say, either. My understanding is that the Milky Way and Andromeda will keep dancing around each other, their orbits shrinking, until they eventually merge.

And what I'm saying is that aint gonna happen...Andromeda has way too much speed to be anything other than a hit & run driver.

(There will be a lot of broken glass all over the place, of course.)

Ann wrote:So it isn't certain that the Milky Way and Andromeda will merge, even though a collision seems inevitable? What exactly are you saying?

I'm saying that while the Andromeda galaxy has a velocity with a significant component directed towards the Milky Way, and there's a reasonable chance of a collision in 4 or 5 billion years, that collision isn't certain. When people talk about the two galaxies colliding, they are usually referring to this particular collision- that is, the one inferred from the currently observed motion.

Orbits in multiple body systems are chaotic, so if this collision doesn't occur, the galaxies will still be in orbit around each other, and it is statistically likely they will eventually collide. It is impossible to predict when, however, and there will be many times that the two galaxies will be getting farther apart. They won't be orbiting such that they get closer and closer together over time.