APOD: The Diner at the Center of the Galaxy (2011 Dec 30)

[APOD Robot]

The Diner at the Center of the Galaxy

Explanation: The monster at the center of our Galaxy is about to get fed. Recent observations by the Very Large Telescopes indicate that a cloud of gas will venture too close to the supermassive black hole at the Galactic center. The gas cloud is being disrupted, stretched out, heated up, and some of it is expected to fall into the black hole over the next two years. In this artist's illustration, what remains of the blob after a close pass to the black hole is shown in red and yellow, arching out from the gravitational death trap to its right. The cloud's orbit is shown in red, while the orbits of central stars are shown in blue. The infalling nebula is estimated to contain several times the mass of our Earth, while the central black hole, thought to correspond to the radio source Sagittarius A*, contains about four million times the mass of our Sun. Once it falls in, nothing is expected to be heard from the doomed gas ever again.

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[bystander]

http://asterisk.apod.com/viewtopic.php?f=31&t=26180

[TNT]

The main course has arrived!

[Julie]

stunning pic and also an extemely interesting story!

[Boomer12k]

You do realize that this has taken place already. We do not see things in real time. We are about 26,000 light years from the Galactic Center, and so this event was over and done with 26,000 years ago, around 24,000 B.C.
Still pretty cool, as hopefully, WE WILL GET TO SEE SOMETHING WE WOULD NOT HAVE BEEN ABLE TO SEE BACK THEN!!!

:---[===] *

[Ann]

You do realize that this has taken place already. We do not see things in real time. We are about 26,000 light years from the Galactic Center, and so this event was over and done with 26,000 years ago, around 24,000 B.C.
Still pretty cool, as hopefully, WE WILL GET TO SEE SOMETHING WE WOULD NOT HAVE BEEN ABLE TO SEE BACK THEN!!!

:---[===] *

That's true. On the other hand, if the black hole had an outburst of some sort after swallowing that dust cloud 26,000 years ago, we will soon know about it!

Ann

[orin stepanek]

Poor little 'o nebula! Very interesting picture! though

[Doctor]

This is an illustration, not an actual picture. Please forgive me if you knew it was an illustration; but, the word used by two posters is "picture", as if it is an image taken by a telescope.

[moonstruck]

Well, I guess it's a picture of an illustration. It's mind boggling whatever it is.

[Chris Peterson]

You do realize that this has taken place already. We do not see things in real time.

But it doesn't matter. And the way that time and space are defined within relativity, what we are seeing is generally considered real time, regardless of distance. "Now" is a slippery concept in modern physics!

[HappyHappyJoyJoy]

What a cool picture! It bears a striking resemblance to an electron shell diagram. Maybe there's an ultra-super giant carbon atom at the heart of the galaxy!

[jando*]

After such monsters eat a meal, do they not belch radiation? One associates black holes with intense radiation - as already mentioned [- the Sagitarius A* radio source]

[Chris Peterson]

After such monsters eat a meal, do they not belch radiation? One associates black holes with intense radiation - as already mentioned [- the Sagitarius A* radio source]

What they are consuming belches radiation before it is eaten. A black hole itself produces no radiation (except, probably, for black body radiation).

[Charlie Patriot]

Once again I am totally confused ( no suprise) but looking at the orbits of the central stars makes no sense to me. If a massive gravitational field is present why aren't these stars in an elliptical orbit instead of random orbits.? Some are orbiting towards the field and then away from......?

[Ann]

You do realize that this has taken place already. We do not see things in real time.

But it doesn't matter. And the way that time and space are defined within relativity, what we are seeing is generally considered real time, regardless of distance. "Now" is a slippery concept in modern physics!

Well, that's why they call it "spacetime", isn't it? "Now" can only happen here.

Ann

[Chris Peterson]

Well, that's why they call it "spacetime", isn't it? "Now" can only happen here.

Which is what makes "now" so slippery, because that's pretty counter-intuitive to our everyday thinking about the concept.

[Chris Peterson]

Once again I am totally confused ( no suprise) but looking at the orbits of the central stars makes no sense to me. If a massive gravitational field is present why aren't these stars in an elliptical orbit instead of random orbits.? Some are orbiting towards the field and then away from......?

I'm not sure what you're seeing. The central stars, with their orbits shown in blue, are in elliptical orbits. Their inclinations are all over the place, but that is to be expected in the absence of any mechanism to pull them all onto a single orbital plane.

[nstahl]

Once again I am totally confused ( no suprise) but looking at the orbits of the central stars makes no sense to me. If a massive gravitational field is present why aren't these stars in an elliptical orbit instead of random orbits.? Some are orbiting towards the field and then away from......?

I dare say they are in elliptical orbits (as perturbed by various things around them and possibly relativistic effects due to all the gravity??). They are at random-looking orientations and sizes but the solar system has various-sized orbits. Our planets are in pretty much the same plane because at some point the dust and gas and chunks that became the planets had settled into that plane. But the stars around the center of the galaxy have arrived there from all directions (the galaxy is quite thick relative to the little region we're talking about) after interactions so diverse they would surely be considered random.

At least that's my take.

[Ann]

Isn't it true that the bulge of any spiral galaxy could be regarded as a miniature elliptical galaxy? Isn't the bulge of our own galaxy pretty similar to a small elliptical galaxy? And aren't elliptical galaxies elliptical because the stars in them haven't settled into a plane of rotation, but instead they swarm around like bees?

Come to think of it, isn't that what globular clusters are like, too?

Check out this APOD from 2002, which shows a simulation of the motions of the stars inside a star cluster.

Ann

[Chris Peterson]

Isn't it true that the bulge of any spiral galaxy could be regarded as a miniature elliptical galaxy? Isn't the bulge of our own galaxy pretty similar to a small elliptical galaxy? And aren't elliptical galaxies elliptical because the stars in them haven't settled into a plane of rotation, but instead they swarm around like bees?

Yes. And even in the disc, the stars are on different inclinations, just not so extreme as in the central bulge.

Come to think of it, isn't that what globular clusters are like, too?

Yes.

And anywhere else where some force other than gravity hasn't forced things into a plane. Because gravity can't do that.

[TNT]

I thought that elliptical galaxies were high-luminosity spiral galaxies, as shown in an APOD roughly 7-12 months ago (not sure how accurate that is). If I find it, I'll post a link to it.

[Chris Peterson]

I thought that elliptical galaxies were high-luminosity spiral galaxies, as shown in an APOD roughly 7-12 months ago (not sure how accurate that is). If I find it, I'll post a link to it.

There is clearly a continuum of galaxy types, which means there can be no perfectly clear border between different types- there are intermediates that are hard to classify. But certainly, most ellipticals are dynamically different from most spirals.

[nstahl]

And anywhere else where some force other than gravity hasn't forced things into a plane. Because gravity can't do that.

Exactly. Surely in the case of a planetary system the glob of gas and dust that will become the star and planets, etc. starts with some net rotational momentum about an axis through the center of mass, which would define the plane the system ends in. But to start with, there'd be lots of stuff out of that plane orbiting around the center of mass from all directions and colliding with other parts causing, I'd imagine, some losing enough momentum it falls to the center and some being diverted over time into the plane the system ends up occupying. A sort of friction.

For an elliptical galaxy, that hasn't happened; I suppose because the gas and dust condensed into stars and such before it could cause enough "friction" on a galaxy-wide scale to reduce it to a plane.

At least that's my intuition.

[Chris Peterson]

Exactly. Surely in the case of a planetary system the glob of gas and dust that will become the star and planets, etc. starts with some net rotational momentum about an axis through the center of mass, which would define the plane the system ends in. But to start with, there'd be lots of stuff out of that plane orbiting around the center of mass from all directions and colliding with other parts causing, I'd imagine, some losing enough momentum it falls to the center and some being diverted over time into the plane the system ends up occupying. A sort of friction.

For an elliptical galaxy, that hasn't happened; I suppose because the gas and dust condensed into stars and such before it could cause enough "friction" on a galaxy-wide scale to reduce it to a plane.

At least that's my intuition.

I think so, too. Stellar systems, and some galaxies, flatten because of fluid dynamic effects- momentum transfer due to particle collisions, electromagnetic interaction, and photon momentum. While the ordinary matter in galaxies is often orbiting in something approximating a plane (because of the above stated interactions), dark matter orbits in a spherical halo. In the absence of any interactions outside of gravity, there is nothing to move it onto a plane.

[Sam]

I appreciate that, for once, a huge exciting astronomical event is going to happen in a short time.
No waiting 1000 years to see the Betelgeuse supernova, or 5 billion for the Sun to expand to a red giant. Even the next solar eclipse I'll have a chance to see won't occur until 2017!

What kind of pictures can we expect to see? Will the action show up in radio and infrared?

--
Sam