Second Black Hole at the Center of the Milky Way

Tsalg pastes "A second black hole lurks at the centre of our Galaxy, according to astronomers who have watched a cluster of stars spinning around it. Just three years ago, astronomers confirmed that the Milky Way revolves around a supermassive black hole, called Sagittarius A*, which is about 2.6 million times more massive than the Sun. But now a much smaller black hole, just 1,300 times our Sun's mass, has been found orbiting about three light years away from its supermassive cousin. placing it intermediate between the relatively small (stellar mass) black holes in the Milky way Galaxy and the supermassive black holes found in the nuclei of galaxies."

Comments

Contradictory?

[dshaw858]

I thought that the goin theory was that at the center of each galaxy lay a black hole, which created the "spiral" effect (such as the one that we see in the Milky Way's "arms"). Does this contradict current knowledge, or is our galaxy just a fluke?

- dshaw

Re:Contradictory?

[anubi]

One thing that has been puzzling the hell out of me...

If the "big bang" theory is correct, and the entire universe emanated from a point -

Where did all this rotational inertia come from???

I guess the primordial point we supposedly came from was spinning?

Is it likely that "black holes" can be spun up so much from ingesting incoming rotational inertia that they become unstable and sling themselves apart... aka, the "big bang"?

I am not a cosmologist, or even a cosmetician as far as that goes, but I often ponder on why everything I see seems to be spinning.

black hole collision

[i_should_be_working]

any astronomers know what to expect to see when two black holes collide? we have pictures of stars colliding or ripping each other apart. we have ones of whole galaxies colliding. but what about black holes?

Re:black hole collision

[Carnildo]

If black hole "A" combines with black hole "B", the resulting black hole will have a greater mass, and thus a larger event horizon.

Re:black hole collision

[chenzhen]

Actually this is a pretty tough problem to solve. The computation was attempted by several leading numerical relativity institutions some years ago, but met with no success. The professor I work for is currently building up a code that will hopefully someday be able to handle the binary collision problem.

One of the major problems is that programs crash pretty quickly when the evolution develops a singularity. A good method for avoiding this is called excision, where the singularity is removed from the grid and replaced with boundary conditions. This was recently implemented in my advisor's group and applied to the binary neutron star problem. At the end of the evolution, a black hole forms, so it doesn't seem like there are too many steps before a full black hole collision is possible.

Re:black hole collision

[chenzhen]

On second thought I shouldn't say no success. There have been successes in computing special, less physical cases, for example in treating the stars as frictionless dustballs not possessing magnetic fields. But these features are very important in determining the rotation structure of stellar fluids, and are probably essential in modeling the physically correct binary merger. The general problem remains to be solved, and the goal is to figure out what physical processes produce gravitational waves, so that we know what to be looking for experimentally.

Here are some visualizations of previous merger simulations:
1
2

What are the odds

[Anonymous Coward]

that my immediate guess, that it's the remains from a swallowed dwarf galaxy, is correct?

Scary

[Anonymous Coward]

I'm not sure why, but the concept of Black holes lurking out in the cosmos is scary!
I've allways had a fear that, despite out best efforts as intelegent beings, the universe as a whole will be fated to a cold, dark future, without any intelegent life and one big black hole. Or (almost as bad) a repetition of itself.

I think there is a phobia for that, it was on star treck once, nelix had it.

I dunno if HUMANS have the average intelegence to escape earh before extinction, but I hope some race will save the few decent humans.

Re:Scary

[FooAtWFU]

A few words of reassurance.
Remember, a black hole doesn't have any magical sucking power. It's just gravity. If a star collapsed into a black hole, its gravitational pull doesn't get any stronger. It's still the same mass, it's just a lot denser. Contrary to what science fiction shows will tell you, it won't start "sucking in" anything that the star it collapsed from wasn't already "sucking in".

Now consider how often you see planets and stars collide. You ever hear about it? Even when two galaxies run into each other, they tend to just fly apart into a rather incoherent mess instead of individual stars going anywhere- due to gravity, orbital mechanics, density, all that.

Remember: space is very, very, very, unimaginably big. I believe in the book Einstein's Universe (excellent explanation of relativity, including some stuff on black holes, for the nonexperts) they discussed the density of matter which would be required if the universe were to reach a steady state, not expanding or contracting, and they came up with a ballpark figure of about a baseball-size mass every cubic light year (pun optional), and went on to say that current observations of the universe indicated that this seems to be much more than actually exists.