Black Hole at Center of Milky Way

kwertii writes: "The Washington Post reports new evidence that there is a black hole with the mass of 2.6 million suns at the center of our galaxy. The Chandra X-Ray Observatory happened to be looking at the presumed site of the hole at the moment it absorbed a comet, blasting x-rays off into space as a byproduct. The implication is that the Milky Way is slowly spiraling down into a giant galactic drain..."

No fear, the galaxy's safe.

[Jodrell]

A mass of 3 million Suns may seem a lot, but it isn't when you remember that the Galaxy is quite a bit bigger than that. It's unlikely that this Black Hole could "swallow" the galaxy, in fact it's probably the only reason our galaxy exists.

Incidentally, the BBC article is here [bbc.co.uk].

Shouln't this exact moment not last for ever??

[Deag]

I'm probably completely wrong here, but as you go near a black hole doesn't time not slow down, so to us this comet going into hole should last forever... or something???

Re:..Its not really suprising..

[tolan's my name]

They may have been, however a large [diameter] black-hole [and by that I just mean large diameter of event horizon] does not have to be very dense.

Basically if we take an object [well a sphere] of density d with a mass m then as we increase the diameter x [in a linear manner] the volume increases as x^3. So since g~m/x^2 the effective gravity on the perimeter increaes linearly.

In otherwords [in newtonian terms anyway] a large enougth object of any density would become a blackhole.

Interestingly as such an object would not necessarily be particuarly different from our world [ie if our universe is big enough and is evenly distributed etc then light is bounded, bounded universe ~ black-hole]

Re:Not necessarily spiralling into it

[JetJaguar]

You've got the first bit right, it's generally accepted that the difference between quasars, active galactic nuclei (less powerful quasars), and "normal" galaxies has to do with the amount of material falling into the galactic core, in quiet galaxies all the available material near the supermassive black hole has been sucked in and there's nothing left to cause a ruckus, whereas in quasars and AGN there's still stuff falling in.

As for Andromeda colliding with the Milky Way... Sigh. This is only hypothetical at best. Andromeda does have a negative radial velocity, but we do not know what the tangential velocity is. Before we can say, definitively, that Andromeda will collide with us, we MUST know the tangential velocity...we do not know what it is, and there isn't any easy way to measure it.

Anyone modeling Milky Way-Andromeda collisions are just satisfying their own intellectual curiosity. There's nothing wrong with that and I fully support it, but it's disengenuous to say that these models predict with any accuracy what will happen in the future.