What Is At The Centre Of A Galaxy?

[naomi24]

A question arising in my home from the BBC programme ‘Stargazing Live’ tonight. Moons revolve around planets, planets revolve around suns, and the whole lot revolves around …. what?

[douglas9401]

My wife. :P

[DaisyNonna]

Chocolate

[Frank97]

A black hole?
http://en.wikipedia.org/wiki/Galactic_Center

[Zacs-Master]

Hey, this isn't Chatterbank you know. Anyway, the related threads function. Has kicked in although there might be more recent developments than those known in 2006.

[Mojo-Jo-Jo]

It's thought that a black hole lies at the centre of each galaxy, including ours.
Contrary to popular belief, a black hole does not just keep growing and sucking everything up. It has a limit, called the Schwarszchild Radius, at which point its gravitational pull is not powerful enough to pull the rotating mass around it in.

[Arksided]

My understanding was a supermassive black hole, which do produce outbursts:
http://www.huffingtonpost.co.uk/2012/10/24/massive-flare-erupts-black-hole-milky-way_n_2007960.html

[JonnyBoy12]

A supermassive black hole. In the case of our own galaxy it is thought to have a mass of about 13.5 million of our suns.

[Old_Geezer]

Now what's the universe revolving around ;-)

[naomi24]

Now I'm confused. Beso, I don't know what you mean.

Mohsen, what's that? An advert?

[Old_Geezer]

Maybe my ignorance too but I suspect beso's answer is in a similar vein to wildwood's. Not to be taken too seriously ;-)

[naomi24]

OG, me too - but I'm confused enough without jokers! ;o)

[Teddio]

Binary star systems are common in our galaxy. Two stars orbit around nothing ! (called the common centre of gravity)
However the orbital dynamics of galaxies, especially our own, suggest there is a massive black hole at the centre.

[mibn2cweus]

Objects in motion tend to continue to move at a constant velocity in a straight line. We call this tendency, inertia. Meanwhile, gravity, in proportion to mass and distance, tends to cause objects to accelerate towards one another. in effect, 'pulling' objects together. At some point a balance between these two opposing forces is achieved, thereby establishing an orbit, which is essentially two or more bodies falling around each other. The more massive object will tend to remain in its place, possessing the larger share of both inertia and gravity, causing the less massive (and typically smaller) object to orbit around it. As a result of this relationship between mass, inertia and gravity, super massive black holes, which are victims of their own losing battle with gravity, form and take centre stage within a galaxy.

[pdq1]

Yes I get a bit confused. To explain the idea of an exploding universe they come up with a balloon and put dots around it and put air into it. This is supposed to show galaxies getting further and further apart. However nothing is explained about the void within the balloon. Maybe this is the black hole we keep hearing about?

[naomi24]

I think you're supposed to imagine there are dots inside the balloon too - also expanding outwards as the balloon expands outwards.

[Nibble]

According to wiki & NASA, then, as far as science can discover with the current measuringdevices available then....

The complex astronomical radio source Sagittarius A appears to be located almost exactly at the Galactic Center (approx. 18 hrs, -29 deg), and contains an intense compact radio source, Sagittarius A*, which coincides with a supermassive black hole at the center of our Galaxy. Accretion of gas onto the black hole, probably involving a disk around it, would release energy to power the radio source, itself much larger than the black hole. The latter is too small to see with present instruments.