Do we know whats at the center of galaxies yet?

[Topher925]

Probably a stupid question as I'm sure we don't but stargazing gets me thinking. The last prevailing theory that I heard of was a massive black hole at the center of the milky way (and all other galaxies). However, the core of the galaxy is the brightest part by far and other than extremely large amounts of gravity, it doesn't appear to have any other characteristics of a black hole (as far as I know anyway). Are there any other creditable theories out there?

 

[DaveC426913]

...it doesn't appear to have any other characteristics of a black hole...

Such as?

We're pretty sure it's a SMBH. It has a lower constraint on its mass, based on objects in orbit around it. It also has an upper constraint on its size - also based on objects in orbit around it. The only object we know of with that mass and that radius is a black hole.

Here's a cool animation showing the orbits of some of the stars in VERY close orbit.
http://chargedmagazine.org/2012/05/supermassive-black-hole-causing-a-stir-in-the-milky-way/
SO-16 virtually grazes it, defining at least one upper limit on its size.

Based on orbits like these, calculations show the object can't be larger than our solar system, in fact, not larger than Jupiter's orbit I think.

There's a thread here on PF somewhere that goes into more detail.
As for brightness, our SMBH is closely surrounded by a very dense group of many, many millions of stars. That's why the core as a whole is so bright.

 

[Drakkith]

However, the core of the galaxy is the brightest part by far and other than extremely large amounts of gravity, it doesn't appear to have any other characteristics of a black hole (as far as I know anyway). Are there any other creditable theories out there?

Read this article: http://en.wikipedia.org/wiki/Supermassive_black_hole

 

[twofish-quant]

However, the core of the galaxy is the brightest part by far and other than extremely large amounts of gravity, it doesn't appear to have any other characteristics of a black hole (as far as I know anyway).

I think there is confusion about what is mean by "core". There is indeed a cluster of stars about 1000 light years across, but at the center of that, there is this mysterious dark object and we can tell what it's doing by seeing the nearby stars orbits around it.

 

[pmacias]

Thank you for your question. I can say that the center of galaxies is a topic of ongoing research and there is no definitive answer yet. The most widely accepted theory is indeed the presence of a massive black hole at the center of galaxies, including our own Milky Way. This is supported by various observations, such as the high velocities of stars near the center of galaxies and the emission of powerful jets of energy from the center.

However, there are also other credible theories that have been proposed. For example, some scientists have suggested that there could be a dense cluster of stars or a large concentration of dark matter at the center of galaxies. These theories are still being studied and debated, and more evidence is needed to support them.

It is important to keep in mind that the center of galaxies is a highly complex and dynamic environment, and our understanding of it is constantly evolving as we gather more data and refine our theories. So while we may not have a definitive answer yet, ongoing research and observations are helping us to better understand what lies at the center of galaxies. Thank you for your interest in this fascinating topic.