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Survey of Super Massive Black Holes Completed
eldavojohn writes "NASA has announced the completion of a survey of nearby supermassive black holes. Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged. From the article: 'Called active galactic nuclei, or AGN, these black holes have masses of up to billions of Suns compressed into a region about the size of our solar system. The all-sky census, performed using NASA's Swift satellite over a nine-month period, detected more than 200 nearby AGN.' I'm starting to feel very lucky to have grown up in the Milky Way Galaxy."
I can't be the only one that thought of the british band, "Muse" =D
Almost every major galaxy including the Milky Way has been found to have a supermassive black hole at its core. The only lucky part is our sun not being near to the core of the galaxy, not which galaxy it is in.
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The article says that it is every super massive black hole within 400 million light years. Also, as for being "lucky" to be in the Milky Way, our Galaxy has a super massive black hole at the center of it. Actually, we are a very typical galaxy. We are slightly larger than the average and we are a spiral galaxy (there are more elliptical galaxies and irregular galaxies than spiral). We are very typical. Also, as for being lucky about not being closer to the center of the galaxy (someone above mentioned that as well) if we were closer to the black hole at the center, it would not mean much. We are in an orbit around it and thus we won't be falling into it any time soon, even if we were closer to it. We do, though, have a great location in the galaxy. We are far enough out that we can look across the plane of our galaxy (only at some wavelengths because dust obscures a lot) and get a good view of it. We also can look out pretty well too. And to make things even cooler, our solar system actually bobs up and down through the main plane of the galaxy. It take about 30 million years to complete a complete cycle, but in 5 or so million years we will have a pretty cool view from above of the Milky Way. I don't remember exactly what the angle is that we would be viewing the galaxy from, not huge, but enough to be useful. The point of all this is that the advantage of this survey is to have a complete list of super massive black holes so as we are testing out theories we can apply these theories (and how they measure up) across not only a wide data set, but also a very complete set. There is so much left to be learned about black holes and this catalogue will certainly help.
First, the diameter of a "black hole" is proportional to its mass. The sun, for example, must be compressed to a diameter of about 3km to become a black hole. A black hole with the mass of billion suns would have a dameter=3 billion km or 1000 times our solar system. The density of this black hole would be "low" as in much thinner than air. (Do the math yourself. Mass of sun is 2x10E30kg)
Anyway, as a region of space gets denser, time slows down, and as the density approaches the density required to become black hole, time just freezes.
What you will see when looking at a "black hole" is just a region of space with the eventual event horizon of the hole just frozen in time, and as you move outside, time goes through the "molasses" stage, and as you get further away, gets normal.
The black hole will not form in any finite time since time there just stopped!
For the observer falling towards the "hole", time in the rest of the universe just speeds up. In a matter of minutes the universe will age billions of years, and the observer will first hand know the ultimate fate of the universe in a distant future.
don't cut it off www.mgmbill.org
Exactly.. here is a nice video to put the whole thing in perspective.
http://www.youtube.com/watch?v=mcBV-cXVWFw
I guess it sucks for you then.
Because there's a supermassive black hole at the center of our galaxy.
http://en.wikipedia.org/wiki/Sagittarius_A*
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So, you've seen this thing in the middle? What's it look like? Enquiring minds want to know!
You are possibly a troll, but it's rather standard to define the size of a black hole by the size of its event horizon. This is largely because we can't actually know anything about what there is behind the event horizon. Maybe there's a singularity there, and maybe there isn't. What we know of physics says there ought to be, but it seems impossible to observe, and trusting our physical theories in such extreme conditions is a big step of faith.
So, yes, in all the various articles about black holes that I've read, their size is defined by the size of their event horizon.
There are theories that posit the Universe is actually two-dimensional and that our experience of it as three-dimensional is actually more like a holographic projection of the two-dimensional reality. These theories are based on the relationship between a black hole's mass and its size that suggest that all the mass of a black hole is actually on the surface of the event horizon.
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So if it's 250 billion light years across, than the 'ends' would be 125 billion light years from the center. If the universe is only 14 billion years old, how did galaxies get 125 billion light years from the center at that time? They would have to travel at 10x the speed of light, and that's supposed to be impossible...