Question on Super Massive Black Holes?

Question

I watched a tv program last night on super massive black holes and i am fascinated in stuff like that, but you'll have to forgive my lamens terms when im asking the question here. Okay so they know that the black hole is there at the center of the andromeda galaxy because of how fast stars are moving around the center and that made sense, but what i am wondering is if we can't actually see the black hole then how do we know that its there? The show did this illustration where it shows how black holes literally bend space time to the breaking point and no one is sure what is going on inside the black hole or the singularity? I guess basically what im asking is why does it have to be a black hole and not just a super massive central sun? I mean if all we can see is bright light around the center why the black hole? does that make sense? Also on this program they said that we believe there is an upwards of 120 billion galaxies in the universe? thats unbelievable!

Answer 1

>Okay so they know that the black hole is there at the center of the andromeda galaxy because of how fast stars are moving around the center and that made sense, but what i am wondering is if we can't actually see the black hole then how do we know that its there?

The idea that black holes are black and can't be seen by light is not always the case. Many black holes are in the process of consuming large amounts of interstellar gas, and as the gas falls into the black hole, it is heated to the point where it emits a lot of light before it passes the event horizon, causing black holes that are doing this to glow quite brightly (especially in the x-ray frequencies, and mostly along the axes of rotation). That said, that is NOT the way we can detect supermassive black holes at the centers of galaxies. Instead, we just use the gravitational effects on nearby objects. When you see stars accelerating so quickly around what looks like nothing at all, you know there has to be some massive but relatively dim gravitational body there, and only black holes fit the observed characteristics of the object.

>I guess basically what im asking is why does it have to be a black hole and not just a super massive central sun?

A large star would glow brightly and be easily visible against the stars around it. Black holes would not tend to glow so brightly, and most of the glow would be along the narrow axes of rotation. Additionally, stars have an upper limit on how massive they can be, and their lifetimes decrease quickly as you get more massive; the Sun has a lifetime of about ten billion years, but stars only 20 times as massive as the Sun only last perhaps a hundred million years or less before exploding. Black holes can have millions of times the mass of the Sun, so much that no star would really exist for very long as a star under those conditions; it would almost immediately explode and have its core become a black hole anyway.

>Also on this program they said that we believe there is an upwards of 120 billion galaxies in the universe? thats unbelievable!

The standard figure is actually about 70 trillion galaxies in the Universe. Your figure is over 500 times too small.

Answer 2

The question is not, whether something makes sense or not. How we can know a black hole is there ? Well, you answered it yourself, by the kiond of movements of other objects around it. ... and also by watching the black hole indirectly . Due to its great power of gravity, we could see some stars twice that are positioned right behind the black hole that's called a "lense effect" there are other effects, too, that show us indirectly here is a black hole. The so called braight light is only the kind of energy that is visible to the eye ... but with black holes, there are also some typical emmisions of x-ray and gamma, so called jets ... we can detect by using appropriate instruments, so we do know fore sure at a determined spot, whether there is a so called black hole or not. Super massive central suns ... central or not, will collapse as ome point, too (at the end of their "lives" as a sun, and then will become either a neutron star, or a brown dwarf, or, if been massive enough before evolve into a so called black hole.

120 billion galaxies? No, this is not inbelievable ... it just appears as if you cannot imagine such a number. But its so simple. You can easily calculate it. it's simple math. Just count all galaxies on the so callee deep field image of the hubble telescope, and know that this image show only a tiny part of the universe, I don't know how much, but I guess it's less than one arc second. Multiply what you have counted with 3600, and you'll have jsut a small stripe of the universe all around you, now take the result and multiply that once more with 1800 to get into all directions and you'll have the estimate number of galaxies.

Answer 3

Check it out...I have the answer for you.
I'll try to and explain this a little bit to why scientist believe the center of our galaxy to be a supermassive blackhole. For one, if our center of our galaxy was just a super-super massive star it would fuse all of its fuel in a matter of a few thousand years and would be extremely unstable. The star would die in a spectacular supernova and much of the galaxy would be blown away out in to the universe. And if we looked out in to the universe at other galaxies we would see a lot more of this going on. Two, if it were a star it's luminosity would be much much brighter than it is. Scientist also know that it can't be only a tightly packed group of stars because the luminosity of the entire galaxy center stays consistent when the overall luminosity changes. This is especially convincing because this would be impossible with a group of tightly packed stars because light doesn't travel fast enough from one side of a galaxy center to the other for the luminosity to stay consistent all the way through. But if the object changing the luminosity of a galaxies core was a massive object like a supermassive black hole then this would explain why the luminosity rises and falls consistently throughout the entire galaxies center. I hope this helps answer your question.

Also just to add on to what I said:
The object in the center of our galaxy would have to contain a lot more mass than a regular star, on the basis of how large it is, to have the gravitational influence on the rest of the galaxy that it does. Also, black holes release powerful x-rays due to extremely high temperatures, that we have also discovered at the center of our galaxy.

Answer 4

Because a sun that powerful would also be very bright. And huge. Remember - a black hole, any black hole, is just a dimensionless point in space. It's the size of the Event Horizon that tells us how massive it is - well, that, and the effects it has on nearby stars.

For a star to be that massive, it would have to be huge. The only explanation for that much mass in such a small space is a black hole.

Answer 5

We know black holes exist based on their interactions with matter we can see.
Black holes are extremely dense, no star could get that dense. For a star to be as dense as a black hole it would have to shrink down to the Schawrzchild Radius, which would be the radius that if the star's mass was confined to it, its gravitational pull would be so strong nothing would escape it. For example, the sun's Schwarzchild Radius is 3 kilometers! But the sun is much much larger than that. So what I'm trying to say is that it couldn't possibly be a huge star at the center of galaxies, otherwise its size would be so big it would probably a considerable size of the galaxy, no such stars exist, and if they did we would see them.

Answer 6

you have multiple questions but I will focus on the one about the black holes. We infer that they are there based upon the actions of surrounding material. Everything we know about motion and energy says that matter won't just swirl for no reason; it has to be attracted by something. Since there are times we can't see what that something is we conclude it is a black hole. Lastly, wrap your mind around this there are about 1*10^22 stars in the universe. That like the number of galaxies times a trillion.

Answer 7

It has to do with the escape velocity of the black hole. The Escape velocity of the Earth is 25,000 mile per hour. That is how fast you need to go to escape the gravitational pull of the Earth, any slower and you'lll just be locked in an orbit around the Earth or if less than 18,000 miles an hour you'l fall back to Earth. The more massive the body the greater the escape velocity. A black hole's mass is so great that its escape velocity is actually higher than the speed of light, 186,000 miles per second. Anything that gets within the diameter of that escape velocity disappears over the event horizon of that 186,000 mile per hour escape velocity and cannot be seen. That is why it is black, and why it is called a hole, everything that goes in doesn't come out.

Answer 8

All the Galaxy's have a black hole in the center so that all solar systems are in orbit around the center. This way solar systems can orbit for centuries. The gravity well that is produced by the black hole can be 100 light years across.

Answer 9

the enormous deal is definitely area: as those 2 products get closer at the same time, the part of each and every black hollow living in the authentic universe is occupying area this is getting nearer. To be clean, the black holes are autonomous at this element, however the gap between them is changing. as the two black holes attain close proximity, the blended bending of area warps the gap between like a mattress sheet being shaken in the wind. area won't be able to tolerate 2 black holes in a similar section that are of distinctive frequencies and harmonics, so area definitely performs paintings on each and every of the two bodies till while they collide, their actual properties tournament one yet another very precisely. for this reason, they integrate thoroughly and alter right into a greater rendition of a mixture of the two autonomous bodies. element is, while they collide, no paintings is accomplished on the factor of their frontier this is in the authentic universe.

Answer 10

The extreme gravity produced by a black hole will bend light creating a sort of lense effect. If a star passed behind a black hole its speed would appear to us to change dramatically. Imagine moving a magnifying glass over a newspaper and seeing how the letters move and warp as you pass over them.