Black Holes: Integral part of a Galaxy?

[NaptownKnight]

What credibility would any of you guys give to the theory that in the center of each galaxy is a super massive black hole? I was reading a tiny bit, and wondered if it were possible that it could be true. also, why would this be important to a galaxy?

[QRS]

I always thought that the center of each galaxy was just a huge mass of stars.

Galaxies are an integral part of the universe, just not in that way.

[Ginko]

And if it would be a super black whole... thatb would suck everything up woudnt it?

[Georgy Zhukov]

From what I know the center of the galaxy is just a huge density of gas and dust and also where all new stars are created.

[Gelgoog]

What credibility would any of you guys give to the theory that in the center of each galaxy is a super massive black hole? I was reading a tiny bit, and wondered if it were possible that it could be true. also, why would this be important to a galaxy?

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Techniques for finding black holes




Most accretion disks and gas jets are not clear proof that a stellar-mass black hole is present, because other massive, ultra-dense objects such as neutron stars and white dwarfs cause accretion disks and gas jets to form and to behave in the same ways as those around black holes. But they can often help by telling astronomers where it might be worth looking for a black hole.

On the other hand, extremely large accretion disks and gas jets may be good evidence for the presence of supermassive black holes, because as far as we know any mass large enough to power these phenomena must be a black hole.

Gravitational lensing


A gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is "bent" around a massive object (such as a black hole) between the source object and the observer. The process is known as gravitational lensing, and is one of the predictions of Albert Einstein's general theory of relativity. According to this theory, mass "warps" space-time to create gravitational fields and therefore bend light as a result.

A source image behind the lens may appear as multiple images to the observer. In cases where the source, massive lensing object, and the observer lie in a straight line, the source will appear as a ring behind the massive object.

Gravitational lensing can be caused by objects other than black holes, because any very strong gravitational field will bend light rays. Some of these multiple-image effects are probably produced by distant galaxies.



Objects orbiting possible black holes


Some large celestial objects are almost certainly orbiting around black holes, and the principles behind this conclusion are surprisingly simple if we consider a circular orbit first (although all known closed astronomical orbits are elliptical):

* The radius of the central object round which the observed object is orbiting must be less than the radius of the orbit, otherwise the two objects would collide.
* The orbital period and the radius of the orbit make it easy to calculate the centrifugal force created by the orbiting object. Strictly speaking, the centrifugal force also depends on the orbiting object's mass, but the next two steps show why we can get away with pretending this is a fixed number: e.g., 1.
* The gravitational attraction between the central object and the orbiting object must be exactly equal to the centrifugal force, otherwise the orbiting body would either spiral into the central object or drift away.
* The required gravitational attraction depends on the mass of the central object, the mass of the orbiting object, and the radius of the orbit. But we can simplify the calculation of both the centrifugal force and the gravitational attraction by pretending that the mass of the orbiting object is the same fixed number: e.g., 1. This makes it very easy to calculate the mass of the central object.
* If the Schwarzschild radius for a body with the mass of the central object is greater than the maximum radius of the central object, the central object must be a black hole whose event horizon's radius is equal to the Schwarzschild radius.
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heres the info you'd be looking for.

Supermassive black holes at the centers of galaxies



According to the American Astronomical Society, every large galaxy has a supermassive black hole at its center. The black hole’s mass is proportional to the mass of the host galaxy, suggesting that the two are linked very closely. The Hubble and ground-based telescopes in Hawaii were used in a large survey of galaxies.

For decades, astronomers have used the term "active galaxy" to describe galaxies with unusual characteristics, such as unusual spectral line emission and very strong radio emission.[30][31] However, theoretical and observational studies have shown that the active galactic nuclei (AGN) in these galaxies may contain supermassive black holes.[30][31] The models of these AGN consist of a central black hole that may be millions or billions of times more massive than the Sun; a disk of gas and dust called an accretion disk; and two jets that are perpendicular to the accretion disk.[31]

Although supermassive black holes are expected to be found in most AGN, only some galaxies' nuclei have been more carefully studied in attempts to both identify and measure the actual masses of the central supermassive black hole candidates. Some of the most notable galaxies with supermassive black hole candidates include the Andromeda Galaxy, M32, M87, NGC 3115, NGC 3377, NGC 4258, and the Sombrero Galaxy.[32]

Astronomers are confident that our own Milky Way galaxy has a supermassive black hole at its center, in a region called Sagittarius A*: