Black holes are the powerhouse of galaxies. They are typically millions of times more massive than the Sun, yet occupy no space at all (this is a topic for an entire other post). Black holes exert a tremendously large gravitational pull, since gravity is the strongest for massive, small objects. One common misconception about black holes is that they suck material in. This just isn’t the case. If the Sun were replaced with a black hole with the same mass, the Earth would happily orbit this black hole without being pulled in (of course, the lack of sunlight would be bad for all life on Earth). For the most massive black holes, found in the center of many galaxies, there is nearby gas and dust that orbits the black hole at very close distances. This structure is known as an “accretion disk”, since the matter within the disk eventually falls into the black hole.
In a paper titled, “Ionization structure and Fe K alpha energy for irradiated accretion disks”, X. L. Zhou, Y. H. Zhao and R. Soria explore the structure of these accretion disks. Astronomers can trace the amount of energy in a system by examining the spectrum of an object. If there are a lot of high energy photons zipping around, many elements will exhibit ionized states. The more energy, the higher amount of ionization. At very high energies, such as those found in the X-ray portion of the spectrum, only the elements with a large amount of electrons are still able to be ionized. One of these elements is Iron, which is found all over the Universe, from distant galaxies, to the Sun, to your red blood cells. Zhou and the rest of the authors calculated the amount of ionization you would expect for black holes of a certain mass and distance above the accretion disk midplane. By comparing their predictions to observations, they can infer the mass of the black hole and configuration of the accretion disk.
These type of studies can help astronomers study the interactions between black holes and disks, and how they impact the formation and evolution of galaxies just like our own Milky Way.
I don’t understand how a black hole can be both more massive and take up less space than the sun. For realz. Explamation, prease.
damn it, bochanski beat me to the lead / styrofoam dichotomy
what’s the difference between being sucked in and falling in? you say it doesn’t suck in, but that things eventually fall in.
are you saying some accretion disks are configured to suck, and others merely open to things falling in?
@Sully: You can have a brick made of lead and a brick made of styrofoam. Same size, different mass. Not exactly what’s going on with black holes, but the example works to a point.
@jonofthewoods: Material in the disk is being jostled around, and gradually material moves inward towards the black hole (where it is accreted). The only time things are “sucked” is after they pass a black hole’s “event horizon”, where even if they were moving close to the speed of light, they couldn’t escape the BH’s gravitational pull.
word. so what does the amount of energy in the system say about a disk? do we know how much energy is in our disk?
i can play this: energy in our disk ~ jupiter. the rest is rounding error. including us.
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