A Recipe For Black Holes

hozzies writes: "This article at Space.com explains why black holes are "relatively nearby in cosmic terms... [but] don't seem to be eating much these days." This phenomenon has fascinated both scientists and the general public since it was first theorized. It explains a big chunk of the early universe—that is, if we can every prove they exist in the first place."

Comments

Phooey!

[jd]

And I thought this was going to be some kind of bake-your-own-Black-Hole article. Oh well!

One of the problems with many studies of Black Holes is that nobody really knows what to look for. Despite many attempts, nobody has actually detected the only definitive proof of a Black Hole, Hawking Radiation.

Many things in space emit X-Rays and Gamma Rays. Some are even "brighter" than Black Holes. There have even been a few events comparable in energy to the Big Bang itself. Also, the requirements for a Black Hole to form are somewhat extreme. You need to -start- with a star of greater mass than Chandrasaker Limit, which is about 3 solar masses. Following the death of the star, the gravitational attraction has to overwhelm everything else. ie: A star that gets ripped to shreds by a nearby massive object is unlikely to form a Black Hole.

Hawking Radiation is radiation which results from virtual particles on, or just outside, the Event Horizon splitting up. This causes the Black Hole to "radiate". This "radiation" will, in theory, eventually cause Black Holes to evaporate. (This is a requirement of Quantum Mechanics, which prohibits any point in space from having no entropy.)

Until this radiation is detected, most suspected Black Holes are just that - suspected, not determined. Now, there are a few objects that can reasonably be assumed to be Black Holes, simply because it is possible to show that there is a massive, dark object being orbited by a star that is being literally vaccuumed out of space. There isn't much room for doubt, in such cases.

But they seem to be finding Black Holes everywhere. If you count all the "missing mass", Black Holes, and other alleged particles, you'll probably end up with 900% of the mass of the Universe. Ummm.... sorry to break it to you astronomer guys, but 100% is the limit. :)

Re:Phooey!

[Kibo]

One of the problems with many studies of Black Holes is that nobody really knows what to look for. Despite many attempts, nobody has actually detected the only definitive proof of a Black Hole, Hawking Radiation.

Hawking Radiation is a very soft lowlevel buzz. If you had a black hole the size of a proton or so, it would make a tremendous explosion, but a black hold of any real size would make Hawking radiation all but undetectable. How ever if you have a totally dark object which occupies a small volume and has a mass of greater than 3 suns, you have a black hole.

Many things in space emit X-Rays and Gamma Rays. Some are even "brighter" than Black Holes.

Pardon me for stating the obvious, but almost everything in space is brighter than black holes, that's why they're called black holes. However, little is brighter than the accreation disks of super massive black holes, save the jets of plasma that they fling off. Many think that Quasars are ancient black holes in a period of youthful exhuberance tilted at a happy angle for our viewing enjoyment.

You need to -start- with a star of greater mass than Chandrasaker Limit, which is about 3 solar masses.

Umm the Chandrasekhar limit governs the formation of neutron stars and is 1.4 solar masses. And that is b the starting mass of the star, that is the required mass of the core left exposed by the supernova. Most stars will leave a white dwarf of glowing white and a beautiful nebula as testimate to their lives. But those who's core are greater than 1.4 solar masses degenerate into neutron stars instead. The mass of the core is so great that the electrons and protons are forced into a cohabitation, and can never break the lease. Thus a star only made of neutrons with a 1 km thick shell of iron for good measure.

Until this radiation is detected, most suspected Black Holes are just that - suspected, not determined.

You might be surprised to learn a great many cosmologists disagree with you. As does the esteemed Dr. Hawking. He bet a colleague a black hole (Cygnus X-1) was not really a black hole; the prize was a subscription to Penthouse. Hawking paid off, and that was in the 80's IIRC.

But they seem to be finding Black Holes everywhere. If you count all the "missing mass", Black Holes, and other alleged particles, you'll probably end up with 900% of the mass of the Universe. Ummm.... sorry to break it to you astronomer guys, but 100% is the limit. :)

The Universe is very very heavy. Finding many many more black holes, and kinds of black holes will not alter, in any meaningful way, the mass of the universe. We found something like 30% of the mass of the universe by discovering neutrinos have mass. They ain't much to look at, but you get enough of them together and they'll surprise you. Most current accountings of the universe have us as flat, which oddly enough it pretty well in agreement with what we observe.

I would recomend a book called Black Holes by Pierre Luminte IIRC, or Stellar Interiors: physical principles, structure and evolution.. The later has little on black holes, but you'll learn about all sorts of neat stuff. But its a little technical too, in case thats not your cup of tea.

sigh, sorry for the nit-picking

[Gaccm]

every [sic] prove they exist in the first place.

For something to be provable in science it must be testable everywhere. Black holes, _by definition_ devour all light [information] that crosses the event horizon, and anything outside the event horizon isn't part of a black hole. Black hole can never be "proved" in the traditional sense, but that doesn't stop people from accepting that the overwhelming amount of circumstancial evidense, none of the info proves black holes, but the only thing that could do all of the proof is black hole [the proofs i'm talking about, are the light curvature around them, x-ray jet streams, and other random stuff like that.

Re:sigh, sorry for the nit-picking

[SIGFPE]

I think you refute your own argument. If black holes "devour all light [information] that crosses the event horizon" (and that's certainly not a universally accepted definition - see the article in Scientific American, April 1997) then you can prove the existence of a black hole by finding a region of space which appears to devour all light. Trivial. Maybe I misunderstand you and you're making a deeper point. If so, please explain.
--

Welcom to Missouri

[Kibo]

Black holes are pretty well accepted to exist, in a multitude of flavors I might add. There is a wealth of evidence from many sources that pretty well prove it. If the author means proof in the sence of walking up to the edge and tossing a star in, well grow up. Abstraction isn't a four letter word. I can't see an atom with the naked eye either, but their existance is quite certain from infered information. Sure, this information is pretty direct. But Rutherford's inferance of nuclei at the center of atoms in a sheet of gold is about the level of proof we've got for black holes. What are they like at the singularity? Well that's the realm of science yet to be invented. I think there's a place for scepticism, but this isn't it. Couldn't time be better spent disproving moon landings? For love of god, Hawking already paid off that bet. Black Holes are real, because you can't return a subscription to Penthouse.

Black Holes Proof Here

[TechnoGrl]

Actually fairly recently both measurements of space-time dragging effectsas well as the accretion disk around several black holes. Plus the BH at the center of our galaxy has recently been pinpointed by observing several start orbiting around it waiting to be gobbled up. This pretty much makes them an observational reality

You can find the articles here:

http://web.mit.edu/newsoffice/nr/1997/blackholes .h tml

and here:

http://cfa-www.harvard.edu/blackhole/release.htm l

and here:

http://www.space.com/scienceastronomy/astronomy/ ou r_black_hole_000920.html