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Post by Belle Diamante on Jun 10, 2002 17:07:15 GMT -5
Hey! for anyone who's still here. Do you think a enlarging black hole will engulf the universe? Is it possible? I saw a clip from a documentary about how the universe will eventually end. One theory is the black hole.
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Post by Toxic-Avenger on Jun 11, 2002 11:13:05 GMT -5
No, your Omega Theory bit once, is a more plausable answer.
It would have to a HUGE black hole, or several black holes. The answer for me is no, for several reasons.
Even if the 2.3 million solar mass black hole at the center of our galaxy started feeding on everything in the Milky Way, it would only become a trillion solar-mass black hole (or however many stars are in our galaxy) a few tens of thousands of light-years across. The accretion disk would be about the size of the now gone, Milky Way. The gravity and mass wouldn't be any more than the the galaxy the black hole replaced. <br> Then what? The Magellanic Clouds--mini-galaxies about 100,000 light-years away, would be unaffected by the new big black hole. The neighboring galaxies, NGC-205 and NGC-110 and their big brother, Andromeda, would still be unaffected. So the black hole that started in our galaxy would just sit there and take in all the matter left form the Milky Way until it used it all up. Then the black hole would just sit there. No one would know it was there except for some gravity lensing around it. <br> Now some galaxies are racing toward each other, like ours and Andromeda, at somewhere near half the speed of light. Other galaxies are speeding away from us, so a universe devouring black hole would never catch up to them. <br> ********************************************
I just read an article in Discover magazine that black holes are even weirder and more powerful than we thought. They don't just pull light in so it can't escape, but they actually grab on to space and time and drag them in. Spinning black holes act like hugeamongous electric generators with strong magnetic fields radiating out and surrounding the Event Horizon.
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Post by busybodies on Jul 3, 2002 9:54:04 GMT -5
I have a question. According to the Law of conservation of mass, if matter can neither be created nor destroyed, when a star collapses in on itself where does all the matter go? It can't be lost, can it?
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Post by Toxic-Avenger on Jul 3, 2002 10:51:47 GMT -5
/\ No, what happens is all the matter in a large star is compressed.
Some stars explode when they die, that's called a supernova. Other stars, like our sun, will expand into a red giant. In other words, it will be the size of Venus's orbit around the sun. Other stars, collapse and become black holes. Here's why.
Take a ten-solar mass sun, or a star that's as heavy as ten of our suns. The gasses and matter that make up this sun are very heavy, many hundreds of tons per square centimeter. When this star uses up all its fuel, it can't support its own weight anymore and it implodes at some 42,000 miles per second. The matter from the star hasn't gone anywhere, it's just the atoms and molecules have been compacted into a smaller area. The black hole is smaller, but it still has the weight of when it used to be a star. If it gets close to anything, it will pull it in and that will be added to its weight.
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Post by Cassiopeia on Jul 3, 2002 14:50:00 GMT -5
^^^ Yeah, but the mass would be the same. And gravity is directly proportional to mass, so wouldn't the gravity be the same. Sorry if I sound stupid; I just don't know too much about astronomy. Also, what does it mean exactly for a star to "die"? I know that it stops creating energy, but what physically happens to it?
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Post by busybodies on Jul 4, 2002 7:25:30 GMT -5
^^ A star dies when all the Hydrogen in it's core is finished and no more nuclear reactions can take place.
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Post by Cassiopeia on Jul 5, 2002 0:43:11 GMT -5
^^^ Thanks. That makes a lot of sense. I don't know why I didn't think about that on my own, because I do understand the basics of fusion.
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Post by Toxic-Avenger on Jul 5, 2002 10:41:08 GMT -5
Fusion is when two atoms are joined together to make a heavier element. To do this, you need tremendous heat and pressure, something a star can give both of. The fusion releases huge amounts of energy and the process is self-sustaining for millions upon million of years.
<< but the mass would be the same. And gravity is directly proportional to mass, so wouldn't the gravity be the same.>>
Definition: Solar mass, equal to the weight of our sun.
Yes. When a star, lets say twice the physical size of our sun collapses into a black hole, it takes up less space, but has the same weight, so its going to have the same gravity. This means the star, weighing in at about 600,000 solar masses is over one million 600,000 miles wide. Now it's a black hole with the same gravity, about 15,000,000 times that of Earth's, but now it's half the size of our sun, but it still weighs as much as much as over half-a-million of our suns.
Make sense? I'll clear it up.
<<I just don't know too much about astronomy. >>
Happy to help, It's a hobby.
<<what does it mean exactly for a star to "die"? I know that it stops creating energy, but what physically happens to it? >>
Lankan Lass pegged it, but as you can tell, I'm lovin' this so:
Depends on the star. Some stars use up all their energy and go out like a candle. The become a red dwarf star about the size of the Earth. Now it's just an ember that smolders for a million years.
Another star, say a solar system-sized blue super giant uses up all it's fuel in about ten million years. The star is a great candidate to becoming a black hole. The pressures in the star's core are tremendous as you can tell. Now this star collapses and becomes a black hole.
A star half this size can become a black hole, or it can blow itself apart in a supernova. This creates a huge cloud that over millions of years, becomes a nursury for new stars. The Veil, Crab, and 1997-A were supernovas.
Other stars can use up all its fuel, blow off its outer layers and create things like the Ring Nebula.
Others collapse not as violently as a black hole, and these become pulsars. The gravity is huge, but not like a black hole.
Others stars just burn up and fade away. From hot star to white dwarf, again the size of the Earth.
Our sun will start to use up it's fuel, then turn orange, and swell to the size of Venus' orbit around the sun. Needless to say, Venus will be gone when this happens and Earth's oceans will boil away. The the sun will swell to a red-giant, it's outer atmospher touching earth's, then it will shrink way down into a white dwarf and the earth will be a frozen peice of slag.
That's just a quicky on how stars die, there's many exceptions and variations.
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Post by Cassiopeia on Jul 5, 2002 23:16:34 GMT -5
>>Yes. When a star, lets say twice the physical size of our sun collapses into a black hole, it takes up less space, but has the same weight, so its going to have the same gravity. This means the star, weighing in at about 600,000 solar masses is over one million 600,000 miles wide. Now it's a black hole with the same gravity, about 15,000,000 times that of Earth's, but now it's half the size of our sun, but it still weighs as much as much as over half-a-million of our suns. <<
I still don't understand why a black whole has so much more energy and power than the star it evolved from. It still has the same gravity and mass; the only thing that changes is it's size, and therefore it becomes much denser. But how does density affect force?
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Post by Toxic-Avenger on Jul 8, 2002 12:50:55 GMT -5
Good questions!
<<why a black whole has so much more energy and power than the star it evolved from. It still has the same gravity and mass; the only thing that changes is it's size, and therefore it becomes much denser. But how does density affect force? >>
And the density is what makes the black hole have such a strong gravity. I should have mentioned this before, but the Singularity of a black hole, the point where the gravity is the strongest, the gravity is infinite. That's where the power comes from.
What's happening is, the gravity in this area is pulling everything in, including time and space. The power and energy being thrown off comes from the hub of the black hole, or the Event Horizon, the point of no return. The gasses, matter and everything else is rubbing against each other and being charged up so that the center of the black hole's accretion disk, sort of like a whirlpool, is heated to millions of degrees. This blows off huge jets of x-rays.
So if a black hole is so strong, why doesn't it pull everything in? Because the gravity, though strong, falls off rapidly outside the accretion disk.
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Post by Toxic-Avenger on Jul 17, 2002 12:53:31 GMT -5
Here's some new facts I found. Enjoy.
'Death Spiral' Around a Black Hole Yields Tantalizing Evidence of an Event Horizon
1. What is an event horizon, and how do astronomers know it exists?
An event horizon is the mysterious region surrounding a black hole that forever traps light and matter straying nearby. No astronomical object other than a black hole can possess an event horizon. Black holes have been inferred by observing the furious whirlpool motion of trapped gas and estimating how much mass is crammed into the tiny region of space the black hole occupies.
Previous X-ray observations have offered evidence for an event horizon by surveying black hole candidates that seem to be swallowing nearly 100 times as much energy as they radiate. Those results imply that trillion-degree gas is falling over the brink of an event horizon, like water over the edge of a waterfall. Until this Hubble observation, no telescope had ever detected what actually happens to a piece of matter swirling into the event horizon, like water down a drain.
2. Did the Hubble telescope see an event horizon?
Hubble didn't see the event horizon -- it is too small and too far away. The telescope did, however, measure chaotic fluctuations in ultraviolet light from seething gas trapped in orbit around the black hole. Hubble found two examples of a so-called "dying pulse train," the rapidly decaying, sequential flashes of light from a hot blob of gas spiraling into the black hole.
This signature matches theories of what scientists would predict to see when matter is falling so close to the event horizon that its light rapidly dims as it is stretched by gravity to ever-longer wavelengths
The Hubble telescope may have, for the first time, provided direct evidence for the existence of black holes by observing how matter disappears when it falls beyond the "event horizon," the boundary between a black hole and the outside universe. Astronomers found their evidence by watching the fading and disappearance of pulses of ultraviolet light from clumps of hot gas swirling around a massive, compact object called Cygnus XR-1. This activity suggests that the hot gas fell into a black hole.
Lone Black Holes Discovered Adrift in the Galaxy.
Astronomers using the Hubble telescope and ground-based observatories have discovered the first examples of isolated, stellar-mass black holes adrift among the stars in our Milky Way Galaxy. They detected two of these lonely, invisible objects indirectly by measuring how their extreme gravity bends the light of a more distant star behind them.
All previously known "stellar" black holes have been found orbiting normal stars. Astronomers determined the presence of those compact powerhouses by examining their effect on their companion star. These new results suggest that black holes are common and that many massive but normal stars may end their lives as black holes instead of neutron stars, the crushed cores of massive stars that end their lives in supernova explosions.
The findings also suggest that stellar-mass black holes do not require some sort of interaction in a double-star system to form but may be produced in the collapse of isolated, massive stars, as has long been proposed by stellar theorists.
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Post by Toxic-Avenger on Jul 17, 2002 12:56:09 GMT -5
Black Holes, continued. 1. What are stellar-mass black holes, and how are they different from supermassive black holes? Stellar-mass black holes are the compressed remains of giant, exploding stars called supernovas. These compact, gravitational powerhouses keep everything, including light, from escaping their stranglehold. Supermassive black holes, as their name implies, are monsters. They are millions to billions of times more massive than the Sun and are believed to reside at the hearts of most galaxies. Scientists aren't sure how they first formed, but they believe that these massive "eating machines" were created during the early universe. Stellar-mass black holes, on the other hand, can form at any time. Supermassive black holes are easier to detect because scientists know where to look: the centers of galaxies. All black holes, by their very nature, are invisible. But scientists hunting for supermassive black holes probe the centers of galaxies, looking for how the suspected monsters gravitationally influence the stars and dust near the cores. 2. Explain the technique astronomers use to find the "drifting" stellar black holes. The black hole's gravity acts like a powerful lens, bending the light of a background star, so that it appears as two separate images when the black hole slowly drifts in front of it. However, the black hole's gravity also magnifies these stellar images, causing them to brighten as the black hole passes in front. Astronomers used ground-based telescopes to search for these passages, called gravitational "microlensing" events. The two pictures at left identify the brightening star for one of the black holes. They then tapped Hubble and its sharp vision to pinpoint the "lensed" star. The Hubble frame [picture at right] indicates that the lensed star was blended with two neighboring stars of similar brightness that could not be separated in the poorer-resolution, ground-based images. Hubble's identification of the lensed star allowed for an accurate estimate of the mass of the black hole. 3. If astronomers can't see the objects passing in front of the stars, how do they know they're black holes? Careful analysis reveals that each black hole is approximately six times the mass of the Sun. If they were ordinary stars with this bulk they would be bright enough to outshine the more distant background star. The masses are also too large to be white dwarfs or neutron stars. This leaves a black hole as the most likely explanation. Here's a good picture of a black hole at the center of the Circinus galaxy. See text for explanation below \/ Circinus Galaxy-Optical Much of the gas in the disk of the Circinus spiral is concentrated in two specific rings -- a larger one of diameter 1,300 light-years another with a diameter of 260 light-years. In the Hubble image, the smaller inner ring is located on the inside of the green disk. The larger outer ring extends off the image and is in the plane of the galaxy's disk. This Hubble Space Telescope image of the Circinus Galaxy was taken on April 10, 1999 with the Wide Field Planetary Camera 2. (Credit: NASA/A.Wilson et al.) A Cosmic Searchlight 1. How does the black hole create the jet? The jet originates in the disk of superheated gas swirling around this black hole and is propelled and concentrated by the intense, twisted magnetic fields trapped within this matter. The light we see is produced by electrons twisting along magnetic field lines in the jet, a process known as synchrotron radiation, which gives the jet its bluish tint.
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Post by It's~A~Nova on Sept 15, 2002 13:12:06 GMT -5
I saw this article today and thought I'd post it~
Voracious Black Holes Detected in Old Galaxies By Deborah Zabarenko
WASHINGTON (Reuters) - Old galaxies huddled together in clusters were once dismissed as the rest homes of the cosmos, but scientists reported on Friday that many of them have massive black holes gobbling gas at their cores.
The discovery of active black holes where none was suspected means these massive matter-sucking drains in space may be even more common than astronomers first thought.
It also indicates that even the oldest galaxies are not necessarily as staid as they may first appear.
"Most of these galaxies are really old and we've always though they weren't doing much for a long time," said Dan Kelson of the Carnegie Observatories in Pasadena, California. "They're actually a lot more active than we've really thought."
In some cases, Kelson said by telephone, these galaxies may be as much as 10 billion years old, more than two-thirds the suspected age of the universe. Unlike younger galaxies, the black holes in the galaxies in galactic clusters were thought to be quiescent, with nothing to "eat" and therefore no way for scientists to detect them.
Black holes are celestial objects whose gravity is so great that nothing, not even light, can escape. That makes them invisible but astronomers know where they are because of the swirling gas and dust that circles their rims just before being sucked into the hole.
Using NASA's orbiting Chandra X-Ray Observatory and the ground-based Walter Baade optical telescope in Chile, scientists discovered six active black holes in galaxy cluster Abell 2104, where they suspected only one.
An image is available online at http:/www.carnegieinstitution.org/carnegieobservatories.
The key, Kelson said, was using the X-ray observatory, which can peer through gas and dust to detect the X-rays being emitted from the intense friction that results as matter is pulled into the black hole.
A black hole's gulp -- the period when it emits X-rays -- lasts maybe 1 million years or so, an eye-blink on the cosmic time scale, Kelson said.
"If we actually saw five or six of these in a cluster of 1,000 galaxies, that actually means that we just happened to look during the right period where those five or six are on," he said.
"That means all of the galaxies of this cluster have been turning on and off -- they turn on when they get more gas to swallow," he said. "They've probably all been turning on and off, which means that these giant black holes ... really are everywhere, every galaxy must have these things."
Galaxy clusters contain hundreds to thousands of galaxies, often old, reddish elliptical galaxies distinct from blue, spiral galaxies like the Milky Way, which contains Earth. These old galaxies also do not have many young stars and not much interstellar dust, prime fuel for black holes.
Astronomers now must try to figure out what makes these old black holes turn on again, Kelson said.
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Post by Toxic-Avenger on Sept 18, 2002 9:28:38 GMT -5
Very cool article Completley.Incomplete, thanks. That link didn't work, here it is again. www.carnegieinstitution.org/carnegieobservatories/And here's another article from MSNBC. A middleweight black hole in the midst of a globular star cluster. Present-day telescopes can't see black holes directly; instead, they are detected by their gravitational influence. NASA's Anne Kinney explains where a black hole was detected in the globular cluster M15, using zoom-in views from Hubble and a dramatic animation. By Robert Roy Britt SPACE.COM Sept. 17 — Astronomers said Tuesday that they’ve firmly identified two medium-mass black holes, supplying strong confirmation that these curious middleweights exist. BLACK HOLES cannot be seen, and so they have to be detected by observing the environment around them. Scientists are convinced of the presence of so-called stellar black holes that result from the collapse of a single star, as well as galaxy-anchoring supermassive black holes weighing as much as billions of stars. Previous observations, particularly by the Chandra X-Ray Observatory, have suggested that there are in-between objects — black holes that are tens, hundreds or perhaps thousands of times as massive as the stellar variety. But theorists worried that these might be stellar black holes masquerading as more weighty objects. Two new studies, based on data from the Hubble Space Telescope, each found a middleweight in the unexpected environment of an ancient star cluster. These globular clusters, as they are called, are thought to contain the oldest stars of the universe. They are densely packed but relatively quiescent places — unlike the chaotic regions near the centers of galaxies that contain supermassive black holes. Researchers involved in the studies say that globular clusters probably had black holes early in their histories and that they might fill a missing link in the understanding of how their far more massive cousins develop. ‘BUILDING BLOCKS’<br>“The intermediate-mass black holes that have now been found with Hubble may be the building blocks of the supermassive black holes that dwell in the centers of most galaxies,” said Karl Gebhardt of the University of Texas at Austin. Gebhardt worked on a team led by Michael Rich of the University of California at Los Angeles, which found a black hole 20,000 times the mass of our sun in a globular cluster called G1. The cluster is 2.2 million light-years from Earth and is part of the Andromeda Galaxy.
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Post by Toxic-Avenger on Sept 18, 2002 9:29:23 GMT -5
Black Holes, Part Two Another team, led by Roeland Van Der Marel of the Space Telescope Science Institute in Baltimore, detected a black hole about 4,000 times the sun’s mass. It sits in the center of a globular cluster called M15, roughly 32,000 light-years away and within our own Milky Way galaxy.
The Space Telescope Science Institute manages Hubble for NASA. “These findings may be telling us something very deep about the formation of star clusters and black holes in the early universe,” Van Der Marel said. “Black holes are even more common in the universe than previously thought.” BLACK HOLE ‘SEEDS’? Theorists are still trying to understand how black holes form. One idea is that they develop all at once when a galaxy forms. Another method might be that a black hole “seed” is created and grows over time. “The Hubble results add new credibility to the latter scenario,” Van Der Marel said.
Globular clusters, being old, are like a snapshot of an earlier time. Because they have black holes and probably have had them since early on, they are now seen as good candidates for the “seeds” that theorists have been looking for, researchers from both teams agreed.
An interesting aspect to the discovery is that the newfound black holes pack the same percentage of mass relative to their host star clusters as do supermassive black holes in relation to their host galaxies. This fraction, about 0.5 percent, appears to suggest some underlying process for black hole formation and evolution, the researchers said. LOOKING IN CLUSTERS Astronomers have hunted for black holes in globular clusters for nearly three decades, but ground-based visible-light observations can’t resolve the central dense regions of stars well enough to see what all is there. Hubble was used to examine the velocity of stars relative to each cluster as a whole, data that revealed the presumed black holes, explained Rutgers University researcher Carlton Pryor, who worked on the M15 discovery. Unlike a typical galaxy in which most stars are arranged in a single, rotating disk, the stars in a globular cluster are set up in a spherical pattern.
“It would look like a swarm of gnats,” Pryor said in a telephone interview. “The motions are every which way.” A large amount of mass hidden in the cluster’s center is needed to explain the high speeds of the stars, Pryor said. While the central mass is presumed to be a black hole, researchers can’t completely rule out other possible explanations, such as a collection of dense neutron stars.
The M15 observations were made three years ago and required painstaking analysis to reach the conclusions, announced at a NASA press conference Tuesday.
The presumed black hole in G1 was found using a similar technique. Because that cluster is so far away, however, researchers looked at the combined light of the cluster and inferred from it the velocities of stars. The globular cluster M15 is visible in binoculars. G1 is a tougher target, requiring a good-sized amateur telescope. © 2002 Space.com. All rights reserved.
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