Black Holes -the Reality & the Fiction
A report is out that NASA’s Chandra observatory has captured piranha-like, supermassive black holes devouring matter in young galaxy clusters. However, many of us are left wondering about last month’s news that black holes aren’t even real. So what’s really going on here?
It seems that the widely circulated stories that black holes do not exist are probably a bit bogus. More than anything, the reports (largely based on work by Tanmay Vachaspati and his colleagues at Case Western Reserve University in Cleveland) are a name-game, which argues that black holes are really “black stars” without true event horizons.
Most theoretical physicists dispute Vachaspati’s claim. Nobel laureate Gerard 't Hooft of Utrecht University in the Netherlands said, "The process he describes can in no way produce enough radiation to make a black hole disappear as quickly as he is suggesting." In other words, the horizon forms long before the hole can evaporate. Whichever the case, for general purposes if something looks a black hole and acts like a black hole, then for all intents and purposes—it’s still going to be called a black hole. However, scientists will likely continue to debate their distinct features many years into the future.
As far as the supermassive gobblers go, it’s important to point out that most theoretical theorists believe that the popular conception of black holes as "sucking" things in is false. Objects can maintain an orbit around black holes indefinitely provided they stay outside the photon sphere. The common theory about blacks holes is that they have a gravitational field so powerful that a region of space basically becomes cut off from the rest of the universe, and that no matter that has entered the region can ever escape. It is this lack of escaping electromagnetic radiation that renders the inside of black holes (beyond the event horizon) invisible, which is why they are called “black holes”. Accordingly, no one has really ever seen the center of one and they are detectable only as they interact with outside matter.
The two particular “gigantic gobblers” detected by Chandra are rapidly growing black holes, also known as active galactic nuclei (AGN). The data showed, for the first time, that younger and more distant galaxy clusters contain far more AGN than older, nearby ones.
It is suspected that the reason for the difference is that earlier in the history of the Universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. There was so much fuel in young clusters that the piranha-like black holes were able to thrive by growing much earlier than their counterparts in nearby clusters. The researchers say that the black holes gorge on the plentiful gas until little fuel is left, and then they fade away. In actuality, the black hole is still there but the activity diminishes as the gases that it “feeds on” become scarcer.
An average-sized galaxy contains about 100 billion stars, and a single galaxy cluster contains several hundred galaxies. However, only a few of the cluster's galaxies contain AGN.
It is interesting to note that stars, black holes, galaxies and galaxy clusters sometimes crash and merge with one another. When galaxy clusters collide, the amount of energy generated would be second to only to the theoretical Big Bang event that many scientists believe gave birth to the universe.
Posted by Rebecca Sato
Related Galaxy posts:
Andromeda Galaxy & Its Mystery Core: Destined to Merge With the Milky Way?
It is called "black" hole since the hole did not exist
Posted by: james | July 30, 2007 at 04:52 AM