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Just when you think you know what's happening...
Recent observations in the constellation Leo, using NASA's SWIFT satellite, which contains three unique wavelength telescopes, has scientists re-writing the text books on black holes.
A black hole is the mysterious object formed by the death of a very large star. Our Sun is an average sized star, known as a main sequence yellow star. When it finally uses up all it's fuel, in about 5.5 billion years, it will become a very cold, very small, very dense remnant of itself called a white dwarf star. Because it is so dense, this white dwarf will have a very powerful gravitational field. The larger a star is when it dies, the denser the leftover remnant becomes, and the more powerful the gravity. When a very large star dies, the remnant at its core becomes so dense that the molecules cannot be crushed together any tighter - and something magical happens. It disappears.
Not only does it disappear, but anything anywhere near it also disappears. This is due to the overwhelming power of its gravity. Gravity so powerful that not even light can escape it. This remnant of a star becomes an invisible cosmic vacuum cleaner, sucking in anything within its reach. It becomes a black hole. The NASA illustration below depicts the whirling gravitational vortexes surrounding a black hole.
Until recently, the theory was that the formation of a black hole was preceded by a massive explosion. But the advanced technology of the telescopes on the SWIFT satellite has allowed scientists to actually witness the birth of black holes, and they have discovered that their birth is preceded by not one, but two or three, and sometimes four explosions! This means that the whole idea of the neat, orderly birth of a black hole is out the window. One of the scientists involved, Prof. Peter Meszaros of Penn State, summed it up this way: "We aren't clear on the details yet, but it appears to be messy."
And while we try to figure out how black holes are formed, there are even more intriguing questions that beg answers. Like: Where does everything go, after it gets sucked into a black hole? And: Do time and space get sucked into a black hole as well? Feel free to let your imagination run wild. You may just be right!
For many years now, it has been mathematically hypothesized and generally accepted that most galaxies have a black hole at their centre. But so far only two galaxies have been directly proven to contain black holes: NGC 4258, and our own Milky Way Galaxy. Now, as of September 20, 2005, a third galaxy can be added to the list: M31, known as the Andromeda Galaxy, shown below.
Observing the heart of the Andromeda Galaxy with Hubble's Space Telescope Imaging Spectrograph (STIS), scientists found stars with an orbital velocity of 1,000 kilometers per second. The gravitational force needed to produce this type of velocity would require a mass equal to 140 million suns. Since the centre of the galaxy is dark, there is only one thing that could be there, producing that kind of gravity: a black hole.
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