Dark Matter and the Universe
December 4th 2007 08:09
In the beginning the Universe was young, it was almost smooth and featureless (sounds like a verse form the book of Genesis). As it grew older and developed, it became structured and eventually ordered.
We know that our solar system is organized into planets (including the Earth!) orbiting around the Sun. But our little corner of the universe is comparably small. On a much larger scale stars collect themselves into galaxies. Our Sun is an average star in an average galaxy called the Milky Way. The Milky Way contains about 100 billion stars. Yes, that's 100,000,000,000 stars! On still larger scales, individual galaxies are concentrated into groups, or what astronomers call clusters of galaxies.
The cluster includes the galaxies and any material which is in the space between the galaxies. The force, or adhesive, that holds the cluster together is gravity the mutual attraction of everything in the Universe for everything else. The space between galaxies in clusters is filled with a hot gas. In fact, the gas is so hot (tens of millions of degrees!) that it shines in X-rays instead of visible light. By studying the distribution and temperature of the hot gases we can measure how much it is being squeezed by the force of gravity from all the material in the cluster. This allows scientists to determine how much total material (matter) there is in that part of space.
Interestingly, it turns out there is five times more material in clusters of galaxies than we would expect from the galaxies and hot gas we can see. Most of the stuff in clusters of galaxies is invisible and, since these are the largest structures in the Universe held together by gravity, scientists conclude that most of the matter in the entire Universe is invisible. This invisible stuff is called 'dark matter' dark matter actually exists (who said watching Star trek wasn’t educational)
There is currently a great deal of research by scientists attempting to discover exactly what this dark matter is made up from, how much there is, and what effect it may have on the future of the Universe as a whole.
Images: NASA Hubble Telescope
We know that our solar system is organized into planets (including the Earth!) orbiting around the Sun. But our little corner of the universe is comparably small. On a much larger scale stars collect themselves into galaxies. Our Sun is an average star in an average galaxy called the Milky Way. The Milky Way contains about 100 billion stars. Yes, that's 100,000,000,000 stars! On still larger scales, individual galaxies are concentrated into groups, or what astronomers call clusters of galaxies.
Astronomers using NASA's Hubble Space Telescope have discovered a ghostly ring of dark matter that formed long ago during a titanic collision between two massive galaxy clusters Other galaxies can also bee seen in the distance
The cluster includes the galaxies and any material which is in the space between the galaxies. The force, or adhesive, that holds the cluster together is gravity the mutual attraction of everything in the Universe for everything else. The space between galaxies in clusters is filled with a hot gas. In fact, the gas is so hot (tens of millions of degrees!) that it shines in X-rays instead of visible light. By studying the distribution and temperature of the hot gases we can measure how much it is being squeezed by the force of gravity from all the material in the cluster. This allows scientists to determine how much total material (matter) there is in that part of space.
This is a new composite image of galaxy cluster MS0735.6 7421, located about 2.6 billion light-years away in the constellation Camelopardalis. The three views of the region were taken with NASA's Hubble Space Telescope in Feb. 2006, NASA's Chandra X-ray Observatory in Nov. 2003, and NRAO's Very Large Array in Oct. 2004. The Hubble image shows dozens of galaxies bound together by gravity.
Interestingly, it turns out there is five times more material in clusters of galaxies than we would expect from the galaxies and hot gas we can see. Most of the stuff in clusters of galaxies is invisible and, since these are the largest structures in the Universe held together by gravity, scientists conclude that most of the matter in the entire Universe is invisible. This invisible stuff is called 'dark matter' dark matter actually exists (who said watching Star trek wasn’t educational)
There is currently a great deal of research by scientists attempting to discover exactly what this dark matter is made up from, how much there is, and what effect it may have on the future of the Universe as a whole.
Images: NASA Hubble Telescope
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