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Tantalizing hints of tiny, hard-to-see galaxies on the outskirts of our cosmic neighborhood may help astronomers solve a longstanding mystery.
Researchers recently reported dozens of candidate objects that could represent missing dwarf galaxies predicted by theory, but generally hidden from sight. One particularly promising gas ball shows signs of being a lost satellite of the Milky Way, scientists say.
The theory of dark matter — i.e. that much of the universe is made of invisible stuff that only interacts with normal matter via gravity — predicts that thousands of miniature clumps of dark matter should be orbiting our Milky Way galaxy and its neighbor, Andromeda. Many of these clumps should have also attracted gas to form stars that shine in visible light.
Yet of the thousands of dwarf galaxies predicted by theory, only 60 have been detected.
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http://www.space.com/14480-milky-missing-satellites-dwarf-galaxies.html
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Not since the work of Fritz Zwicky has the astronomy world been so excited about the missing mass of the Universe. His evidence came from the orbital velocities of galaxies in clusters, rotational speeds, and gravitational lensing of background objects. Now there’s even more evidence that Zwicky was right as Australian student – Amelia Fraser-McKelvie – made another breakthrough in the world of astrophysics.
Working with a team at the Monash School of Physics, the 22-year-old undergraduate Aerospace Engineering/Science student conducted a targeted X-ray search for the hidden matter and within just three months made a very exciting discovery. Astrophysicists predicted the mass would be low in density, but high in temperature – approximately one million degrees Celsius. According to theory, the matter should have been observable at X-ray wavelengths and Amelia Fraser-McKelvie’s discovery has proved the prediction to be correct.
Dr Kevin Pimbblet from the School of Astrophysics explains: “It was thought from a theoretical viewpoint that there should be about double the amount of matter in the local Universe compared to what was observed. It was predicted that the majority of this missing mass should be located in large-scale cosmic structures called filaments – a bit like thick shoelaces.”
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http://www.universetoday.com/85927/australian-student-uncovers-the-universes-missing-mass/#more-85927
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There's the common notion that black holes suck in everything in the nearby vicinity by exerting a strong gravitational influence on the matter, energy, and space surrounding them. But astronomers have found that the dark matter around black holes might be a different story. Somehow dark matter resists 'assimilation' into a black hole.
About 23% of the Universe is made up of mysterious dark matter, invisible material only detected through its gravitational influence on its surroundings. In the early Universe clumps of dark matter are thought to have attracted gas, which then coalesced into stars that eventually assembled the galaxies we see today. In their efforts to understand galaxy formation and evolution, astronomers have spent a good deal of time attempting to simulate the build up of dark matter in these objects.
Dr. Xavier Hernandez and Dr. William Lee from the National Autonomous University of Mexico (UNAM) calculated the way in which the black holes found at the center of galaxies absorb dark matter. These black holes have anything between millions and billions of times the mass of the Sun and draw in material at a high rate.
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http://www.universetoday.com/2010/03/22/astronomers-find-black-holes-do-not-absorb-dark-matter/
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