Feb. 19, 2009 -- The effects of a small galaxy colliding with our own almost two billion years ago are still being felt, say an international team of astronomers. Their findings, which appear on the pre-press physics Web site arXiv, explain why the Milky Way is vibrating, or "ringing," and why stars in it are clustering together. Astronomers have known for almost a decade that the Milky Way is ringing, said Ken Freeman of the Research School of Astronomy and Astrophysics at the Australian National University. They have suspected the ringing was caused by a bar-like structure in the center of the galaxy. "In the center of our galaxy is a bar-like structure that is quite massive," he said. "Because it's not round its gravitational field is not round, so you get a certain kind of resonance between the bar and the stars that are moving." Related Content: But Freeman and colleagues have now shown, through mathematical modelling, that a major cause of the galactic ringing was a collision by a small galaxy that occurred 1.9 billion years ago. Like a stone dropping into a pond, the collision resulted in vibrations that set up a resonance in the Milky Way and caused stars to group into clusters. Freeman said clusters of stars can occur during star formation. They also can form when a small galaxy is sucked into our own, broken up into pieces and its debris spread around. He said it is important to "weed out" the clusters that form as a result of the ringing, in order to determine the formation of the Milky Way. "It's pretty important to work out which one of these is which, if we want to try and trace what has happened in the galaxy over the years," he said. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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