Space 'Hurricane' Blowing At 450,000 MPH Heavy Elements Found In Wind From Distant Galaxy Emil Venere ----------------------------------- Homewood News and Information Astronomers have discovered a galaxy-size "hurricane" blowing gas at speeds of 450,000 miles per hour--providing one possible explanation for a cosmic mystery. Chemical elements such as carbon, nitrogen, oxygen and iron are produced inside stars and dispersed in space when stars explode. These "heavy elements" are deposited in regions near stellar explosions; how then, could they be found in the space between galaxies, where there are few, if any, stars? The "superwind," speeding out from the center of a galaxy 86 million light-years away, is offering a clue. "This tells you that, at some moment in the evolution of the galaxy, you can have an event that blows out away from the galaxy a significant amount of enriched gas," said Zlatan Tsvetanov, an associate research scientist in the Department of Physics and Astronomy. "This would be a powerful way to enrich the gas with heavy elements, at least in the relatively immediate surroundings of the galaxy." The ionized gas is streaming out from the center of a galaxy in the southern sky called NGC 2992. It is speeding away in the shape of two cones, or bowls, one from either side of the galaxy's center, extending more than 20 kiloparsecs, or 62,000 light-years, from the galaxy's core. "The gas blows away from the galaxy, in each direction, just like a very strong wind," Tsvetanov said. "That's why I called it a hurricane." The wind probably originates somewhere in the center of the galaxy, but astronomers aren't sure what the driving force is. One possibility is a powerful starburst--the simultaneous birth of many stars--which releases a tremendous amount of energy. Another possibility is that NGC 2992 might be a Seyfert galaxy, a type of galaxy that has an exceptionally bright, compact center producing as much light as an entire normal galaxy of stars, suggesting the presence of a massive black hole in the nucleus. A black hole could produce the enormous energy required to drive the wind, Tsvetanov said. The Hopkins astronomer, along with Professor Michael Dopita and graduate student Mark Allen, both from Australian National University, wrote a scientific paper on the research, which was presented June 14 during a meeting of the American Astronomical Society in Pittsburgh. NGC 2992 is about the size of the Milky Way. It contains a huge mass and produces a powerful gravitational attraction. That means a huge amount of energy would be needed to drive the gas away from the galaxy at such high speeds seen in the superwind. Astronomers think NGC 2992 is a spiral galaxy, like the Milky Way. But they can't be sure, because the galaxy does not face the Earth; astronomers see it edgewise, which makes it possible to observe the two cones of superwind extending from each side of the galaxy's disk. The astronomers used spectrographs and cameras on three telescopes to observe the galaxy: the Anglo-Australian telescope and the ANU 2.3-meter Advanced Technology Telescope, both at Siding Springs, Australia, and the New Technology Telescope at the European Southern Observatory in La Silla, Chile. The superwind's gas is highly ionized--its atoms have been stripped of many of their electrons by powerful radiation. Astronomers viewed the galaxy through two filters, enabling them to isolate gas in particular ionization states at numerous positions across regions of gas. "We basically mapped the region with spectroscopy," Tsvetanov said. By making precise spectrographic measurements of the radiation emitted by the gas, the scientists were able to calculate how fast the gas is moving. The wind is speeding at 150 to 200 kilometers per second (335,000 to 450,0000 mph) in either direction from the galaxy's center.
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