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Science North Star dims for a century, suddenly gets brighter
Science North Star dims for a century, suddenly gets brighter | North Star dims for a century, suddenly gets brighter |
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| by William Atkins | |
| Wednesday, 23 July 2008 | |
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Page 2 of 3 One of these two small telescopes was the U.S. Navy/U.S. Air Force’s Coriolis satellite, launched in January 2003, which Dr. Penny was using through its SMEI (Solar Mass Ejection Imager) space camera. Featured Whitepaper
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Science DiscussionsPenny said: "One hundred years ago Polaris varied by 10%, but over the last century the variations became smaller and smaller until 10 years ago it only varied by 2%. It was thought the structure of the star was changing to switch off the vibration. Yet the team has found that about 10 years ago the vibrations started picking up and are now back up at the 4% level." The abstract to the paper states, “Measurements of the amplitude of the dominant oscillation (P = 4 days), that go back more than a century, show a decrease from 120 mmag to 30 mmag (V magnitude) around the turn of the millennium.” With Polaris now brightening, astronomers are not sure how to explain this reversal. They stated that the slow decline in the brightness of Polaris was “in itself unusual, as no other Cepheid is known to do this.” Now that it is growing brighter, the actions of Polaris are even stranger for astronomers. They are now considering that Polaris, like other aging star, may have a complex process working in their outer layers that is not known by astronomers. Visible only in the northern hemisphere, Polaris is 430 light-years from Earth, where one light-year is the distance that light (radiation) travels in the vacuum of space over the course of one Earath-year. Polaris is called the North Star because it lies very near to the north celestial pole on Earth. Thus, Polaris appears to lie directly overhead to someone at the Earth's North Pole. It lies about two-thirds of one degree from the North Pole, so does take a tiny bit of motion around the pole. Polaris is located (as seen in the northern hemisphere on Earth) at the end of the "bob" of the Little Dipper in the constellation Ursa Minor. A paper based on the research of this international team of astronomers will be published in the August 10, 2008 edition of the Astrophysical Journal. A pre-publication paper called “Polaris the Cepheid returns: 4.5 years of monitoring from ground and space” is found on the arxiv.org website. Its authors are H. Bruntt, N. R. Evans, D. Stello, A. J. Penny, J. A. Eaton, D. L. Buzasi, D. D. Sasselov, H. L. Preston, E. Miller-Ricci. The abstract to their paper is found on page three. |
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