 Updated:2007-04-15 17:07:38
Dying Star Bursts in Near-Perfect Symmetry
By Ker Than
(April 12) -- If symmetry is a sign of splendor, then the newly discovered Red Square nebula is one of the most beautiful objects in the universe. Seen in the infrared, the nebula resembles a giant, glowing red box in the sky, with a bright white inner core. A dying star called MWC 922 is located at the system’s center and spewing its innards from opposite poles into space. (A nebula is an interstellar cloud of gas, dust and plasma where stars can both emerge and die.) “This spectacular event is the death of a star,” said study team member James Lloyd of Cornell University. After MWC 922 ejects most of its material into space, it will contract into a dense stellar corpse known as a white dwarf, shrouded by clouds of its own remains. The Red Square nebula discovery is detailed in the April 13 issue of the journal Science. Almost Perfect What is particularly astonishing about the Red Square, the researchers say, is the degree of symmetry seen in lines, or “rungs,” that bisect its surface. The rungs appear as shadows, and their makeup is uncertain. “The high degree of regularity in this case may point to the intriguing possibility that these bands are shadows cast by periodic ripples or waves on the surface of an inner disk close to the star at the heart of the system," Lloyd said. The Red Square ranks among the most symmetrical objects ever observed by scientists. “If you fold things across the principle diagonal axis, you get an almost perfect reflection symmetry,” said study leader Peter Tuthill from the University of Sydney in Australia. “This makes the Red Square nebula the most symmetrical object of comparable complexity ever imaged.” The Red Square’s extreme symmetry suggests the star’s surroundings are extremely still and not buffeted by external stellar winds or other turbulence. The researchers propose that similar conditions are contributing to the extreme symmetry of another system, the Red Rectangle, whose central star is cooler than that of the Red Square. “The Red Rectangle is mostly symmetrical, but it has some asymmetries,” Lloyd told SPACE.com. “It wasn’t clear whether it was because the outflow was very symmetrical or whether material in the outflow was encountering some other material” which introduced the symmetry. The new findings suggest the system’s perfect form results from an even outflow of gas. “The reason the Red Square remains so symmetrical is that there is no material that has interfered with the outflow, so it has preserved the symmetry it was born with,” Lloyd said. Tuthill and Lloyd spotted the Red Square using the 200-inch Hale Telescope at Caltech’s Palomar Observatory and the Keck-2 Telescope in Hawaii. Both telescopes utilize a relatively new type of imaging called adaptive optics, which uses a laser guide star as a reference and a rapidly deforming mirror to correct image distortions from the Earth’s atmosphere in real time. Adaptive optics “acts like a myopia cure for a telescope,” Lloyd said.
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