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RE: Mira AB
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Astronomers generally assume that the dusty disks where planets form are found around young stars in stellar nurseries. Now, for the first time, a protoplanetary disk has been found in the environment of a dying star.
A team of astronomers is reporting today at the winter meeting of the American Astronomical Society that material from the dying star Mira A is being captured into a disk around Mira B, its companion. Michael Ireland of the California Institute of Technology and his coauthors, John Monnier from the University of Michigan, Peter Tuthill from the University of Sydney, and Richard Cohen from the W.M. Keck Observatory, say that the finding implies that there should be many similar undiscovered systems in the solar neighbourhood, providing a myriad of new places to look for young extrasolar planets.
Located 350 light years away in the constellation of Cetus, Mira (christened the “Miracle star”) first shook the foundations of the astronomy world 400 years ago with its changing brightness: visible to the naked eye for about 1 month at a time, becoming 1,000 times fainter and disappearing from view, only to re-appear again on an 11 month cycle.

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Mira
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Credit: Michael Ireland, Caltech

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Mira A (right), a highly evolved red giant star, and Mira B (left), a white dwarf, was imaged by the Chandra x-ray telescope, and shows Mira A losing gas rapidly from its upper atmosphere, via a stellar wind, and Mira B exerting a gravitational tug that creates a gaseous bridge between the two stars.
Gas from the wind and bridge accumulates in an accretion disk around Mira B and collisions between rapidly moving particles in the disk produce X-rays.
Mira A (or simply, Mira) was named "The Wonderful" star in the seventeenth century because its brightness was observed to wax and wane over a period of about 330 days. In this advanced red giant phase of Mira A's life, its diameter has swollen to about 600 times that of the Sun and it is pulsating, due to increasingly energetic nuclear reactions in its core.
Mira A is now approaching the stage where its nuclear fuel supply will be exhausted, and it will collapse to become a white dwarf. In contrast, Mira B has already reached the white dwarf stage, and is about the size of the Earth, but about a half million times more massive.
The stars in Mira AB are about twice as far apart as Pluto is from the Sun.
The star system is about 420 light years away in the constellation Cetus.
Position (J2000) RA 02h 19m 20.70s Dec -02° 58' 39.51

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-- Edited by Blobrana at 19:51, 2005-04-28

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