And the Distance Is. . .

June 14, 2004 | It's official: the famous Veil Nebula in Cygnus is less than 1,900 light-years away. The wispy nebula is part of the extended Cygnus Loop — the remnant of a supernova that exploded between 5,000 and 8,000 years ago. In the past, astronomers assumed the Veil was at least 2,500 light-years away. But observations of NASA's Far-Ultraviolet Explorer (FUSE) now convincingly confirm earlier indications of a smaller distance obtained by the Hubble Space Telescope.

Five years ago, William P. Blair (Johns Hopkins University) combined existing line-of-sight velocity measurements of gaseous filaments in the Veil Nebula with Hubble estimates of the nebula's sideways expansion. By assuming the two speeds were equal, he derived a distance substantially smaller than 2,500 light-years. However, there was "considerable uncertainty" in the result, according to Blair.

Now, in a poster presentation at the American Astronomical Society meeting in Denver, Blair and his colleagues confirm the small distance. FUSE observations of a star known as KPD2055+311 revealed absorption lines in its spectrum indicating that it lies behind the Veil. From its observed properties, the team derives a distance of 1,860 light years for the star, so the Veil must be closer than that. According to team member Sharon I. Torres, this probably indicates a younger age for the supernova explosion than had been assumed before.

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