From the Hubble Space Telescope
Astronomers using NASA's Hubble Space Telescope have obtained the sharpest view yet of the Ring Nebula (M57), in the constellation Lyra, first cataloged more than 200 years ago by French astronomer Charles Messier. It is the best-known example of a planetary nebula, the glowing remains of a doomed star. The Ring is a cylinder of gas seen almost end-on. Such elongated shapes are common among planetary nebulae, because thick disks of gas and dust form a waist around a dying star. This "waist" slows down the expansion of the ejected material. The easiest escape route for this cast-off material is above and below the equator of the star.
Astronomers, however, have suspected for some time that the Ring Nebula has a cylindrical shape, but looks round only because of the viewing angle. Careful examination of the Hubble telescope image, taken by the Wide Field and Planetary Camera 2, strongly supports this opinion. The photo shows numerous small dark clouds of dust that have formed in the gas flowing out from the star, and are silhouetted against more distant bright gas. These dense dust clouds are too small to be seen with ground-based telescopes but are easily revealed by the Hubble telescope. Remarkably, these finger-like clouds are only seen in the outer portions of the Ring Nebula; none are in the central region. Thus they are not distributed in a uniform sphere but are instead located only on the walls of the barrel. Many of the finger-like clouds point away from the central star, like spokes on a wheel, due to the forces of radiation and gas ejected from the dying object.
Image Title: The Ring Nebula M57
based on press release for PHOTO NO.: STScI-PRC99-01
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Last Modified On: Tuesday, December 19, 2000