News Release Archive:

News Release 667 of 938

March 19, 1998 12:00 AM (EST)

News Release Number: STScI-1998-11

Hubble Captures the Shrouds of Dying Stars


Image: Planetary Nebula NGC 6818

Planetary Nebula NGC 6818

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NGC 6818 is in the constellation Sagittarius at a distance of about 6000 light-years. It has a diameter of about 0.5 light-year. The Hubble telescope observation was taken March 10, 1997 by the Wide Field and Planetary Camera 2.

This is a composite of images taken in 3 filters: Halpha is red, Hbeta is blue, and [O III] (doubly ionized oxygen) 5007 is green. As a result of the longer exposure time at Hbeta, the central star of the planetary nebula appears blue. We see a roughly spherical outer envelope as well as a brighter vase-shaped interior "bubble". Astronomers believe that a fast wind from the hot central star is creating the elongated shape and in fact has caused a "blowout" at the two ends of the major axis (lower right and upper left).

This nebula looks like a twin of NGC 3918, another planetary nebula (PN) that has been imaged by the Hubble telescope. The structure of NGC 3918 is remarkably similar to that of NGC 6818 - it has an outer spherical envelope, an inner brighter elongated bubble, and it also shows a blowout orifice at one end of the major axis in the bottom right-hand corner. By finding and studying such similar objects, it is hoped that crucial details can be learned about the evolutionary life history of planetary nebulae. One could call this "comparative PNology".

Object Name: NGC 6818

Image Type: Astronomical

Credits: Robert Rubin (NASA Ames Research Center), Reginald Dufour and Matt Browning (Rice University), Patrick Harrington (University of Maryland), and NASA


The above image is part of a montage:

Montage Image: Stellar Metamorphosis: Butterfly-Shaped Nebulae Emerge from Stellar Cocoons Image Type: Astronomical/Annotated Stellar Metamorphosis: Butterfly-Shaped Nebulae Emerge from Stellar CocoonsPRC1998-11b Cotton Candy Nebula (IRAS17150-3224) Image Type: Astronomical Cotton Candy Nebula (IRAS17150-3224) Silkworm Nebula (IRAS 17441-2411) Image Type: Astronomical Silkworm Nebula (IRAS 17441-2411) Planetary Nebula NGC 3918 Image Type: Astronomical Planetary Nebula NGC 3918

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