6,309 research outputs found
The tails in the Helix Nebula NGC 7293
We have examined a stream-source model for the production of the cometary
tails observed in the Helix Nebula NGC 7293 in which a transonic or moderately
supersonic stream of ionized gas overruns a source of ionized gas. Hydrodynamic
calculations reveal velocity structures which are in good agreement with the
observational data on tail velocities and are consistent with observations of
the nebular structure. The results also are indicative of a stellar atmosphere
origin for the cometary globules. Tail remnants persist for timescales long
enough for their identification with faint striations visible in the nebula gas
to be plausible.Comment: 7 pages, 6 figures, accepted for publication in A&
The Space Telescope Observatory
A convenient guide to the expected characteristics of the Space Telescope Observatory for astronomers and physicists is presented. An attempt is made to provide enough detail so that a professional scientist, observer or theorist, can plan how the observatory may be used to further his observing programs or to test theoretical models
Impact for Agents
Impact for agents. Most of the agent research community has been predicting greater impact for years and many of us have been working to help the process along. Yet the tremendous growth on the research front has not been met with
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