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Determination Of The Physical Conditions Of The Knots In The Helix Nebula From Optical And Infrared Observations, C. R. O'Dell, W. J. Henney, Gary J. Ferland
Determination Of The Physical Conditions Of The Knots In The Helix Nebula From Optical And Infrared Observations, C. R. O'Dell, W. J. Henney, Gary J. Ferland
Physics and Astronomy Faculty Publications
We use new Hubble Space Telescope and archived images to clarify the nature of the ubiquitous knots in the Helix Nebula, which are variously estimated to contain a significant to majority fraction of the material ejected by its central star. We employ published far-infrared spectrophotometry and existing 2.12 μm images to establish that the population distribution of the lowest rovibrational states of H2 is close to the distribution of a gas in local thermodynamic equilibrium at 988 ± 119 K. In addition, we present calculations that show that the weakness of the H2 0-0 S(7) line is not …