Results 81 to 90 of about 23,039 (206)
Close Binaries and the Abundance Discrepancy Problem in Planetary Nebulae
Galaxies, 2018 Motivated by the recent establishment of a connection between central star binarity and extreme abundance discrepancies in planetary nebulae, we have carried out a spectroscopic survey targeting planetary nebula with binary central stars and previously ...
R. Wesson +4 more
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Molecules in planetary nebulae [PDF]
The Astrophysical Journal, 1978 The study of molecules in planetary nebulae is still in its infancy; therefore, it is appropriate both to review existing knowledge and to anticipate developments that will arise as the subject matures. Briefly stated, this subject consists of observations of hydrogen, H2, and carbon monoxide, CO, molecules in a very few nebulae; the tentative ...
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Evaluating Investment in Space Programs: A Case for Theoretical Pluralism
Financial Accountability &Management, Volume 42, Issue 1, Page 19-35, February 2026.ABSTRACT A perennial question repeatedly asked since the early Mercury (USA) and Salyut (then Soviet Union) space programs has been variations on the theme of “how can the cost of space exploration be justified?” This question—which in broad terms constitutes the research question considered in this paper—continues to be directed toward space agencies ...
Basil P. Tucker, Hank C. Alewine
wiley +1 more source
Whither or Wither the Sulfur Anomaly in Planetary Nebulae?
The Astrophysical Journal LettersWe present a thorough investigation of the long-standing sulfur anomaly enigma. Our analysis uses chemical abundances from the most extensive data set available for 126 planetary nebulae (PNs) with improved accuracy and reduced uncertainties from a 10° ×
Shuyu Tan, Quentin A. Parker
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Testing the binary hypothesis for the formation and shaping of planetary nebulae
, 2012 There is no quantitative theory to explain why a high 80% of all planetary nebulae are non-spherical. The Binary Hypothesis states that a companion to the progenitor of a central star of planetary nebula is required to shape the nebula and even for a ...
Bojicic, I. +7 more
core
A Dedicated Camera For Extragalactic Planetary Nebulae: The Planetary Nebula Spectrograph [PDF]
Symposium - International Astronomical Union, 1997 Photometry in [OIII] emission of Planetary Nebulae in external galaxies can be used to determine distances as great as that of the Virgo cluster and beyond, as forcefully argued elsewhere during this conference (G.H. Jacoby, invited talk). In addition, measurement of the radial velocities of the PN allows dynamical behaviour to be probed to much ...
Douglas, NG +3 more
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New Close Binary Central Stars of Planetary Nebulae from Gaia DR3 Epoch Photometry. [PDF]
Res Notes AAS, 2022 Chornay N, Walton NA.
europepmc +1 more source
Planetary Nebulae: An Introductory Review [PDF]
Symposium - International Astronomical Union, 1983 Planetary nebulae constitute a popular field of investigation because they offer a unique opportunity to study the final stages of stellar evolution before a star dies. They supply challenges not only to the stellar evolution expert but also to the spectroscopist, to the student of galactic structure, and to all observers, whether one works in the ...
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On the Origin of Morphological Structures of Planetary Nebulae
Galaxies, 2018 We suggest that most of the mass in planetary nebulae (PNe) resides in the equatorial region and the spherical envelope and the optically bright lobes of PNe are in fact low-density cavities cleared out by fast outflows and photoionized by UV photons ...
Sun Kwok
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Molecular Envelopes of Planetary Nebulae and Proto-Planetary Nebulae [PDF]
International Astronomical Union Colloquium, 1994 As stars evolve up the asymptotic giant branch (AGB), they begin to lose mass at a high rate, and in the process they create extended circumstellar molecular envelopes. Since the transition from AGB to planetary nebula stages is of the order of 1000 yr, the remnant of such molecular envelopes should still be observable in pro to-planetary nebulae (PPN)
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