scholarly journals Small-scale structures in planetary nebulae

2017 ◽  
Author(s):  
◽  
Sean P. Baldridge
Keyword(s):  
Molecular Hydrogen ◽  
Planetary Nebulae ◽  
Small Sample ◽  
Molecular Structures ◽  
Small Scale ◽  
Hydrogen Emission ◽  
Scale Structures ◽  
Research Challenge ◽  
Ring Nebulae ◽  
Small Scale Structures

Two planetary nebulae (PNe) were studied in order to investigate small scale molecular structures in planetary nebulae, the survival of which affects the structure and composition of the interstellar medium (ISM) from which the next generation of stars is born. Molecular hydrogen (H[subscript 2]) was used a tracer for molecular emission and its excitation properties used as a probe of shock physics. Previous studies of several planetary nebulae have indicated a relationship between molecular hydrogen and cometary knots as a shielding mechanism allowing for continued survival and formation of the molecule. Our first PN studied, the Dumbbell nebula (NGC 6853), revealed not only H[subscript 2] bearing knots (similar to the Helix and Ring nebulae), but also regions of H[subscript 2] emission which were poorly sculpted or unstructured diffuse regions, unlike previously studied nebulae. The second PN, NGC 2392 has well documented cometary knots, however we find no detection of molecular hydrogen emission from the knots or otherwise making it an outlier among cometary knot bearing planetary nebulae. Both nebula studied in this research challenge current models of H[subscript 2] bearing small scale structures in PNe and indicate a need to expand our rather small sample of such objects so that we may begin to understand the processes behind H[subscript 2] formation, excitation, and its role in cometary knots of the PN as a whole.

scholarly journals Sub-Arcsecond Morphology of Planetary Nebulae

2010 ◽  
Vol 27 (2) ◽  
pp. 180-186 ◽  
Author(s):  
L. F. Miranda ◽  
G. Ramos-Larios ◽  
M. A. Guerrero
Keyword(s):  
Narrow Band ◽  
Planetary Nebulae ◽  
Small Scale ◽  
High Quality ◽  
Fine Structures ◽  
Scale Structures ◽  
Small Scale Structures

AbstractPlanetary nebulae (PNe) can be roughly categorized into several broad morphological classes. The high quality images of PNe acquired in recent years, however, have revealed a wealth of fine structures that preclude simplistic models for their formation. Here we present narrow-band, sub-arcsecond images of a sample of relatively large PNe that illustrate the complexity and variety of small-scale structures. This is especially true for bipolar PNe, for which the images reveal multi-polar ejections and, in some cases, suggest turbulent gas motions. Our images also reveal the presence or signs of jet-like outflows in several objects in which this kind of component has not been previously reported.

scholarly journals Molecular envelopes of young and proto PNe

1997 ◽  
Vol 180 ◽  
pp. 151-160
Author(s):  
S. Deguchi
Keyword(s):  
Planetary Nebulae ◽  
Small Scale ◽  
Scale Structures ◽  
Small Scale Structures

I review recent results of mm-wave interferometric observations of molecular envelopes of young and proto planetary nebulae. Spatial resolutions of mm-wave interferometers now reach from one to a few arcseconds; together with line observations reveale very small structures in molecular envelopes of planetary nebulae. These small scale structures are probably caused by an instability of the radiation-driven, gas-dust outflow. Implications of these observations and theories are discussed.

Exploring Coronal Structures with SOHO

2000 ◽  
Vol 179 ◽  
pp. 403-406
Author(s):  
M. Karovska ◽  
B. Wood ◽  
J. Chen ◽  
J. Cook ◽  
R. Howard
Keyword(s):  
Solar Corona ◽  
Image Enhancement ◽  
Coronal Mass Ejections ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Low Contrast ◽  
Contrast Structures ◽  
Scale Structures ◽  
Small Scale Structures ◽  
Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

scholarly journals Observational aspects of prominence oscillations

2007 ◽  
Vol 3 (S247) ◽  
pp. 152-157 ◽  
Author(s):  
Oddbjørn Engvold
Keyword(s):  
Magnetic Structure ◽  
Numerical Models ◽  
Small Scale ◽  
Solar Prominences ◽  
Scale Structures ◽  
Oscillations And Waves ◽  
Available Information ◽  
Small Scale Structures

AbstractSeismology has become a powerful tool in studies of the magnetic structure of solar prominences and filaments. Reversely, analytical and numerical models are guided by available information about the spatial and thermodynamical structure of these enigmatic structures. The present invited paper reviews recent observational results on oscillations and waves as well as details about small-scale structures and dynamics of prominences and filaments.

scholarly journals Detailed maps of interstellar clouds in front of ω Centauri: small-scale structures in the Galactic disc-halo interface

2009 ◽  
Vol 399 (1) ◽  
pp. 195-208 ◽  
Author(s):  
Jacco Th. van Loon ◽  
Keith T. Smith ◽  
Iain McDonald ◽  
Peter J. Sarre ◽  
Stephen J. Fossey ◽  
...  
Keyword(s):  
Small Scale ◽  
Galactic Disc ◽  
Interstellar Clouds ◽  
Scale Structures ◽  
Small Scale Structures

scholarly journals Stationary magnetospheric convection on November 24, 1981. 2. Small-scale structures in the dayside cusp/cleft

1999 ◽  
Vol 17 (3) ◽  
pp. 375 ◽  
Author(s):  
Y. I. Galperin ◽  
J. M. Bosqued ◽  
R. A. Kovrazhkin ◽  
A. G. Yahnin
Keyword(s):  
Small Scale ◽  
Magnetospheric Convection ◽  
Scale Structures ◽  
Small Scale Structures
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