Abell 39

Planetary nebula


caption= Credit: WIYN/NOAO/NSF
name = Abell 39
type =
epoch = J2000
ra = RA|16|27|33.737Harvnb|SIMBAD|2008]
dec = DEC|+27|54|33.44
dist_ly = 6.8 kly (2.1 kpc)
appmag_v = Integrated: 13.7; Central Star: 15.5 ± 0.2
size_v = 155″.1 × 154″.5Harvnb|Jacoby|Ferland|Korista|2001]
constellation = Hercules
radius_ly = 2.5 ly (0.78 pc)Harvnb|APOD|2005]
absmag_v =
notes = Almost perfectly spherical
names = PN A66 39, PN ARO 180, PK 047+42 1, PN G047.0+42.4, and Abell 39

Abell 39 is a low surface brightness planetary nebula in the constellation of Hercules. It is the 39^th entry in George Abell's 1966 catalog (and 27^th in his 1955 catalog) of 86 old planetary nebulae which either Abell or Albert George Wilson discovered before August 1955 as part of the National Geographic Society - Palomar Observatory Sky Survey.Harvnb|Abell|1955] Harvnb|Abell|1966] It is estimated to be about 6,800 light-years from earth and 4,600 light-years above the Galactic plane. It is almost perfectly spherical and also one of the largest known spheres with a radius of about 2.5 light-years.Harvnb|Darling|2008]

Central star

Its central star is slightly west of center by about 2″ or 0.1 light-years. This offset does not appear to be due to interaction with the interstellar medium, but instead, it is hypothesized that a small asymmetricmass ejection has accelerated the central star. The mass of the central star is estimated to be about 0.61 M_☉ with the material in the planetary nebula comprising an additional 0.6 M_☉.

This planetary nebula has a nearly uniform spherical shell. However, the eastern limb of the nebula is 50% more luminous than the western limb. Additionally, irregularities in the surface brightness are seen across the face of the shell. The source of the east-west asymmetry is not known but it could be related to the offset of the central star.

Structure and composition

The bright rim of the planetary nebula has an average thickness of about 10″.1 or about 0.34 light-years. There is a faint halo that extends about 18″ beyond the bright rim giving a complete diameter of around 190″ under the assumption that this emission is uniform around the planetary nebula.

This planetary nebula has been expanding for an estimated 22,100±|1700|1500 years, based on an assumed expansion velocity between 32 and 37 km/s and a 0.78 parsec radius.

Background galaxies are visible near the nebula, and some can be seen through the translucent nebula.

Oxygen is only about half as abundant in the nebula as it is in our own sun.

Notes

References

* citation
last1 = Abell
first1 = George O.
authorlink = George Ogden Abell
title = Globular Clusters and Planetary Nebulae Discovered on the National Geographic Society-Palomar Observatory Sky Survey
journal = Publications of the Astronomical Society of the Pacific
year = 1955
volume = 67
issue = 397
pages = 258
url = http://adsabs.harvard.edu/cgi-bin/bib_query?1955PASP...67..258A
doi = 10.1086/126815
* citation
last1 = Abell
first1 = George O.
authorlink1 = George Ogden Abell
title = Properties of Some Old Planetary Nebulae
journal = Astrophysical Journal
year = 1966
date = April 1966
volume = 144
issue =
pages = 259
url = http://adsabs.harvard.edu/abs/1966ApJ...144..259A
* citation
last1 = APOD
authorlink1 = Astronomy Picture of the Day
editors = Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
title = Abell 39
year = 2005
date = July 28 2005
url = http://apod.nasa.gov/apod/ap050728.html
* citation
last1 = Darling
first1 = David
authorlink = David Darling (astronomer)
journal = Internet Encyclopedia of Science
title = Abell 39
year = 2008
url = http://www.daviddarling.info/encyclopedia/A/Abell_39.html
* citation
last1 = Jacoby
first1 = George. H.
last2 = Ferland
first2 = Gary. J.
last3 = Korista
first3 = Kirk T.
authorlink =
journal = The Astrophysical Journal
volume = 560
issue = 1
pages = 272–286
title = The Planetary Nebula A39: An Observational Benchmark for Numerical Modeling of Photoionized Plasmas
year = 2001
date = October 10 2001
doi = 10.1086/322489
url = http://adsabs.harvard.edu/abs/2001ApJ...560..272J
* citation
last1 = SIMBAD
title = Results for PN A66 39
authorlink = SIMBAD
journal =
year = 2008
date = September 5 2008
publisher = SIMBAD, Centre de Données Astronomiques de Strasbourg
url = http://simbad.u-strasbg.fr/simbad/sim-id?Ident=PN+A66+39

External links

* [http://www.noao.edu/image_gallery/html/im0636.html George Jacoby et al. created a spectacular image of Abell 39 in 1997.]