PN Abell 39

Planetary Nebula Abell 39 is a rather large bubble in western Hercules. It is one of the most symmetrical planetary bubbles known. I found several papers defining its distance but they are in wide disagreement.

1700 light-years: http://mnras.oxfordjournals.org/content/357/2/619
6000 light-years: http://mnras.oxfordjournals.org/content/353/2/589
6850 light-years: http://iopscience.iop.org/0004-637X/560/1/272/

Wikipedia says 6800, APOD says 7000. I suppose it is safe to say the 1700 figure is likely very wrong. Using 6800 light-years I get a size of 5.6 light-years which seems large to me for such a bright planetary. Usually they are very faint at this size.

The central star is quite bright and not in the center but about 2" off center. Usually this means the motion of the nebula through the interstellar medium has caused the nebula to lag behind the central star. The brightest edge usually denotes a planetary's leading_edge. If so then the star is displaced toward the trailing edge not the leading_edge. It appears that in the off centered star may be due to velocity differences at the nebula's creation and the nebula is not showing motion through the interstellar medium at all. This is an oddity that needs more study.

Being in a part of the sky with little dust and gas a lot of background galaxies are visible in the image. I've annotated all with redshift values at NED. I surprising number have a distance of about 1.69 billion light-years, including the three seen through the nebula itself. Yet I found no listing for a galaxy group at that distance in my image or within 40 minutes of its center. One of the three in the nebula is a ULIRG which stands for Ultra Luminous Infra Red Galaxy. It's IR status was discovered by IRAS. The first IR space telescope that cataloged IR sources in the sky.

14" LX200R @ f/10, L=4x10' RGB=2x10' STL-11000XM, Paramount ME

Rick

Beautiful image Rick. The PN is nicely accompanied by lots of small
galaxies, some of which even show good detail in your image.

Stefan

"WA0CKY" schrieb im Newsbeitrag ...


Planetary Nebula Abell 39 is a rather large bubble in western Hercules.
It is one of the most symmetrical planetary bubbles known. I found
several papers defining its distance but they are in wide disagreement.

1700 light-years: http://mnras.oxfordjournals.org/content/357/2/619
6000 light-years: http://mnras.oxfordjournals.org/content/353/2/589
6850 light-years: http://iopscience.iop.org/0004-637X/560/1/272/

Wikipedia says 6800, APOD says 7000. I suppose it is safe to say the
1700 figure is likely very wrong. Using 6800 light-years I get a size
of 5.6 light-years which seems large to me for such a bright planetary.
Usually they are very faint at this size.

The central star is quite bright and not in the center but about 2" off
center. Usually this means the motion of the nebula through the
interstellar medium has caused the nebula to lag behind the central
star. The brightest edge usually denotes a planetary's leading_edge.
If so then the star is displaced toward the trailing edge not the
leading_edge. It appears that in the off centered star may be due to
velocity differences at the nebula's creation and the nebula is not
showing motion through the interstellar medium at all. This is an
oddity that needs more study.

Being in a part of the sky with little dust and gas a lot of background
galaxies are visible in the image. I've annotated all with redshift
values at NED. I surprising number have a distance of about 1.69
billion light-years, including the three seen through the nebula itself.
Yet I found no listing for a galaxy group at that distance in my image
or within 40 minutes of its center. One of the three in the nebula is a
ULIRG which stands for Ultra Luminous Infra Red Galaxy. It's IR status
was discovered by IRAS. The first IR space telescope that cataloged IR
sources in the sky.

14" LX200R @ f/10, L=4x10' RGB=2x10' STL-11000XM, Paramount ME

Rick


--
WA0CKY