This large but very faint planetary nebula is located 1700 light years away in the constellation of Monoceros at a declination of -6 degrees. Also known as G222.1+3.9, it spans 19 arc-minutes in our apparent view. This corresponds to a diameter of 10 light years, huge for a PN and indicative of an old (ancient) nebula. Its age is believed to be about 70,000 years.
The discovery of this PN was announced in the 2004 paper, PFP 1: A Large Planetary Nebula Caught in the First Stages, by Pierce, Frew, Parker and Koppen. It is not clear to me how Dr. Koppen could get his name on the paper but not on the nebula.
This one of the few PN which forms an
absolutely perfect circle, except for the HII rim signal at the 1 o’clock position. The paper states that this HII rim signal is due either to movement of the PN with respect to its surroundings or an encounter with a region of higher density as the PN expands.
At the center of this circle is the magnitude 15 progenitor star. In the full resolution view, it seen as the faint tiny darker-blue star, unique in the frame, that is typical in color of most progenitor stars I have imaged.
This is the second image of this object on Astrobin.
Comments