PFP 1 is a large highly evolved planetary nebula that was discovered in 2004 by Quentin Parker, David Frew and Mark Pierce. It is one of the most well known objects discovered in the SuperCOSMOS H-alpha Survey (SHS) as part of the Macquarie/AAO/Strasbourg Ha Planetary Nebula Catalog (MASH) project. The SHS Ha Survey has been crucial in the discovery of extremely faint planetary nebulae and other types of objects that can only be detected with narrowband imagery due to their intense faintness. The MASH catalogue contains about 1200 planetary nebulae and along with other galactic Ha surveys, it has helped to double the number of known planetary nebulae to approximately 3000. PFP 1 is one of the largest planetary nebulae found with an apparent size of 19 arcminutes. It is characterised by a thin faint almost perfectly annular ring with a brighter limb to the north. This bright rim structure is faintly visible in POSS I and POSS II red plates and it is the result of the planetary nebula starting to interact with the ISM. This part is brighter than the rest of the nebula due to the material in the planetary nebula-ISM boundary being compressed, which leads to a brightness enhancement in the direction of motion of the planetary nebula. Few examples of planetary nebulae with ISM interaction are known due to their extremely low intrinsic brightness. Currently 100 are known and the southern SuperCOSMOS H-alpha Survey along with the INT/WFC Photometric Ha Survey of the Northern Galactic Plane (IPHAS) have been invaluable in the detection of more of these rare examples. This stage in the evolution of a planetary nebula precedes the total dilution and fading of a planetary nebula. However, the phenomenon of ISM interaction has been observed in young planetary nebulae with high speed central stars and studies conclude that different stages of interaction are exhibited throughout the life of planetary nebulae. The idea of a planetary nebula interacting with the ISM as it moves through space was proposed in 1969 by the Armenian astronomer Grigor Gurzadyan. PFP 1 lies in an area of relatively low extinction at a distance of 1800 light years and its size is approximately 10 light years. However, the cause of its interaction with the ISM isn't conclusive. It is either due to the motion of the planetary nebula or an encounter with an area of enhanced density in the local ISM as it expands outwards. In addition to its prominent Ha emission, it also contains weak OIII emission as it is a low excitation object.
Thanks to Sakib Rasool for suggesting me this little known object and for preparing the above object description.
Apo TEC140 (140/f7.2) - FLI Proline 16803 - Ha (645m) R (100m) G (60m) B (70m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia