Planetary Nebula MWP 1

This nebula has first been noticed in 1987 by Alain Maury on a blue plate taken with the 48 inch Palomar Schmidt telescope. In 1992 Motch, Werner and Pakull (MWP) identified the ROSAT X-ray source RX J2117.1+3412 with a PG 1159 star. In the same year Appleton, Kawaler and Eitter discovered a huge planetary nebula surrounding this X-ray source.

MWP 1 is a planetary nebula with a bipolar structure in its central part and faint linear filaments, suggestive of shocks, in its outer regions. It has a maximum extent of 13 arcmin. Distance measurements from Gaia EDR3 are given with 502 pc, this gives a size of approximately 1.9 pc. The expansion age of the nebula suggests an age of approximately 150'000 years, which is much older than its central star, which is a PG 1159 spectral class star. These stars are hydrogen-deficient pre-white dwarfs representing the hottest stage of post-AGB stellar evolution. These objects are believed to be on the evolutionary path from the Wolf-Rayet central stars of planetary nebulae (spectral type [WC]) and the hottest He-rich white dwarfs (spectral type DO). This star shows a spectrum of a surface temperature of around 150'000 K. ^{[719, 720]}

Planetary Nebula Alv 1

This planetary nebula Alv 1 (PN G079.8-10.2) was serendipitously discovered by Portugese amateur astronomer Filipe Alves in November 2009. He was photographing MWP 1 using an 8-inch ASA astrograph F/3.7 FLI Microline, with a wide field of 60x80 arcminutes and exposure time 14.1 hours with Hα filter plus 8.6 hours O-III filter. Later optical observations were performed remotely at the CROW observatory in Portalegre, Portugal. They revealed a very blue star of ~18.2 mag, approximately 12" away from the geometrical centre of the nebula, which possibly could be the central star. ^[509]