HFG1, also cataloged as PK 136+05, is a planetary nebula located in the constellation Cassiopeia. This peculiar object stands out due to its fascinating interaction with the interstellar medium, resulting in an intricate and extended structure that captivates astronomers and astrophotographers alike.

HFG1 was first cataloged in 1982 by Heckathorn, Fesen, and Gull (hence the name "HFG"). It surrounds the binary system V664 Cas, consisting of a white dwarf and a companion star. The pair’s movement through space at high velocity creates a spectacular bow shock, leaving behind a faint, elongated tail stretching over 1.5 degrees across the sky. This interaction produces a striking visual effect, with the bright planetary nebula at its center trailing a wispy, comet-like wake of gas and dust.

This celestial marvel is a late-stage planetary nebula, where material ejected during the dying star’s red giant phase is illuminated by the remaining hot core. The faint surrounding structures are best observed through narrowband filters, particularly in H-alpha and OIII, revealing its intricate details and contrasting colors.

HFG 1 is a very old large, low-surface-brightness planetary nebula in Cassiopeia. It surrounds, and was produced by, a binary star system (V664 Cas) that is moving rapidly through our Galaxy. V664 Cas is comprosed of a white dwarf star and a large red giant. The two stars are very close and rotate around their common centre of gravity every 14 hours. The star system is moving towards the lower left of the image. As HFG 1 plows through the interstellar medium, a bluish bowshock is produced; and a red trail of gas is left behind in its wake.
EQUIPMENT USED
Twin APM TMB LZOS 152 refractors
10Micron GM2000 HPS mount
Twin QSI6120 CCD cameras
Astrodon filters
IMAGE CAPTURE
5nm H-Alpha: 33x1800 bin 2x2
3nm OIII: 35x1800 bin 2x2
Luminance: 11x600 bin 1x1
Red: 10x300 bin 1x1
Green: 10x300 bin 1x1
Blue: 10x300 bin 1x1
Total integration: 38.3 hours
Pixel scale: 0.533 arcsec/pixel
Field radius: 0.351 degrees
Capture dates: 15 October - 6 November 2019
Capture location: Fregenal de la Sierra, Spain

Copyright: Peter Goodhew