Abell 78 resides approximately 5,000 light-years away in the constellation of Cygnus. Also known as ACO 78, PK 081-14.1 and ARO 174, this planetary nebula is 2.8 light-years across. Abell 78’s faint halo consists mostly of hydrogen, and its inner elliptical ring is made of helium.
Hubble astronomers said, after exhausting the nuclear fuel in their cores, stars with a mass of around 0.8 to 8 times the mass of our Sun collapse to form dense and hot white dwarf stars. As this process occurs, the dying star will throw off its outer layers of material, forming an elaborate cloud of gas and dust known as a planetary nebula. This phenomenon is not uncommon, and planetary nebulae are a popular focus for astrophotographers because of their often beautiful and complex shapes. However, a few like Abell 78 are the result of a so-called born again star. Although the core of the star has stopped burning hydrogen and helium, a thermonuclear runaway at its surface ejects material at high speeds. These ejecta shock and sweep up the material of the old nebula, producing the filaments and irregular shell around the central star seen in this picture.
The new color image of Abell 78 is a composite of separate exposures acquired by Hubble’s Wide Field Camera 3 (WFC3) instrument and the 1.4 Gigapixel camera (GPC1) on the 1.8-m Pan-STARRS1 (PS1) telescope. Four filters were used to sample various optical wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter.
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