Planetary nebula Abell 78 captured by Hubble Space Telescopes’ wide-field camera 3 and PANSTARSS. Credit: ESA / Hubble & NASA, M. Guerrero, Recognition: Judy Schmidt
Abell 78 is about 5000 light-years away in the constellation Cygnus (The Swan) and is an unusual type of planetary nebula.
After the nuclear fuel in their core is depleted, stars with a mass of about 0.8 to 8 times the mass of our sun collapse to form dense and warm white dwarf stars. As this process takes place, the dying star will discard its outer layers of matter and form an extensive 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. Some like Abell 78, however, are the result of a so-called “born again” star.
Although the star’s core no longer burns hydrogen and helium, a thermonuclear scavenger ejects material at its surface at high speeds. This ejection shocks and wipes the material from the old nebula, yielding the filaments and irregular shell around the central star, as seen in this Photo of the Week, which contains data from Hubble’s Wide Field Camera 3 and PANSTARSS.