The Wide Field Camera 3 of the Hubble Space Telescope and the PANSTARSS system captured a photograph of the unique planetary nebula Abell 78.
Abell 78 is located about 5 thousand light-years from Earth in the constellation Cygnus and is a planetary nebula of an unusual type.
Low and medium mass stars can be reborn in the final stages of their lives. This happens when ionized gas ejected from a star is attracted back to its surface. This creates a shock that briefly reignites thermonuclear fusion. However, this process is very fast. Astronomers have found only a few examples of such stars.
When the stars have run out of their fuel, several things can happen. Those heavier than 1.4 solar masses – the Chandrasekhar limit – will explode into supernovae. But stars of lesser mass, which can no longer create radiation pressure to withstand the force of gravity, avoid such a fate and simply collapse to form white dwarfs. Before they do, however, the stars shed their outer layers as ionized gas, creating planetary nebulae.
At this point, about 15-20% of such stars may experience the process of “born again”. This happens when ionized gas expelled by stellar winds is pulled back by gravity. A shock is created that momentarily restarts thermonuclear fusion and the last flash appears on the surface of the star. In this process, a lot of dust is thrown out, which hides the star from the field of view.