The Hubble 5 Planetary Nebula
The Hubble Double Bubble Planetary Nebula is bubbling over with excitement. More mundanely known as Hubble 5 , this bipolar planetary nebula is being created by a hot wind of particles streaming away from the central star system. The hot gas expands into the surrounding interstellar medium in a fashion similar to the inflation of hot air balloons . A supersonic shock-wave can form at the boundary, causing newly excited gas there to shine as electrons recombine with resident elements . In the above picture , colors are assigned according to the energy of the recombinant radiation. This star system lies about 2200 light-years from Earth , and likely includes a Sun-like star slowly transforming itself into a white dwarf .