New observations might explain why explosions on three nearby white dwarfs, the cores of dead stars, recently belched out gamma rays (SN: 9/20/14, p. 15). The discovery stumped researchers because no one expected this type of eruption, called a nova, to produce such high-energy light.
Novas are thermonuclear blasts on the surfaces of white dwarfs that have gorged themselves on gas from a companion star. To spit out gamma rays, the blast needs to run into more gas, which is absent around typical novas.
Laura Chomiuk, an astrophysicist at Michigan State University in East Lansing, and colleagues monitored radio waves from one of the three novas last year. As the white dwarf and its companion danced around each other, gas blown out between the stars slowed down while gas leaving their poles sped away, Chomiuk’s team reports October 8 in Nature. Shock waves formed where the high-speed gas ran into the sluggish debris, accelerating charged particles, which produced gamma rays and radio waves.
The researchers suggest that novas might yield gamma rays frequently. Understanding novas could help astronomers learn whether these eruptions are precursors to type 1a supernovas, one of the most powerful types of explosions in the universe.