Israeli scientists, working with their counterparts in the US, Germany, and elsewhere, have discovered what appears to be a third type of supernova. The group published its findings this week in the journal Nature.

Dr. Avishai Gal-Yam and Hagai Peretz of the Weizmann Institute (Peretz now works at the Harvard-Smithsonian Center for Astrophysics) were part of the team that began investigating a strange astronomical phenomenon in early 2005. The team began following what appeared to be a normal supernova, only to discover that its explosion pattern did not fit either of the two patterns previously seen.

The two known types of supernova were the violent explosions of hot, young gas giants, and the thermonuclear blasts given off by old, dense stars known as white dwarves.

The supernova tracked by Gal-Yam, Peretz and others did not match the blast of a white dwarf in terms of chemical makeup. However, it gave off little material compared to an exploding gas giant, and its location indicated that it was not a young star.

The exploding star ejected unusually high quantities of calcium and titanium, indicating that the nuclear reaction involved helium. Gal-Yam explained that the reaction may have involved two stars, both white dwarves, one of which “stole” helium from the other.

“The donor star is probably completely destroyed in the process, but we’re not quite sure about the fate of the thief star,” he said.

Scientists believe previously observed supernovae may fit the new, third supernova pattern. If the theory of a third supernova type is correct, it could help understand currently unexplained phenomena such as the prevalence of calcium in the universe.