New Type of Stellar Death Possibly Identified

When massive stars several times heavier than our Sun reach the end of their burning cycle, their life ends in violent explosions known as supernovae. When this happens, massive amounts of energy and radiation are produced, creating light signatures that briefly outshine entire galaxies. Thus far, astrophysicists believed that there were only two types of supernova explosions, but it would now appear that a third one may also exist. The idea, suggested in the latest issue of the esteemed scientific journal Nature, was derived from observations of two odd-looking supernovae, Space reports.

The first kind of established supernova explosion is called a core-collapse, and it usually takes place in stars that are at least 8 times heavier than the Sun. Towards the end of their lives, these giant fireballs violently eject the outer layers of their atmospheres, while at the same time their core collapses in on itself. The second type of explosion takes place when stellar remnants known as white dwarfs begin to accumulate mass, and continue to do so until finally they become unstable. When this happens, they also explode in supernova explosions, experts say.

However, researchers at the Harvard University Center for Astrophysics (CfA) say that they have observed two instances in which the violent explosions did not fit any of the two patterns. The object SN 2005E, for example, is really faint, and its light signature is quickly fading away. Still, it exhibits some of the traits associated with core-collapse supernovae. For instance, it lacks elements such as hydrogen and silicon. Usually, massive stars collapse because they can no longer sustain nuclear fusion. This happens due to the fact that they exhaust their hydrogen gas supplies. The thing about this object is that it lies in the galaxy NGC 1032, which no longer produces stars. The massive variety does not readily occur in such galaxies.

“We didn't find any trace of star formation. That's the basic strange thing about this supernova,” CfA expert Hagai Perets, also a study researcher, said of the study. The second interesting object is the supernova SN 2005cz, which is rich in calcium, and also very faint. Generally, massive stars do not have a significant calcium signature, which puzzles investigators further. The body is found in the elliptical galaxy NGC 4589, and this is weird because such galaxies generally do not support the formation of very massive stars. SN 2005cz would only make sense if it appeared after the explosion of a star 10 to 12 times more massive than the Sun.