The first star explosions were gigantic – and asymmetrical
After a star with significantly more mass than the Sun has consumed all its fuel, it decays into a massive firework display, a supernova. In today’s universe, that is not a very common sight, because the greatest percentage of stars is made up of red dwarfs, which end their lives not nearly so spectacularly. Our Sun is also not destined to turn into a supernova. It will grow into a red giant and then, at the end, only a harmless white dwarf will remain.
In the early universe, however, things were much different. At that time, there were neither red dwarfs nor stars around the size of our Sun. Instead, the much smaller universe at that time was filled with giant stars that today would be classified in so-called Population III. They were made only of what the big bang had supplied for them: hydrogen, helium, and a bit of lithium. But the composition of the cosmos changed as these early stars ended their short, but energetic lives. Their explosions created the first heavy elements that would accumulate to form stars of the younger Populations II and I.
Previously, researchers assumed that supernovae during the early universe were no different than today’s explosions. In today’s universe, stars explode in all spatial directions simultaneously, as would be expected. Thus, the explosion’s wave front is a sphere. But a research team from MIT noticed something strange from the star HE 1327–2326: it contains an unexpectedly large amount of zinc. The star HE 1327–2326, which is only 5,000 light-years from Earth, contains so few heavy elements that it clearly belongs in Population II, which contains stars created directly after the first stars. Thus, it was born from the material ejected from the first supernovae.
There’s just one problem, however. The relatively high percentage of zinc cannot be explained with a normal supernova. Normal supernovae would simply not produce enough zinc. The MIT researchers thus ran simulations of supernova explosions in computers. The surprising result: enough zinc is produced only if the progression of the explosions is not symmetrical. Instead, the explosions must have developed jets directed in opposite directions (see the picture below), in which zinc was then created. Such a supernova must have been five to ten times more energetic than originally assumed. The astronomers have even theorized that most supernovae in the early universe developed in this way. It could also be possible that the much stronger explosions might have more strongly influenced the development of the universe during the reionization era than previously thought.