The Universe’s Biggest Explosions

Everyday, there are a few explosions ripping through distant galaxies that produce enough energy in a few seconds to power the Sun for its entire lifetime. Or in more terrestrial terms, these explosions are as powerful as 10,000,000,000,000,000,000,000,000,000,000,000,000 100 watt lightbulbs. Yet, no one knew about them until the 60s. Even then, they weren’t detected by astronomers, but by U.S. satellites designed to sniff out Soviet nuclear testing. It wasn’t until the late 90’s that they were studied in large numbers. Now, with data coming from the Swift satellite, astronomers have started to more fully understand what may be causing these large explosions.

These explosions are called Gamma ray bursts, or GRBs for short. They contain gamma rays, which are high energy photons, much more powerful than a typical x-ray. Gamma ray bursts are fairly rare, which is good news for us here on Earth. There have been suggestions that if a GRB were to go off in our Galaxy, there would be mass extinctions or mutations. All of the GRBs that have been detected to date are much further away, like the one shown in the movie above. This was one of the largest GRBs ever detected and was visible to the naked eye for a short amount of time…not bad for an object billions of light years away from us!

In 2004, astronomers launched the Swift satellite, which contains a variety of instruments for studying these explosions. The main advantage of using Swift is that it really is fast. Once a burst is detected, the satellite can lock onto the target within a few minutes. This process used to take days in the past. Once a burst is detected, its brightness is monitored for a period of days to hours. Changes in this brightness with time, called a lightcurve, can help astronomers model the explosion mechanism behind the bursts.

Using data from the Swift satellite, Maria Giovanna Dainotti, Michal Ostrowski and Richard Willingale show that bursts actually fall into a variety of categories. Their paper, titled Toward a standard Gamma Ray Burst: tight correlations between the prompt and the afterglow plateau phase emission, shows that certain lightcurve features are correlated. But this is only the case for some, not all, GRBs. What this suggests is that there may be slight differences in the progenitors of these explosions, and that astronomers should be sure they are only comparing apples to apples. However, being able to classify these tremendous explosions is the first step in understanding how they are formed.