The first sighting of gamma-ray bursts (GRBs) occurred in 1967 by military satellites. GRBs last mere seconds yet give off more radiation energy in their few seconds than our sun radiates throughout its entire lifetime. Scientists have long debated the origins of gamma-ray bursts. At the time of Swift's launch, two theories had merit. One theory was that the bursts occur when two neutron stars merge. The other theory was that the bursts are the result of a massive star collapsing.
Thousands of years ago, science and the study of the stars were in their infancy. Aristotle hypothesized that the earth was the center of the universe. The Sun and the five known planets were believed to move in uniform circular motion around the Earth. This is called the geocentric model. It plausibly explained the motions of the celestial bodies in our sky and was the accepted model for many hundreds of years.
Copernicus, though, examined the evidence and developed another theory. He hypothesized that it is the Sun and not the Earth that is the center of the Solar System. He expected his theory would be controversial so he waited to published his work upon his death.
Kepler improved upon Copernicus’ theory by replacing the uniform circular motion of the planets with elliptical orbits. His work allowed Copernicus’ model to fit the scientific and mathematical data available to astronomers.
This struggle to understand the nature of objects’motions in our sky is an excellent historical example of how scientists struggle to explain all new mysteries, like the nature of GRBs. What is known about GRBs is that they occur throughout the universe, two to three times a day, at random places in our sky. GRBs can be in one of two categories: Short – lasting 2 seconds or less, or Long – lasting up to 90 seconds. The two types differ in more ways than their duration. Short bursts produce more high-energy gamma rays than their longer counterparts do.
Swift is a satellite designed by Penn State researchers and launched by NASA to study gamma-ray bursts. Catching a GRB is no easy task. The burst can appear from any direction without warning and can last for a few milliseconds to just over a minute. The satellite has to move quickly and be in position to capture the data. Swift searches and records GRBs and other phenomena it observes in the sky.
Using Swift’s data, astronomers have come to understand GRBs much more deeply than we did in 2005. Using data from the Swift satellite we now believe that both models are correct: some GRBs are caused by collapsing stars and others by merging neutron stars.