She fascinated us with her explanation of gamma-ray bursts (or GRBs as they are otherwise known), and their extraordinarily high energies, which are higher than nuclear bombs and the Sun combined. In fact, they will emit more energy in 10 seconds than the Sun will release in its entire lifetime! GRBs are extremely energetic explosions that take place in galaxies when a supernova occurs as a star collapses in on itself and produces a black hole – although this is just a prediction as to what is thought to cause them. There are many different types of GRBs; long, short, hard and soft. They were actually first discovered entirely by accident when U.S. military satellites were searching for Soviet nuclear testing in the late 1960s. The satellites were on the lookout for gamma rays, because nuclear explosions produce gamma rays. This resulted in the satellites finding multiple bursts of gamma rays that seemed to be further out from the solar system.
Dr. Schady told us about how physicists are attempting to capture the ‘afterglow’ of these bursts in order to find out more information about them. The afterglow consists of high-energy gamma rays, X-rays, visible light and radio waves. It is much easier to find out this information for the Long GRBs as they last for longer, so we have a much higher chance of detecting the energy left behind since it will take much longer to dissipate. On the other hand, there have only been a very small number of detections made of the energy left behind after a short GRB, since by the time we have located where to look to detect the energy it will have already disappeared.
Dr. Schady showed us a pictorial representation (BATSE map) of the 2704 GRBs detected from 1991 up to 2000. The colours in the picture represented the intensity of the energy of the bursts. She told us that what was interesting about the picture was the fact that the bursts are scattered about evenly, rather than confined in a specific shape or pattern. She told us that it showed astronomers that the GRB’s must originate from outside our own galaxy.
Dr. Schady spoke about a NASA telescope named ‘The Neil Gehrels Swift Observatory’ that was launched into space in November 2004 to detect GRBs. Swift is unique in that it can swivel round, it has a much larger yet more basic detector on one side which will just look out for any sign of a GRB. If one is found, it will swivel round to collect information with its more precise detectors. It will also send the location of the GRB back to astronomers on Earth (Dr. Schady gets a mobile phone alert every time this happens!) so that they can use their high tech telescopes to try and find the afterglow. Swift has X-ray and visible telescopes, which are used to gather information about the bursts.
To end the talk, Dr, Schady spoke about what the future holds for GRBs and how important ‘multi-messenger’ astronomy (the combination of gravitational waves and light) will be, and how she is planning on continuing with her research into short GRB’s.
[Image credit http://www.mpg.de and NASA]