Work experience student Shohana on Gamma Ray Bursts

Work experience student Shohana on Gamma Ray Bursts

Published by Geoff Wyatt on May 7, 2009 No Comments

Sydney Observatory regularly hosts work experience students from Year 10 each year. They are given the opportunity to stay for a week and learn to “drive” our telescopes, assist with tours and research some simple topical ideas.

This week Shohana has decided to discuss Gamma Ray Bursts as an amazing observation was made just two weeks ago which has set a new distance record for the observable Universe.

Gamma rays are the most energetic form of light. Gamma Ray Bursts (GRB) are extra galactic short-lived, intense sources of gamma ray photons.

They are thought to be caused by the supernova explosion of a super massive star (at least 30 times more massive than the Sun) at the end of its life. As the core of the star runs out of nuclear fuel it collapses, explodes and if massive enough, may form a black hole. The blast wave from the collapse collides with the outer layers of the star and produces vast amounts of Gamma ray photons which then escape just ahead of the blast itself now travelling at close to the speed of light.

Gamma ray bursts occur in distant galaxies and are usually an enormous distant away from Earth which is measured in light years. On average one is seen per day.

GRBs are detected by satellites orbiting Earth, in particular by Beppo SAX until 2002 and more recently NASA’s Swift. A GRB is brighter than a normal supernova and billions times brighter than the Sun. Therefore, a GRB is the brightest source of cosmic gamma ray photons in the universe.

On 23rd April 2009, NASA’s satellite, Swift, and a team of astronomers detected a GRB from a star which occurred when the universe was 630 million years old. It is known as the most distant and cosmic explosion ever seen since the Big Bang. The distance was recorded to be approximately of 13 billion light years which is the most distant object ever seen so far, albeit in Gamma rays and the infra red!

grb090423_sm
This image merges data from Swift’s Ultraviolet/Optical (blue, green) and X-Ray (orange, red) telescopes. No visible light accompanied the burst, which hints at great distance. The image is 6.3 arcminutes wide.

Image Credit: NASA/Swift/Stefan Immler

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