EIU Astro

Gamma Ray Bursts by Danielle Thompson July 24, 2012

In an extremely distance galaxy far far away, billions of light years away from Earth, something remarkable happens nearly every day. The brightest and most energetic events known to the universe perform an electromagnetic lightshow. This extravagant phenomenon releases as much energy in a few seconds as the Sun does in its entire lifetime. This amazing occurrence is thought to be connected to the explosive death of a massive star or the collision of neutron stars. These spectacular incidents, known as gamma ray bursts, that only occur on average for 20-40 seconds produce sudden intense flashes of gamma radiation that outshines everything else in the sky.

Gamma Ray Burst

The discovery of the first gamma ray burst was a fortunate derivative of nuclear war defense using U.S. Vela satellites in the late 60’s. The US military satellites were carrying gamma ray detectors because nuclear reactions from bomb tests would give off gamma radiation. The satellites detected a flash of gamma radiation uncharacteristic of any nuclear weaponry. Surprisingly, this discovery was not of urgent concern to the US and over the next ten years with improved technology more information was collected and finally published in a scientific journal.

A later version of an Italian-Dutch satellite, BeppoSAX, launched in 1996 was equipped with not only a gamma ray but an x-ray detector allowing for the observation of the first “afterglow” of a gamma ray burst. An afterglow is caused from the burst colliding with the interstellar gases emitting longer wavelengths. Today NASA satellites are used to create the Gamma-ray Burst Coordinates Network (GCN) which coordinates space and ground-based observations to allow for better viewing of gamma ray bursts’ afterglows.

NASA

Further investigation into gamma ray bursts due to the improvements of satellites has allowed for the classification of long and short duration bursts. Long bursts have to last for more than 2 seconds and astronomers are fairly certain the cause of long duration gamma ray bursts is a rapidly rotating massive star, greater than 100 solar masses, and known as a supernova that is collapsing to form a black hole. Short duration bursts make up 30% of all bursts and are thought to be caused by neutron stars colliding. While studying long and short duration bursts, it has been discovered that no two bursts have the same light curve, this is a mystery that still plaques astronomers today.

Light Curves

A new possible explanation for gamma ray burst is a hypernova. Scientists refer to a hypernova as a “failed supernova”, which is still a massive star whose core has collapsed but didn’t go boom. The hypernova’s shock wave doesn’t blow off the outer layers like a supernova does. The outer layers fall into the central neutron star or black hole and produces enormous amount of heat and radiation with an outcome of higher luminosity than a supernova. A hypernova has become the favored possible explanation because gamma ray bursts are more luminous than a supernova. The actually existence of hypernovae is still a hot debate.

Some astronomers suffer from ergophobia, the fear of energy, and the fear that our galaxy the Milky Way could experience a bad day. The scenario of a gamma ray burst firing its extremely energetic radiation at planet Earth is dishearting. The intense gamma rays would be stopped by the Earth’s stratosphere but the ozone layer would be destroyed. Would the depletion of the ozone layer inevitable cause a mass extinction? Gamma ray bursts fuel the speculation that there is a conceivable end to life as we know it on Earth.

The Milky Way

LIVE UPDATE OF GAMMA RAY BURSTS AND THEIR AFTERGLOWS