GAMMA-RAY BURST

By: Courtney Lee & Kristel Curameng

WHAT ARE GAMMA-RAY BURSTS?

Short-lived bursts of gamma-ray photons.

Gamma-ray photons are the most energetic form of light.

Some are associated with special types of supernovae.

Supertnovae are explosions marking the deaths of massive stars.

FACTS ABOUT GAMMA-RAY BURSTS Lasts anywhere from a few

milliseconds to several minutes.

Shines hundreds of times brighter than a typical supernova.

Shines about a million trillion times as bright as the Sun.

Gamma-Ray Bursts are briefly the brightest source of cosmic gamma-ray photons in the observable universe.

FACTS About once a day,

the sky is lit up by a brilliant flash of energy.

It comes from random directions, different every time.

Brightest objects in the sky.

Human eyes cannot detect Gamma-ray bursts.

FACTS The closest Gamma-ray burst known to date is

over a hundred million light-years away. Most of them come from billions of light years. They outshine our closest stars in our sky from

distances that are billions of times further away. Stupendous amounts of energy are required.

DISCOVERY Discovered in the late 1960s by U.S.

military satellites. The satellites carried gamma-ray

detectors since a nuclear explosion produces gamma rays.

MYSTERY OF GAMMA-RAY BURSTS Gamma-ray bursts used to be the

biggest mystery in high-energy astronomy.

In the early 1900s, astronomers didn’t know if they originated at the edge of our solar system, in our Milky Way Galaxy, or far away near the edge of the observable universe.

Today, satellite observations, follow-up ground-based observations, and theoretical work have allowed astronomers to link Gamma-Ray Bursts to supernovae in distant galaxies.

WHERE DO THEY COME FROM? Most Gamma-ray bursts come from

other galaxies. Often from among the most distant

galaxies in the known universe.

WHAT MAKES A GAMMA-RAY BURST? No one knows for sure Our best theory is based upon several

observed facts: The only way to generate huge quantities

is via gravitational collapse, and black holes can be very efficient at turning this energy into explosive power.

Some of the closest GRBs appear to occur simultaneously with supernovae

Almost all GRBs happen in galaxies containing large numbers of very massive stars.

Short Gamma-ray bursts a duration of less than about two seconds Are more rare, and astronomers were never

able to detect an afterglow of a burst until recently.

The blast of energy only lasts for a few microseconds and then it’s gone.

shorter bursts have no detected afterglow in X-rays or visible light.

short GRBs may happen when two objects called neutron stars merge together, to form an even more bizarre object, a black hole. Or perhaps, some thought, a previously-formed black hole swallowed a neutron-star companion.

Long Gamma-ray burst have a duration of greater than two seconds They are vast majority of explosions caused by

a core-collapse supernova. This is when a star many times larger than our

own Sun runs out of fuel and then collapses inward to form a black hole. This also releases a massive outburst of energy that shines clear across the Universe.

Almost every well-studied long gamma-ray burst has been associated with a rapidly star-forming galaxy and in many cases a core-collapse supernova

WORKS CITED "Gamma-ray Bursts: Introduction to a

Mystery." Imagine The Universe! Home Page. Web. 18 Apr. 2011. <http://imagine.gsfc.nasa.gov/docs/science/know_l1/bursts.html>.

"Gamma-Ray Bursts." UC Berkeley Astronomy Department Home. Web. 18 Apr. 2011. <http://astro.berkeley.edu/research/grbs/grbinfo.html>.

"Gamma Ray Burst." Universe Today. Web. 18 Apr. 2011. <http://www.universetoday.com/73564/gamma-ray-burst/>.