In 1967 scientists first noticed random flashes in the sky and began studying them. It wasn’t until 1971 that scientists identified the flashes as gamma-ray bursts, explosions of tight jets of energy, thousands of times brighter than a supernova. Since that time, based on observations, scientists have linked these bursts to the death of stars.

In this activity you will explore the three different aspects of the death of a star: energy, duration, and variability -- to determine if the star is a source of gamma ray bursts. For additional information please refer to the background essay in the Gamma Ray Burst Detectives (Elementary School) .

Energy:

The energies involved with the Sun, other kinds of stars, and gamma-ray bursts are much, much larger than any event that happens on Earth. The energy of a car traveling at freeway speed is about 10,000,000,000,000 ergs. A magnitude 7.0 earthquake releases 20,000,000,000,000,000,000,000 ergs, the equivalent of 2 billion freeway-speed cars or 2000 strong tornadoes. By comparison, the energy released in a gamma-ray burst is about: 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 ergs.

There isn’t any name for a number this big, and since it’s hard to write numbers like that out, scientists use a mathematical shorthand instead. An object that can generate 1051 ergs of total energy is a good candidate to produce a gamma-ray burst.

Duration:

Besides finding an object that can generate 1051 ergs of energy, you also need to find one that can emit that energy quickly. We’re interested in gamma-ray bursts that last for a few seconds to a few minutes, so this is the duration we’re looking for.

A gamma-ray burst must generate 1051 ergs of total energy within a period of time lasting between a second and a few minutes.

Variability:

The third important property that can help you figure out if an object could create a gamma-ray burst is how quickly the object’s emission is varying.

Not only do gamma-ray bursts give off a huge amount of energy in a short time, but the emission of the gamma-ray burst can increase by a large amount, or drop down close to zero, within a short amount of time, seconds or less.

Gamma-ray burst emission varies dramatically over time spans of a second or less. What does it mean to have varying emission? Well, if you think about an ordinary light bulb, that light bulb will give off the same amount of energy every second for its whole working life. Contrast that to the twinkling lights from a Christmas tree – these bulbs are wired to get brighter and dimmer every second or so. In this sense, we can say that their emission varies significantly over that time span.

To learn more about the search for gamma ray bursts, check out more about NASA’s Swift mission at Swift: Gamma-Ray Bursts.

To explore possible theories explaining the origin of gamma ray bursts, check out how scientists have learned about gamma ray bursts using data gathered by the Swift satellite at Gamma-ray Burst Theories.

To learn more about the history of the study of the stars, check out the geocentric and heliocentric models and, how culture influences the interpretation of scientific data at Universe Origins.

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