Astronomers remain fascinated by gamma-ray bursts. These bursts of energy appear to be among the most powerful explosions in the universe today. They occur about once a day and are divided into two categories. The first category is called long gamma-ray bursts and last from two seconds to about thirty seconds. They have a clearly defined burst of energy followed by an afterglow which can be clearly seen. The second type is short gamma-ray bursts. These bursts last under two seconds and most last a few milliseconds.
When gamma-ray bursts were first detected in 1969, scientists believed the intense flashes of energy may have originated from distant alien civilizations. We now know that gamma-ray bursts result from the cores of massive stars collapsing at the end of their lives. These stars are known as supernovas and, if the star has enough mass, they turn into black holes. As the gas descends into the center of the black hole, some of it escapes as gamma-rays and is shot out from the dying star’s poles at nearly the speed of light.
Although gamma-ray bursts only last from a few seconds to a few minutes and are not visible to human eyes, they emit the same amount of energy the Milky Way produces in 100 years and are brighter than all other sources of gamma-rays, including neighboring stars and our Sun. Scientist have observed gamma-ray bursts from 13.14 billion light-years away, making them the most powerful forms of energy in the universe, secondary only to the big bang.
Gamma-ray bursts produce large amounts of gas that evelopes the entire surrounding area. Because new stars form from the gas clouds left behind by larger stars that have undergone the supernova process, gamma ray bursts are often found in these “stellar nurseries.” Scientists now use gamma-ray bursts to locate areas of new star formation and study the life cycle of stars.
Astronomers also believe that long gamma-ray bursts are caused by the collapse of a Wolf-Rayet star. When the star collapses, a black hole is formed within the star. Then, as the star further collapses, matter escapes from the star. It is this matter that astronomers are seeing.
These long gamma-ray bursts come from all directions within the universe. Astronomers believe that most of them originate at the very edge of where the most powerful telescopes can see and beyond. NASA and other space agencies have satellites that are studying the bursts. When they detect one, they send a signal to several points on Earth. Telescopes can then be pointed in the right direction.
Image Credit: 1) Artist’s conception of a gamma-ray burst by NASA/SkyWorks Digital
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