Stars and the gases between them emit heat and light in all directions into space through electromagnetic waves. By collecting the radiation, astronomers learn about the age, composition, and size of the universe beyond our solar system.

Within the universe groups of stars, dust and gases held together with gravity are galaxies. The size and shape of galaxies vary, along with the ages of their stars. Galaxies’ shapes are spiral (with arms), elliptical (without arms) or irregular. Earth and its solar system sit in a large, spiral galaxy, the Milky Way, about two-thirds of the way out from the center.

The Milky Way Galaxy is about 100, 000 light-years wide with a nucleus that is 10,000 light-years thick. Light-years are the distance light travels in a year, about 6 trillion miles or 10 trillion kilometers.

Stars are born in nebulae, or dark, cool clouds of dust and gases found between other stars. It is not known why, but sometimes nebulae grow dense enough to contract, pulling their particles toward the center. At the protostar stage a developing star converts gravitational energy to heat energy increasing its core temperature. Over a million years the core becomes hot enough for nuclear fusion of hydrogen, and a star is born. The star’s gravity and external pressure stabilize during the main-sequence stage where it remains for most of its life. When a star runs out of nuclear fuel and dies, it leaves behind a remnant: a white dwarf, a neutron star or a black hole.

Changes in the life of a star can be subtle or explosive. The death of a massive star results in a brilliant explosion called a supernova. Three have been observed in our galaxy, including one recorded by the Chinese in 1054, which left a stellar remnant, the Crab Nebula.

NASA’s SWIFT satellite detects the biggest, most mysterious explosions in the cosmos, gamma ray bursts. Once detected, the satellite points its Ultraviolet/Optical and X-ray telescopes at the gamma ray burst and documents the amount of energy released, how long the burst lasts, and how fast light from the burst rises and falls.

On April 23, 2009, SWIFT tracked a gamma ray burst that broke the record for most distant object in the universe. Astronomers estimated it was from the explosion of a massive star about 13 billion light years away representing a relic from when the universe was very young, only 630 million years old.

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.

Print Background Essay