A star is born in the Milky Way.

A star is born in the Milky Way

Birth is an exciting process, especially when no one has ever seen it happen before.

The developing embryo lies wrapped in clouds of gas and dust 500 light-years away, near the bright star Antares. The mother, the constellation Ophiuchus in the Milky Way galaxy, will endure birth pangs for another 100,000 years before delivering a star about the size of our sun. Anxiously observing the event -- the first one ever seen by humans -- are astronomers from the University of Arizona at Tucson and the University of Missouri at St. Louis, assisted by the 12-meter radio-telescope of the National Radio Astronomy Observatory near Tucson.

First detected in the galactic womb by the Infrared Astronomical Satellite in 1983, the embryo contains about one-fourth the mass of gas sun but lies at the center of a cloud of gas and dust 10 times the size of our solar system. For the first time, astronomers can see that the inner cloud is falling into the star, adding to the embryonic star's size and mass and making it glow 20 times brighter than the sun. Erick Young, a researcher at the University of Arizona, explains: "When [cloud] material falls in, it eventually crashes onto a surface, releasing gravitational energy in the form of photons," the subatomic particles that make up light. The surrounding outer cloud, however, absorbs the light and reemits the energy as infrared and radio radiation.

Astronomers discovered the developing star while looking at radio waves emanating from the cloud in Ophiuchus. Radio waves detected from the inner cloud were slightly shifted away from their expected values, indicating the cloud is collapsing.

Astronomers don't know what mechanisms trigger the collapse of galactic clouds to form stars (SN:8/25/84,p. 125), but they know that this collapse will end in about 100,000 years, when the embryo will have collected most of the matter in the immediate area. The infant star will then emerge from its surrounding clouds, and future astronomers can pass around cigars.

According to astronomer Charles Lada of the University of Arizona, the large, hot infant will begin to cool and contract for 1 million to 2 million years, until its density causes nuclear fusion to replace gravitational pull as the main source of luminous energy. By then a juvenile, the star can look forward to an adult life of about 10 billion years.