New star forming from interstellar cloud.

In 1,000,000 years or so, a new star will over the Earth in the general direction of the constellation sagittarius, predicts an international team of astrophysicists. "We've believed for a long time that stars form clouds in interstellar space when gravity causes the clouds to collapse," explains Neal Evans of The University of Texas at Austin Astronomy Department. "However, we've had a hard time seeing the signature of a collapse."

Evans and his associates, Shudong Zhou of the University of Illinois and Carsten Kompe and C.M. Walmsley of the Max Planck Institute for Radioastronomy, Bonn, Germany, have found the signature of collapse by measuring the velocity of gases in the could, which is one-and-a half light years in diameter. They have discovered that the gases on the near side of the cloud, while those on the far side are hunting toward it at a comparable velocity. This demonstrates that the entire cloud is collapsing toward its center.

The cloud, known as B335, was discovered early in the century by the American astronomer Edward Emerson Barnard. It is invisible to the eye, appearing only as a black, starless area through a telescope. This is because the molecules do not possess enough energy to radiate at wavelengths visible to the eye, yet the dust in the cloud blots out the light of stars behind it.

The cloud is "visible" at infrared and radio wavelengths, and it is at both of those wavelengths that the astronomers have accumulated their data. The radio waves generated by the molecules colliding in the cloud are particularly important because such waves freely pass through the dust and can be analyzed with ground-based radio telescopes. The infrared radiation given off by the cloud is not important in determining whether the gases are in motion, Evans explains, but nonetheless is crucial to determine that the cloud is giving off more energy than it is absorbing from other stars.

Determining that the gases are moving is a feat accomplished though knowledge of the behavior of light, Evans points out. Light and other types of electromagnetic radiation such as radio waves and infrared always travel at the same...