PHOENIX — Infant stars swaddled in dust have been discovered as they emerge from a dark interstellar gas cloud, giving scientists a new model of stellar formation and suggesting that sunlike stars are born with the raw materials for planets.
The stars described by astronomers last week are among the youngest ever photographed, and were found by using a sensitive new infrared instrument able to penetrate the veil of dark gas and debris that blocks the view of forming stars.
In the past, scientists suspected that most stars formed in large nebulae, such as Orion, by churning out thousands of stars bound in clusters by gravity. The new discovery found that most stars in the Milky Way may have formed in "aggregates" or small stellar incubators.
Astronomer Karen M. Strom of the University of Massachusetts at Amherst and her husband, Stephen E. Strom, along with co-researcher K. Michael Merrill of the Kitt Peak National Observatory in Tucson, said their images appear to show girdles of dust particles condensing around each star to form asteroid-like "planetesimals."
Astronomers, using the orbiting Infrared Astronomical Satellite (IRAS), have found the discs of dust around a few other stars such as Beta Pictoris and Vega. They concluded that perhaps one in four stars are formed with these protoplanetary discs.
Stephen Strom, however, argued that such discs are intrinsic to star formation. "All stars . . . must have discs. It's necessary for their development. The question is, do they evolve differently (depending on the star and the way it was formed)? . . . That's something that we're trying to find out."
He said he agrees with other astronomers' estimate that these planetesimals may seed the condensation of planets around perhaps 10% to 20% of all stars.
No one, including the Stroms, has seen planets outside Earth's solar system, although ample circumstantial evidence indicates that they should exist. Finding the first planets is a compelling goal for astronomers.
The Stroms said they decided to look for star formation in the interstellar gas cloud Lynds 1641 after IRAS saw several inviting infrared light sources there. After studying the cloud, which is 1,500 light-years from Earth, Karen Strom said she chose to investigate the five densest areas.
A light-year is a measure of distance based on how far light travels in one year, or roughly 5.8 trillion miles.
