January 2001

From Yale University

168 New stars near the Orion region discovered by Yale, Venezuelan and Smithsonian scientists

Finding could help pinpoint time of planet formations

A team of astronomers from Yale, Venezuela and the Smithsonian Institution have identified 168 young stars, about half the mass of the sun, in a region called the Orion star forming complex, which is 1,400 light years from Earth.

"This is just the tip of the iceberg," said César Briceno, who started the study as a research scientist in Yale’s physics department in 1998 and is now a staff astronomer at the Centro De Investigaciones de Astronomia in Venezuela. "This is ongoing work. The 168 stars were found in the very first strip of sky we observed; the entire survey area is about six times that size, so we expect to find a few thousand stars before our study is done."

Published in today’s issue of Science, the results of the study, Briceno said, offer important constraints for theories on how fast planetary systems can form. "The stars we found are all between one and 10 million years old. Our study shows evidence that the gaseous, dusty disks surrounding the youngest stars have largely disappeared in their 10 million-year-old siblings, possibly because the dust in the disk has coagulated into larger bodies like planets. These preliminary results suggest that solar-like stars can form planets in about 10 million years; a lot faster than previously thought."

The stars were identified using a large CCD Mosaic digital camera developed jointly between Yale and Venezuelan institutions. It is installed on a powerful wide-field telescope at the Venezuela National Observatory, located at an elevation of 12,000 feet. This unique combination allows researchers to cover very large areas of the sky in a very efficient way.

"This is the first time young stars have been discovered using this innovative technique," said Briceno. "We took pictures of the same area of sky over and over again to identify the young stars."

Using software specially developed by Yale astronomy graduate student Katharine Vivas, the team picked candidates among stars that would vary in brightness over days and weeks. Young stars were then confirmed by follow-up observations conducted at the Wisconsin-Indiana-Yale National Optical Astronomical Observatories (WIYN) telescope and the 60-inch telescope at the Smithsonian Astrophysical Observatory in Arizona.

While research efforts have focused on targeting the youngest stars, Briceno said that identifying older stars is crucial in determining the time scales for the coagulation of dust grains into larger bodies such as planets. These older stellar populations are difficult to find because they are widely spread over the sky, and their molecular clouds have been dispersed and so no longer serve as markers for their positions.

Other researchers on the study included Jeffrey Snyder and Peter Andrews of Yale’s physics and astronomy departments; Nuria Calvet of the Centro de Investigaciones de Astronomia in Venezuela and the Smithsonian Center for Astrophysics; Lee Hartmann, and Perry Berlind of the Smithsonian Center for Astrophysics; Ricardo Pacheco of the Centro de Investigaciones de Astronomia and the Universidad de los Andes in Venezuela; and David Herrera, Lysett Romero and Gerardo Sanchez of the Centro de Investigaciones de Astronomia.

This study is funded by grants from the National Science Foundation and the NASA Origins of Solar Systems Program, and with support from the Venezuelan Ministry of Science and Technology.












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