The isotopes -- special forms of atomic nuclei, such as aluminum-26, calcium-41 and beryllium-10 -- can form in the X-ray solar flares of young stars in the Orion Nebula, which behave just like our Sun would have at such an early age.

The finding, based on observations by the Chandra X-ray Observatory, has broad implications for the formation of our own Solar System.

Eric Feigelson, professor of astronomy and astrophysics at Penn State, led a team of scientists on this Chandra observation and presented these results in Washington, D.C., Thursday at a conference entitled "Two Years of Science with Chandra."

"The Chandra study of Orion gives us the first chance to study the flaring properties of stars resembling the Sun when our solar system was forming," said Feigelson. "We found a much higher rate of flares than expected, sufficient to explain the production of many unusual isotopes locked away in ancient meteorites.

"If the young stars in Orion can do it, then our Sun should have been able to do it, too."

Scientists who study how our Solar System formed from a collapsed cloud of dust and gas have been hard pressed to explain the presence of these extremely unusual chemical isotopes.

The isotopes are short-lived and had to have been formed no earlier than the creation of the Solar System, some five billion years ago. Yet these elements cannot be produced by a star as massive as our Sun under normal circumstances. (Other elements, such as silver and gold, were created long before the creation of the solar system.)

The perplexing presence of these isotopic anomalies, found in ancient meteoroids orbiting the Earth, led to the theory that a supernova explosion occurred very close to the Solar System's progenitor gas cloud, simultaneously triggering its collapse and seeding it with short-lived isotopes.

Solar flares could produce such isotopes, but the flares would have to be hundreds of thousands of times more powerful and hundreds of times more frequent than those our Sun generates.

Enter the stars in the Orion Nebula.

This star-forming region has several dozen new stars nearly identical to our Sun, only much younger. Feigelson's team used Chandra to study the flaring in these analogs of the early Sun and found that nearly all exhibit extremely high levels of X-ray flaring -- powerful and frequent enough to forge many of the kinds of isotopes found in the ancient meteorites from the early solar system.

"This is a very exciting result for space X-ray astronomy," said Donald Clayton, Centennial Professor of Physics and Astronomy at Clemson University. "The Chandra Penn State team has shown that stellar-flare acceleration produces radioactive nuclei whether we want them or not. Now the science debate can concentrate on whether such irradiation made some or even all of the extinct radioactivities that were present when our solar system was formed, or whether some contamination of our birth molecular cloud by external material is also needed."

"This is an excellent example of how apparently distant scientific fields, like X-ray astronomy and the origins of solar systems, can in fact be closely linked," said Feigelson.

The Orion observation was made with Chandra's Advanced CCD Imaging Spectrometer, which was conceived and developed for NASA by Penn State and Massachusetts Institute of Technology under the leadership of Gordon Garmire, the Evan Pugh Professor of Astronomy and Astrophysics at Penn State.

The Penn State observation team includes Pat Broos, James Gaffney, Gordon Garmire, Leisa Townsley and Yohko Tsuboi. Collaborators also include Lynne Hillenbrand of CalTech and Steven Pravdo of the NASA Jet Propulsion Laboratory. - By Barbara K. Kennedy

(Editor's Note: A color image of the Orion Nebula taken with the Chandra X-ray Observatory is available on the web at this URL.)

[Contact: Eric Feigelson, Barbara K. Kennedy ]

07-Sep-2001