Researchers Discover Group of Young, Nearby Stars

A Swarthmore College astronomer and his undergraduate research partner have discovered previously unknown young stars relatively close to earth, a discovery that could open the door to new understanding of planet formation.

Eric Jensen, assistant professor of astronomy, and Swarthmore senior Rabi Whitaker announced the discovery earlier this week at the American Astronomical Society Meeting in Seattle. The stars are about 30 million years old -- the approximate age of the sun when planets in our solar system formed -- and only a few hundred light years away from Earth.

Jensen, who studies the processes by which planets form around stars, says the new discovery could be a boon to on-going efforts to gain better understanding of the frequency and speed of planet formation in other solar systems.

"What makes these stars interesting is that their ages are just right for them to be forming planets right now, and their proximity to Earth makes them easier to observe," Jensen said. "These stars are perfect candidates for follow-up observations to help us understand planet formation."

Jensen cautions that it is not yet known whether there are planets orbiting any of these stars. "Nevertheless, the stars will provide a test of how well we understand planet formation," he says. "By observing these stars as part of a larger sample of stars of similar ages, we can get an idea of how frequently stars form planetary systems, and exactly when in a star's life cycle planets are formed."

As is the case with many astronomical discoveries, Jensen and Whitaker did not discover new stars per se, but rather learned something new about stars whose existence had been known. "What's new here is our realization of how young these stars are," says Whitaker, who has been working with Jensen as part of her senior thesis. "If you think of our Sun as middle-aged, these stars are like babies that are only a few weeks old."

The evidence for the stars' youth comes from observations made with the National Science Foundation's Blanco 4-meter (159-inch) Telescope at Cerro Tololo Inter-American Observatory in Chile. Spectra of the stars show the presence of a large amount of the element lithium. As a star ages, nuclear reactions gradually destroy the lithium atoms that were part of its initial chemical makeup. Thus, the more lithium present in a star, the less time the star has had to destroy it, and the younger the star.

While it was once believed that star formation occurred only in large clouds of gas and dust, observations over the past ten years have indicated that at least some stars are formed in relatively small groups, and that some of these groups are nearby, only 100 to 200 light years away.

In addition to the stars announced this week, Jensen expects still more young stars to be found in the near future; the Swarthmore team has more observations of promising candidates scheduled for this coming April.

The National Science Foundation and Swarthmore College supplied funding for Jensen's research.

Located near Philadelphia, Swarthmore is a highly selective liberal arts college with an enrollment of 1,450. Swarthmore is consistently ranked among the top liberal arts colleges in the country.