Swarthmore Researchers Discover Group of Young, Nearby Stars

Newly Identified Stars Could Lead to Better Understanding of
Planet Formation

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.

For an earlier version of this news release and additional
background and illustrations, visit
http://astro.swarthmore.edu/press_release/

For interviews or additional information, contact Eric
Jensen at 610-328-8249 or ejensen@swarthmore.edu and/or
Rabi Whitaker at 610-690-5237 or rwhitak1@swarthmore.edu .