Epsilon Eridani: An early solar system?


SCIENCE NEWS, VOL 154, AUGUST 8, 1998, p. 91


Among the handful of young stars known to be encircled by thinning rings of dust--a signpost of planet formation--one nearby star stands our from the rest. New observations reveal that Epsilon Eridani may have a planetary system similar to our own. In age, mass, and the position of its newly discovered dust ring, the star bears a close resemblance to what the solar systeln is thought to have looked like when it was just a few hundred million years old. Examining the star by light emitted at submillimeter wavelengths, astronomers have found a ring of dust at roughly the same distance at which the Kuiper belt, a reservoir of comets, orbits the sun. A bright spot within the ring could represent a dense patch of dust trapped by the gravity of an unseen planet, says Jane S. Greaves of the Joint Astronomy Centre in Hilo, Hawaii. Greaves and her colleagues observed the star wlth a high-resolutlon camera attached to the James Clerk Maxwell Telescope atop Mauna Kea in Hawaii.


Although comets radiate too faintly at submillimeter wavelengths to be seen, she notes, collisions of comets could generate a dust ring like the one her team found.


"What we see looks like the comet belt on the outskirts of our solar system, only younger," says Creaves. She notes that the region inside the ring is relatively dust-free. but it still has 1,000 times as much material as the inner part of the present-day solar system. The new images of the star fit with the standard model of the early svlar system at a time when most dust had coalesced into planets, but "there was still lots of stuff whizzlng around and impacting the Earth." Gresves says.


Visible to the naked eye, Epsilon Eridani lies only 10 light-years from the solar system and is nearly as massive as the sun. At 500 million to 1 bllllon years old, it is a youngster compared with the 4.5-billlon-year-old sun but still old enough to have fully formed planels. In contrast, three other stars now known to have dust rings--Vega, Fomalhaut, and Beta Pictoris-- are much younger and more massive than the sun (SN: 4/25/98, p 260).


Greaves reported the findings last month in Santa Barbara, Calif., at a conference on protostars and planets. She and her collaborators will also describe the observations in an upcmming ASTROPHYSICAL JOURNAL LETTERS. -RC