Science + Technology

Astronomers Discover Nearby Star System Like Our Solar System


An international team of astronomers from the Joint Astronomy Centre(JAC) in Hawaii, UCLA and the Royal Observatory in Edinburgh announcedtoday the discovery of a ring of dust particles around a nearby star, EpsilonEridani, that appears to signify a solar system very similar to our own.

The ring is "strikingly similar" to the inner comet zone inour solar system, and shows an "intriguing" bright region thatmay be particles trapped around a young planet, said JAC astronomer JaneGreaves, who led the research team.

"What we see looks just like the comet belt on the outskirts ofour planetary system, only younger," said Greaves, who presented thefindings today at the Protostar and Planets conference in Santa Barbara."It's the first time we've seen anything like this around a star similarto our sun. In addition, we were amazed to see a bright spot in the ring,which may be dust trapped in orbit around a planet."

Greaves was a member of the international team that reported new imagesof dusty disks around the hotter stars Fomalhaut and Vega in April. Shesaid the new image of Epsilon Eridani is more important for a number ofreasons:

"Epsilon Eridani is far more similar to our sun than either Vegaor Fomalhaut," she said. "This star system is a strong candidatefor planets, but if there are planets, it's unlikely there could be lifeyet. When the Earth was this young, it was still getting very heavily bombardedby comets and other debris.

"This is also a star in our neighborhood -- only about 10 lightyears away -- which is why we can see so much detail in the new image."

"If an astronomer could have measured what our solar system lookedlike four billion years ago, it would look very much like Epsilon Eridanilooks today," said Benjamin Zuckerman, UCLA professor of physics andastronomy. "This is a star system that quite resembles our solar system;it's one thing to suspect that another such system exists, but anotherto actually see it, and this is real observational evidence."

Epsilon Eridani, visible to the eye, is in the constellation Eridanus(the River), which stretches from the foot of Orion (near the bright starRigel) to the ninth brightest star in the sky, the southerly Achernar (barelyvisible from the United States and Europe). Epsilon Eridani is among the10 closest star systems to the Earth.

The research team -- which also includes astronomers from the Universityof Arizona, the University College London, and the Rutherford AppletonLaboratory -- has submitted its findings to the Astrophysical Journal Letters,the most widely-read scholarly journal in astronomy.

Beyond Pluto in our solar system is a region called the "Kuiperbelt" containing more than 70,000 large comets, and hundreds of millions,if not billions, of smaller ones. The image obtained by Greaves' team showsdust particles that the astronomers believe is analogous to our Kuiperbelt at the same distance from Epsilon Eridani as the Kuiper belt is fromour sun. Although the image cannot reveal comets directly, the dust thatis revealed is believed to be debris from comets, Greaves said.

The region near Epsilon Eridani interior to its dust belt contains about1,000 times more dust than the comparable region of our solar system, whichmay mean that Epsilon Eridani has about 1,000 times more comets, the astronomerssaid. Epsilon Eridani is estimated to be only 500 million years to 1 billionyears old; our sun, is estimated to be 4.5 billion years old, and its innerregion is believed to have looked very similar during the earlier age.

In our solar system, the first 600 million years was a time of "heavybombardment" when the planets were assaulted by massive meteoritesand other celestial objects until the gravitation of Jupiter and Saturncleaned out these destructive objects. Life on Earth probably did not startuntil after the era of heavy bombardment, said JAC astronomer Wayne Holland.

How was the new image obtained?

The new image -- which is from short-radio wavelengths, and is not anoptical picture -- was obtained using the 15-meter James Clerk MaxwellTelescope at the Mauna Kea Observatory in Hilo, Hawaii. The JCMT is theworld's largest telescope dedicated to the study of light at "submillimeter"wavelengths. The team of astronomers used a revolutionary new camera calledSCUBA (Submillimeter Common User Bolometer Array), which was built by theRoyal Observatory in Edinburgh (which is now the UK Astronomical TechnologyCentre). SCUBA uses detectors cooled to a tenth of a degree above absolutezero (-273 degrees Celsius) to measure the tiny amounts of heat emissionfrom small dust particles at a wavelength close to one-millimeter.

Implications and mysteries of the new discoveries

What is the significance of the similarity between Epsilon Eridani andour own solar system?

"The implication is that if there is one system similar to oursat such a close star, presumably there are many others," Zuckermansaid. "In the search for life elsewhere in the universe, we have neverknown where to look before. Now, we are closing in on the right candidatesin the search for life."

Epsilon Eridani is probably too young to support even primitive life,the astronomers said, but there probably are other similar star systemsthat are billions of years older, and are good candidates to search forlife. Although astronomers have not yet located a star system that is theright age, orbited by an Earth-mass planet that has the right atmosphereto support life, they are getting closer.

The region near Epsilon Eridani that is partially evacuated indicatesthat planets may have formed, the astronomers said; the presence of planetsis the most likely explanation for the absence of dust in this region becauseplanets absorb dust, they said.

What is the bizarre bright spot in the image obtained by the astronomers?

"There may be a planet stirring up the dust in the ring and causingthe bright spot," said Bill Dent of the Royal Observatory, Edinburgh,"or it could be the remnants of a massive collision between comets."

Epsilon Eridani is about three-quarters as massive as the sun, but onlyone-third as luminous. When astronomer Frank Drake conducted the firstserious search for radio signals from other civilizations in the late 1950s,Epsilon Eridani was one of the two stars he studied. Today, researchersknow something Drake did not: Epsilon Eridani is much too young to haveintelligent life. However, the new image suggests there are planets, andperhaps life in the future, Greaves said.

The JCMT is operated by the Joint Astronomy Centre, on behalf of theUK Particle Physics and Astronomy Research Council, the Netherlands Organizationfor Scientific Research, and the Canadian Research Council. The NationalScience Foundation and NASA supported the UCLA research on this project.

In addition to Greaves, Holland, Zuckerman and Dent, the astronomerson the project are Gerald Moriarty-Schieven and Tim Jenness at JAC; HaroldButner at the University of Arizona, Tucson; Walter Gear at UniversityCollege London; Helen Walker at the Rutherford Appleton Laboratory; andUCLA graduate students Richard Webb and Chris McCarthy.

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