Smaller Solar System Shows Several Similarities

One of the solar system’s little siblings is even more like our own than researchers had previously thought, according to a new study co-authored by a scientist at the Harvard-Smithsonian Center for Astrophysics.

A team of astronomers, including Harvard’s Massimo Marengo, found a triple-ring system surrounding Epsilon Eridani, the ninth closest star to the Sun. The rings suggest the existence of three or more planets around the star, according to their paper, which will be published in a forthcoming issue of The Astrophysical Journal.

Using NASA’s Spitzer Space Telescope, the astronomers, led by Dana Backman of the California-based SETI Institute, discovered the existence of two asteroid belts and an icy outer ring surrounding Epsilon Eridani.

The inner ring appears identical in composition and mass to the asteroid belt in our solar system located between Mars and Jupiter, and the outer one is 20 astronomical units from Epsilon Eridani—about the distance from Uranus to the Sun. The outer ring of icy mini-planets surrounding Epsilon Eridani is similar to the Kuiper Belt that is located just beyond Pluto.

Marengo said that he and his team of astronomers think that the gaps between the rings were created by the process of planetary formation and are held in place by orbital gravity. Some of these possible planets may even be similar to Earth.

“The real Holy Grail here that astronomers are looking for in my field is to be able to say, here, somewhere, is a planet that resembles the Earth—not only in size or mass, but also in composition and atmospheric conditions,” Backman said, referring to the possibility of finding “a life-bearing planet.”

Epsilon Eridani holds a particular hope in the search for extraterrestrial life. Deemed one of the “Fabulous Four” by the Spitzer telescope team, Epsilon Eridani is one of four stars that have debris disks—a sign that planets may have formed. The star shares many physical similarities with the Sun, but it is only 850 million years old compared to the Sun’s 4.5 billion.

“It provides a window like a time machine to see what was happening to the Sun at the same age that life was starting on Earth,” Marengo said.

Follow-up research will include the launch of Project Kepler, a first-of-its-kind NASA spacecraft mission that will look for Earth-sized planets located at similar distances from their respective stars—planets that might be friendly to life.

The telescope is scheduled to launch in the spring of 2009, and Backman said that it will first look at Epsilon Eridani, in part because of the discovery of its triple-ring system.

“I’m in career ecstasy right now because it came out so nicely and it all worked,” Backman said. “It is finally ending up to be joyful.”

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