Asteroid Belt Discovered Around Our Sun's "Twin"

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George Rieke is a study co-author and principal investigator with the Spitzer Space Telescope who is based at the University of Arizona in Tucson. "Because this belt has more asteroids than ours, collisions are larger and more frequent, which is why Spitzer could detect the belt," he said.

"Our present-day solar system is a quieter place, with impacts of the scale that killed the dinosaurs occurring only every hundred million years or so," he added.

Astronomers have previously detected other asteroid belts around two far younger, more massive suns. But researchers believe the latest discovery—an asteroid belt arrayed around a mature star—will reveal more about our sun and whether our solar system is the norm or the exception.

Earth-Like Planets

"We all want to understand, ultimately, how common our own solar system is and how common habitable planets like our own Earth might be throughout the cosmos," said Jonathan I. Lunine, a physics and planetary science professor at the University of Arizona.

Scientists say they don't know yet if any planets orbit HD69830. But they do know where an Earth-like planet—featuring liquid water on its surface for billions of years—would have to be located.

HD69830 "is a bit dimmer and younger than our own sun, perhaps half the brightness of our own sun," Lunine explained. "So to have an 'Earth' with the same conditions we'd want it to move from 1 astronomical unit [AU] to 0.9 or perhaps 0.8 AU from that star," he said.

One AU represents the mean distance from the Earth to the sun, about 93 million miles (150 million kilometers).

It may or may not be possible for a planet to exist in what some dub the Goldilocks zone (not too hot, not too cold).

Knowing how closely the new asteroid belt orbits its star can tell scientists whether or not an Earth-like planet is possible in this belt, Lunine said.

Even if a terrestrial planet does exist in the Goldilocks zone it would be peppered with asteroid impacts. Extinction-causing impacts on such a planet would likely occur about once every million years—making it debatable whether life could have ever taken hold.

Giant Comet?

Scientists have yet to definitively determine that HD69830 does, indeed, have a massive asteroid belt. They must first rule out a second statistically improbable but intriguing explantion for the Spitzer discovery.

It is possible that the dust detected by Spitzer is from a giant, Pluto-size comet that was bounced into the inner solar system via a "cosmic bank shot" and is leaving a trail of dust as it distinigrates.

The dust does contain silicate crystals, like fosterite, similar to those found in the famous comet Hale-Bopp.

But the theory is a statistical longshot. It is not nearly as likely as the asteroid belt concept, Spitzer scientists say.

Spitzer and ground-based telescopes may soon confirm the asteroid belt theory by scanning the region for water and carbon monoxide—compounds common in comets, but not asteroids.

After confirming that their new observation is indeed an asteroid belt, scientists could focus their attention on the building blocks of a distant star system much like our own.

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