Dec 23, 2015 10:39 AM EST By Russell Westerholm, UniversityHerald Reporter

When a team of researchers expanded their view of asteroids potentially threatening for Earth, they found much more than previously tallied.

According to Agence France Press, authors of a study published in the journal Astronomy and Geophysics examined large comets called centaurs in an elliptical, unstable orbit around the sun beyond Neptune. Many of these centaurs, which range from about 30 to 60 miles wide, were discovered within the last two decades.

These comets do not head toward Earth often, but they do break apart and fling small pieces all about.

"The disintegration of such giant comets would produce intermittent but prolonged periods of bombardment lasting up to 100,000 years," the researchers wrote in their study.

Most near-Earth asteroids on record are from the asteroid belt in between Mars and Jupiter. The researchers noted centaurs breaking apart and producing smaller pieces of debris is dangerous because a single comet's mass is great enough to produce a host of near-Earth asteroids.

"In the last three decades, we have invested a lot of effort in tracking and analyzing the risk of a collision between the Earth and an asteroid," study co-author Bill Napier, of the University of Buckingham, told AFP. "Our work suggests we need to look beyond our immediate neighborhood too, and look out beyond the orbit of Jupiter to find centaurs.

"If we are right, then these distant comets could be a serious hazard, and it's time to understand them better."

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