Giant comets and their debris may present a significantly higher risk to human life than asteroids and should be studied more closely, according to a team of British astronomers.

The astronomers say that hundreds of “centaurs,” huge orbs of ice and dust that usually are between 30 and 60 miles wide, have been discovered in far-flung parts of space in the past two decades. The researchers say the massive comets travel along unstable orbits near the four gas giants of Jupiter, Saturn, Uranus and Neptune.

Centaurs seldom enter the inner solar system, the astronomers say, but their research indicates that the gravitational pull of those four planets can redirect one toward Earth. One centaur will cross Earth’s orbit about every 40,000 to 100,000 years, according to their research.

As the centaurs approach the Sun, they disintegrate and spray debris throughout space. The astronomers say some of that debris will inevitably impact the Earth.

One centaur “contains more mass than the entire population of Earth-crossing asteroids found to date,” according to a news release from the Royal Astronomical Society, which published the study in the December issue of its journal, Astronomy & Geophysics.

Astronomers from Armagh Observatory and Buckingham University performed the research.

One of the study’s co-authors, Bill Napier, said in a statement that scientists have devoted a lot of time and energy to analyzing the risk of an asteroid colliding with the Earth, particularly in the past three decades.

“Our work suggests we need to look beyond our immediate neighborhood too, and look out beyond the orbit of Jupiter to find centaurs,” Napier said. “If we are right, then these distant comets could be a serious hazard, and it’s time to understand them better.”

NASA officials have publicly stated that there’s no known asteroid or comet that has any chance of impacting the Earth within the next 100 years.

However, scientists didn’t discover a space rock that came within 300,000 miles of the Earth – about 1.3 times the distance between the planet and the moon – until three weeks before it zoomed by this past Halloween.