Earth could be in serious danger due to outer space objects, but it isn’t asteroids that we should be panicking about, experts from Armagh Observatory and the University of Buckingham warn in a new Astronomy and Geophysics study – it’s comets that pose the real danger.

Specifically, the threat comes in the form of giant comets known as centaurs, which the authors explained are typically up to 100 km large and more massive than all of the near-Earth asteroids discovered thus far combined. These centaurs travel along unstable orbits that cross the paths of the outer planets, whose gravitational fields could deflect them towards our planet.

According to AFP and UPI reports, their calculations indicate that such a phenomenon occurs once every 40,000 to 100,000 years. As a centaur traveled closer to Earth, it would disintegrate in the atmosphere, leaving behind fragments likely to impact with the planet’s surface. Recent research has revealed that there are hundreds of these comets in the outer planetary system.

“The disintegration of such giant comets would produce intermittent but prolonged periods of bombardment lasting up to 100,000 years,” the study authors wrote, adding that such an event may be “inevitable” and that the “assessment of the extraterrestrial impact risk based solely on near-Earth asteroid counts, underestimates its nature and magnitude.”

Such an event could be worse than a nuclear winter, the authors claim

As team members Professors Bill Napier and Duncan Steel m the University of Buckingham and Professor Mark Bailey and Dr. David Asher from Armagh Observatory said in a statement, there was a centaur arrival that took place about 30,000 years ago. Debris from the massive comet was likely scattered throughout the inner solar system.

Thanks to the research of geologists and paleontologists, the scientists were also able to identify several episodes of environmental upheaval that occurred between 10,800 BCE and 2,300 BCE that were said to be consistent with the behavior of these comets. They believe that some of the planet’s most extreme mass extinction events could actually be linked to centaurs.

“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,” Professor Napier explained. “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.”

As the team told AFP, no such event is “known to be imminent,” though they cautioned that the behavior of comets was somewhat unpredictable. Were something like this to happen, however, they said that it could inject “a mass of dust and smoke comparable to that assumed in nuclear winter studies” into the atmosphere. “Thus, in terms of magnitude, its ranking among natural existential risks appears to be high.”

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Feature Image: Because they are so distant from the Earth, Centaurs appear as pinpricks of light in even the largest telescopes. Saturn’s 200-km moon Phoebe, depicted in this image, seems likely to be a Centaur that was captured by that planet’s gravity at some time in the past. Until spacecraft are sent to visit other Centaurs, our best idea of what they look like comes from images like this one, obtained by the Cassini space probe orbiting Saturn. NASA’s New Horizons spacecraft, having flown past Pluto six months ago, has been targeted to conduct an approach to a 45-km wide trans-Neptunian object at the end of 2018. (Credit: NASA/JPL-Caltech/Space Science Institute)

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