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According to a new study by astronomers, Earth could be more exposed to a collision with a body from outer space more than ever. According to a study published on Tuesday, the threat is real and we have to look out for giant comets heading our way. Astronomers from the Armagh Observatory and the University of Buckingham say that most of the studies about potential collision are concentrated with celestial bodies lurking the space between Mars and Jupiter, in a report published on the website of the Royal Astronomical Society in the UK.

The discovery of hundreds of comets – called centaurs - in the last two decades, has made astronomers include these giant celestial bodies into the list of potential threats to our planet, even though they have much larger objects than regular celestial bodies. The giant comets called centaurs are between 50 and 100 kilometers in length and have unstable elliptical orbits from regions beyond Neptune, the last planet of our solar system. The orbit of these comets crosses that of planets like Jupiter, Saturn, Uranus and Neptune, whose gravity fields may occasionally divert a comet towards Earth, that is once every 40,000 to 100,000 years.

An image of comet C/2013 US10 captured near Somoskoujfalu, northeast of Budapest,

All comets are disintegrated over time during their journey around the sun. In the case of centaur comets, this process could produce "intermittent but prolonged periods of bombings that would last up to 100,000 years," scientists write in the report

"The disintegration of such giant comets would produce intermittent, but prolonged periods of bombardment lasting up to 100,000 years," the research team wrote in the Royal Astronomical Society journal, Astronomy, and Geophysics. And they argued that "assessment of the extraterrestrial impact risk based solely on near-Earth asteroid counts, underestimates its nature and magnitude."

Intently, in their study, scientists noted that a single centaur contains more mass than the entire population of Earth-crossing asteroids which have been identified to date.

"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," said co-author Bill Napier of the University of Buckingham.

The outer solar system as we now recognise it. At the centre of the map is the Sun, and close to it the tiny orbits of the terrestrial planets (Mercury, Venus, Earth and Mars). Moving outwards and shown in bright blue are the near-circular paths of the giant planets: Jupiter, Saturn, Uranus and Neptune. The orbit of Pluto is shown in white. Staying perpetually beyond Neptune are the trans-Neptunian objects (TNOs), in yellow: seventeen TNO orbits are shown here, with the total discovered population at present being over 1,500. Shown in red are the orbits of 22 Centaurs (out of about 400 known objects), and these are essentially giant comets (most are 50-100 km in size, but some are several hundred km in diameter).

"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."

While in the last decade the theory that the extinction of Dinosaurs was caused by an impact of a similar comet 65 million years ago has lost strength, it still remains as a leading contender for having ended the era of Dinosaurs on Earth.

The group of researchers said that there is no imminent threat, but cometary encounters are and remain largely unpredictable.

"A centaur arrival carries the risk of injecting, into the atmosphere... a mass of dust and smoke comparable to that assumed in nuclear winter studies," wrote the researchers, referring to the hypothesized climate effects from the soot that would be released by firestorms caused in an atomic war.

"Thus, in terms of magnitude, it's ranking among natural existential risks appears to be high," said researchers in the study.