Aliens on at least nine planets 'would be ideally placed to see Earth'
Aliens on at least nine planets beyond the solar system would be ideally placed to detect and observe the Earth, scientists have shown.
The research has echoes of HG Wells's classic sci-fi novel War Of The Worlds in which the author writes about "intellects vast cool and unsympathetic" watching the human race.
There is no evidence of Martians or any other extraterrestrials planning to invade the Earth but the new research suggests we are not well hidden from aliens should they be out there.
The scientists - one of whom is coincidentally named Robert Wells - identified parts of the sky from where various planets in our solar system could be seen passing in front of the sun as they undertake so called "transits".
They calculated that the smaller rocky planets including Earth would be far more easy to spot than the gas and ice giants Jupiter, Saturn, Uranus and Neptune that are further from the sun.
Mr Wells, from Queen's University Belfast, said: "Larger planets would naturally block out more light as they pass in front of their star. However the more important factor is actually how close the planet is to its parent star. Since the terrestrial planets are much closer to the sun than the gas giants, they'll be more likely to be seen in transit."
Of the thousands of known exoplanets, the team identified 68 worlds where observers would see one or more planets in our solar system transiting the sun.
Nine of these planets were "ideally" placed to observe transits of the Earth, although none of them are thought to be capable of hosting Earth-type life.
The research is published in the journal Monthly Notices Of The Royal Astronomical Society.