Aliens on at least nine planets beyond the solar system could see - and potentially study - Earth, scientists have claimed. The new research from Queen's University Belfast offers a whole new angle to exoplanet-hunting, looking at how an alien observer might be able to detect Earth using our own methods.
The scientists 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". 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. 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.
The scientists 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" (Image: PA)
The research, conducted alongside the Max Planck Institute for Solar System Research in Germany, was published in the journal Monthly Notices of the Royal Astronomical Society . Scientist Robert Wells, from Queen's University Belfast, told the royal Astronomical Society :
“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 l’ikely to be seen in transit.”
Katja Poppenhaeger, a co-author of the study, adds:
“We estimate that a randomly positioned observer would have roughly a 1 in 40 chance of observing at least one planet. The probability of detecting at least two planets would be about ten times lower, and to detect three would be a further ten times smaller than this.”