In a bid to find how alien observers might be able to detect earth, scientists have found that at least nine exoplanets were ideally placed to observe the transits of our world.
Scientists from Queen's University Belfast in the UK and the Max Planck Institute for Solar System Research in Germany reversed exoplanet-hunting, as they looked for an alien planet that could spot the earth.
Researchers identified parts of the distant sky which could serve as vantage points for observing planets in our Solar System as they passed in front of the Sun.
They concluded that the planets Mercury, Venus, Earth, and Mars had a greater likelihood of being spotted than the more distant 'Jovian' planets Jupiter, Saturn, Uranus, and Neptune, despite their much larger size.
"Larger planets would naturally block out more light as they pass in front of their star," said Robert Wells, a PhD student at Queen's University Belfast, PTI reported.
"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," said Wells, lead author of the study published in the journal Monthly Notices of the Royal Astronomical Society.
The study, titled ''Transit Visibility Zones of the Solar System Planet'', was recently published in the Monthly Notices of the Royal Astronomical Society. The team led by Wells considered whether or not Earth would be detectable from other star systems using the Transit Method.
In the method, astronomers observe stars for periodic dips in brightness, which are attributed to planets passing (ie, transiting) between them and the observer. Wells and his colleagues sought to determine if Earth would be visible to any species conducting observations from vantage points beyond our Solar System.
They determined that the terrestrial planets that are closer to the Sun (Mercury, Venus, Earth and Mars) would easier to detect.