A group of scientists from the University of Queens in Belfast, Northern Ireland, and the Max Planck Institute for Solar System Research, Germany, decided to test how well the Earth is visible to possible representatives of other civilizations trying to observe planetary transits in the same way as we do today using our own means. observations such as NASA's Kepler space telescope ("Kepler").
The Kepler Space Observatory, which searches for new exoplanets, uses the so-called "transit method". The essence of the method consists in registering decreases in the brightness of a star, observed during the passage, or transit, in front of it of an exoplanet, blocking a part of the starlight.
In their work, this group of astronomers, led by Robert Wells of Queens University in Belfast, identified parts of the sky from where the transits of the planets of the solar system can be seen. The study notes that the probability of detecting transits of terrestrial planets (Mercury, Venus, Earth, Mars) from the surfaces of other planets is higher than the probability of detecting large gas planets, since the factor determining this probability is most significantly the distance from the Sun which in the case of terrestrial planets turns out to be much less than in the case of gas giants.
Based on a set of several thousand known exoplanets, the researchers calculated that the transit of one or more of the terrestrial planets could be observed from the surfaces of 68 planets. Nine of these planets are located so that from their surfaces it is possible to observe the transit of the Earth along the disk of the Sun, although, however, all these planets are currently classified by scientists as uninhabited.
In the future, the Wells team plans to continue their research, searching for planets from which the transit of the Earth can be observed using the Kepler space telescope and analyzing their potential habitability.
The work has appeared in the Monthly Notices of the Royal Astronomical Society.