In new research, scientists estimate that planets in about 1715 Star Systems are capable of observing the Earth transit the Sun (pass in front of it). Out of these 1715 Star Systems, scientists have found that 46 Star Systems will be able to identify life on Earth by intercepting human broadcasts- radio, television, etc! In the 46 star systems, there are about 29 potentially habitable planets.
How did Scientsists make these observations?
Lisa Kaltenegger, a professor of astronomy and director of the Carl Sagan Institute at Cornell University says “One way we find planets is if they block out part of the light from their host star”. This is called transit method. About 70% of all exoplanets discovered by humans have been discovered using this method. The habitable zones of the star systems are estimated by studying the properties of the star.
To list the stars capable of watching the Earth transit, scientists used European Space Agency’s Gaia catalogue of star positions and motions. Careful analysis and Information from the catalogue allowed scientists to shortlist the 29 habitable planets capable of observing an Earth transit in any time between 5000 years ago to 5000 years in the future
Some of the Star Systems in the list
Ross 128, a red-dwarf star located 11 light-years away in the virgo constellation is close enough to receive Earth Broadcasts. It has a planet twice the size of Earth and its position would allow any intelligent life to observe the Earth Transit but it lost that capability 900 years ago.
Any life form on one the two known planets orbiting Teergarden’s star, which is located 12.5 light years away, will be in position to observe the Earth transit in 29 years.
Another star called Trappist-1, which is located 45 light years away, has 7 planets out of which 4 are in the habitable zone. But the star system will not be able to observe Earth Transits for the next 1642 years.