In the last decade , we have discovered thousands of exoplanets . Now , stargazer from Germany and Northern Ireland have uncover how many of these populace could possibly find us as clearly as we can notice them .
They estimated that 68 out of the known 3,667 exoplanets are place in the right attitude to spot at least one or more planets in the solar system . Nine of them are in an ideal place to detect Earth , but none of them are inhabitable . However , statistical estimate hint that 10 undiscovered planets could both see Earth and be in the inhabitable zone . This analytic thinking is report in theMonthly Notices of the Royal Astronomical Society .
” We estimate that a randomly set commentator would have roughly a 1 in 40 hazard of observing at least one planet , " co - author Katja Poppenhaeger from Queen ’s University Belfast read in astatement . " The chance of detecting at least two planets would be about ten times lower , and to detect three would be a further ten times little than this . "
If we can see them , why ca n’t they see us ? It ’s all a matter of how we find exoplanets . The extremely successfulKepler missiondetects them by looking at how planet that pass through in front of their champion kibosh a small fraction of light . If they see this happening at regular intervals , this suggest a planet is orbiting that star .
For a hypothetical alien civilisation to chance Earth , they will want to inhabit the narrow band of the sky from where a transit is visible . Although the inclination of the orbit of the other eight planet is only a few degrees away from Earth ’s , that would be enough for a scope like Kepler to miss out on some of the other planet . The report indicate no more than three satellite can be see from any localisation .
Distance from the adept also recreate a central office . The inquiry estimates that although the rocky planets are smaller , just being near the Sun makes us more probable to be spotted . ” Larger satellite would by nature block out more ignitor as they pass in front of their star , ” explained principal author Robert Wells of Queen ’s University Belfast . ” However the more important agent is actually how end the satellite is to its parent star – since the terrestrial planets are much unaired to the Sun than the gas giants , they ’ll be more likely to be check in transportation system . ”
How planets transit a star is not the only way to see exoplanets , but it has been highly successful . peradventure there are aliens out there with much salutary telescopes that have discover us with other methods , but if they spotted us through the transportation method acting , they can only exist on these handful of planet .
