Remember, how excited we were when we thought there are thousands of exoplanets in our galaxy? Scientists even daydreamed about living on those exoplanets, which are in the habitable zone. Well, don’t pack your bags yet as about 11 percent of such exoplanets may be false positive.
In 2009, NASA launched a space observatory, Kepler, and so far, it has done nothing but look out for signals of exoplanets in other solar systems. Kepler not only explored such planets but also found thousands of exoplanets and confirmed that every one in five Sun-like stars have the Earth-like planet in the habitable zone. Furthermore, it continues to wait for unexpected dips in brightness in stars. Why? A sudden drop in the brightness means there must be a planet revolving around the host star. Therefore, Kepler has seen thousands and thousands of dips and concluded that there are colossal exoplanets out there, revolving outside our solar system. In 2015, NASA introduced Kepler-452b to the world. Kepler-452b is an exoplanet that orbits around the Sun-liked star Kepler-452 in the constellation Cygnus, 1,400 light-years from the Earth. Scientist even nicknamed it the Earth’s cousin or Earth 2.0. However, some critics thought these readings are too good to be true and believe Kepler-452b may not be the Earth’s cousin after all.
A new study, published in The Astrophysical Journal, scrutinizes the Kepler’s approach to detect whether a planet is an exoplanet or not. As per the study, scientists used another telescope to double-check the exoplanets discovered by Kepler. In numerous cases, the brightness dip was not caused by any revolving exoplanet, but noise in data sent back to the Earth or some other object blocking the star’s light. Since, Kepler seems to find more and more potential exoplanets, scientists used different strategy for conformation. If only a signal shows 99 percent of statistical chance for a planet, then only it was regarded as a “confirmed” planet. However, according to the new study, NASA’s analysis did not consider the instrumental errors of the telescope.
Scientists used Kepler-452b as test for their research to confirm their suspicions. They considered the instrumental errors in calculations and concluded that odds that Kepler-452b is an exoplanet are somewhere between 16 to 92 percent. Even though, Kepler telescope is pretty reliable to detect an exoplanet, Kepler-452b falls below the threshold of 99 percent. Furthermore, if every detected exoplanet candidate is similar to Kepler-452b, only 9 out of 10 signals are of an actual planet. However, the possibility for a potential planet is fewer than this. Some exoplanet candidates were checked using another technique that ransacks “wobbles” in the star caused by the gravitational force of the revolving planet. However, Kepler-452b is too small for that.
In search of the Earth-like planets, data must be handled carefully as these planets are usually small and distant from their host stars. Moreover, signals claiming the existence of exoplanets can easily be a technical glitch or an instrumental error, which is the major problem in finding for the worlds like ours. Therefore, scientists believe the only instrument that can settle the question of exoplanet is Hubble Telescope. However, observing by Hubble and conforming the status of Kepler-452b as planet or not is a big challenge owing to its limited resources. Therefore, it is likely that scientists will now keep on second-guessing other exoplanet candidates till a better instrument is developed.