Small exoplanet mass 254 light-years away measured with unprecedented precision

A new extrasolar planet has been analyzed thanks to the NASA Kepler space telescope that does not want to know how to retire. This planet turns out to be the one for which the mass has been identified in a more precise way than any other exoplanet so small, at least until today. The same researcher who carried out the measurement, Aaron Hamann, first author of the study, declares that it was a “completely unexpected” thing.

There is talk of a “record precision” allowed precisely by the ways in which this planet, along with another, revolves around its star. The first time Kepler scoured the K2-146 star, located 258 light-years away from us, the scientists noticed an irregular darkening pattern. We talk about the darkening caused by the passage of the planet in front of the star from our point of view, which allows us to implement the so-called “transit method,” one of the most used to discover planets beyond the solar system.

Comparing the data of the first passage with those of the second and third, always identified by Kepler years later, the scientists understood that this irregularity was caused by a second smaller planet that pulled the first planet by gravitational force. Every time they approached, a sort of “mini slingshot effect” was created, as reported by Hamann himself.

If this strong gravitational bond between the two planets is added that the two planets orbit around their star in a few days (3.99 days for the largest and 2.66 days for the smallest), there is also a strong effect on the orbit so much that sometimes they can have significantly shorter or longer years: “It would be as if your birthday sometimes arrived almost a month before or later than you would normally expect,” reports the researcher to cite a case in point.

Kepler also observed the planets in key points during the transits: they were basically caught at the right time at the moment of transit, always from our point of view, in front of their star. In this way, they measured the mass of the smallest planet with an accuracy of 3%.