Since the discovery of the first exoplanet in 1995, researchers have completed a vast scenario of planetary systems very different from our own. But only recently, thanks to the great precision of the Kepler space telescope , launched in 2009, it has been possible to detect rocky planets the size of the Earth and even quite smaller around stars similar to our Sun. Scientists from the Madrid Astrobiology Center (CAB ), associated with the NASA Astrobiology Institute, have just identified, for the first time, a planet smaller than Mercury .
For 978 days, Kepler recorded the transits of a star similar to our Sun , although smaller and cooler, called Kepler-37 (also known as KIC 8478994 and KOI-245) that indicated the existence of three exoplanets. The innermost of this system, as explained by CAB researcher David Barrado, “due to its extremely small size, similar to that of the Moon, and its highly irradiated surface, Kepler-37b is most likely a rocky planet without an atmosphere or water, similar to Mercury. “
In order to confirm that these were planets orbiting Kepler-37, radial velocities and variations in transit time did not work, so the researchers explored possible astrophysical scenarios – called blends or “false positives” – that could mimic the transit of a planet around Kepler-37 using specific and highly complex software called BLENDER.
Among other methods, an observational technique was used for the finding using data obtained with the Astralux instrument, installed in the 2.2-meter telescope of the Calar Alto Observatory (Almería), obtaining very high-resolution images of this star, of similar quality. to those that can be obtained with the Hubble Space Telescope.
In the words of Jorge Lillo-Box, a CAB researcher who has also participated in this work, “with the technique used, called lucky imaging , we have managed to rule out a large number of false positives, that is, we have eliminated configurations such as the presence of other stars or starspots. ” These phenomena can be confused with the presence of a planet, “since they cause similar effects on the data received, so only with a precise observation it is possible to rule out that they are stellar objects instead of planets,” he points out. Data collected by telescopes on the ground have also been necessary for the find . In the words of David Barrado, “without the additional observations from ground-based telescopes, it would not have been possible to adequately interpret the Kepler information.” “It is the most terrestrial space observatory binomial that produces the synergies required to produce this type of impressive discoveries, which a few years ago were beyond the wildest imagination,” he adds.
