An article published in “The Astronomical Journal” describes a research on the exoplanet K2-3d. This is a super-Earth discovered using the Kepler space telescope. An international team of researchers added more data collected later by the Spitzer space telescope and the Okayama Astrophysical Observatory’s telescope to get a more accurate measurement of this potentially habitable planet’s orbital period.
The exoplanet K2-3d is one of three super-Earths discovered in the system of the red dwarf K2-3, also known as EPIC 201367065, that is nearly 150 light years away from Earth. The star’s mass is about half that of the Sun so its light is much dimmer than the Sun’s. This means that on the planet K2-3d there could be conditions similar to those on the Earth even if it’s much closer to its star than the Earth to the Sun.
The other two super-Earths are even closer to their star than K2-3d so they receive from it a much more intense light than the Earth receives from the Sun. K2-3d is also the smallest of the three planets, with a radius estimated at around 1.6 times the Earth’s. Their discovery was announced in January 2015 among the first results of NASA’s Kepler space telescope’s second mission, called K2.
The discovery of the planet K2-3d was lucky not only for its interesting features but also because it’s one of the closest to the Earth and because its orbit is aligned with the Earth so we can see it pass in front of its star. This type of passage is one of the possible methods to discover and study exoplanets and in the case of the closest ones it makes them good candidates for follow-up research.
The image shows the elements of the research. An exoplanet passes in front of its star and the MuSCAT (Multi-colored Simultaneous Camera for studying Atmospheres of Transiting exoplanets) instrument mounted on Okayama Astrophysical Observatory’s 188 cm telescope captures the changes in its light.
The year of the planet K2-3d last just over 44 Earth days so it was possible to observe several of its transits. Two of them were observed with the Spitzer space telescope, shortly after the discovery, but the most interesting observations were made with the Okayama Astrophysical Observatory’s MuSCAT instrument. It allows specific multi-band analysis for the study of exoplanet transits and was used for follow-up observations of K2-3d showing that ground-based telescopes too can help this type of research.
Putting together the various observations, the astronomers improved the measurement of the planet K2-3d’s year. The Kepler space telescope provides limited observations of a single exoplanet and it’s for this reason that the measurements about their orbits are approximate. More observations are needed to improve them but thanks to instruments such as MuSCAT it’s now possible to accurately predict transits and plan new observations.
