Free Astronomy Magazine January-February 2019

11 JANUARY-FEBRUARY 2019 around low-mass stars, a sce- nario which gives credibility to the results of the Ribas team. It is interesting to note that current theories of planetary formation predict that the snow-line is the most favorable distance for the birth of super-Earths. Discovering one of these planets in the orbit within which it most likely formed, and in such a mature star system, could question some aspects of planetary migra- tion theories, which disadvan- tage the maintenance of a planet within its original or- bit. It is, however, possible that Barnard’s Star b has not migrated because not per- turbed in its orbital motion either by the residual dust of the protoplanetary disk or by other orbiting plan- ets. This does not ex- clude, in any way, that another planet may exist much farther away in this system, whose pres- ence could be associated with the long-term mod- ulation mentioned above. With reference to this possibility, the article pub- lished by the research team last November in Nature suggested the existence of a second planet with a mini- mum mass equal to 15 Earth masses in orbit at 4 AU from the star, but the existence of this second planet is just a hypothesis. On the contrary, the existence of Barnard’s Star b is almost certain, which becomes the second exoplanet closest to us after Proxima Centauri b (which is more “similar” to the Earth). When the technology is mature enough to send probes to the nearest planetary sys- tems, Barnard’s Star b will be one of the first destinations; in the meantime, we will cer- tainly be able to photograph it directly and to characterize it with sufficient precision. If it travels through the expected orbit, it should move away 220 milliarcseconds from its star, a sufficient angular distance to make it visible in the most powerful telescopes that will be available to astronomers in the imminent future. Although there is no hope of revealing biomarkers in its atmosphere, the direct study of Barnard’s Star b will allow us to better understand a type of planet that, although common in the galaxy, is not present in our own Solar System. A n artistic vision of Barnard’s Star b, lit by the red light of the star. [IEEC/ Science-Wave – Guillem Ramisa] !