A super-Earth suitable for future atmospheric studies

The Institute of Astrophysics of Andalusia (IAA-CSIC) participates in the discovery of a planet around the red dwarf star Gliese 486, located only 26 light years away




Since the discovery of the first planet outside our Solar System in 1995, more than four thousand extrasolar planets have been detected. Now the challenge lies in detecting Earth-like planets and studying their atmospheres, an objective in which the CARMENES instrument, co-developed by the Institute of Astrophysics of Andalusia (IAA-CSIC) and installed in the Calar Alto Observatory (CAHA), is positioning itself as a leading instrument: tomorrow the discovery of a hot super-earth around a neighboring star will be published in the journal Science, whose proximity and characteristics make it the ideal candidate for atmospheric studies.

The planet, named Gliese 486b, is 2.8 times the mass of our planet and 30% larger. Its average density suggests that it is a rocky planet, like the Earth or Venus, and it revolves around its star in a circular orbit every 1.5 days at a distance of 2.5 million kilometres.



The planet revolves around the red dwarf star Gliese 486, much weaker and cooler than the Sun, but its proximity creates torrid conditions, with a minimum surface temperature of up to 430 degrees. Calculations made with existing models of planetary atmospheres point to the possibility that the planet retains a thin atmosphere, so that it would be an ideal candidate for atmospheric studies.

“The discovery of Gliese 486b has been a stroke of luck. If it had been a hundred degrees warmer, its entire surface would be lava and its atmosphere would consist of vaporized rocks, says José Antonio Caballero, a researcher at the Center for Astrobiology (CAB) and co-author of the study. On the other hand, if Gliese 486b was a hundred degrees cooler, it would not have been suitable for follow-up observations".

Future measurements by the CARMENES instrument team will try to determine the planet's orbital orientation, which makes it possible for Gliese 486b to pass in front of its star and produce a small eclipse. Each time this happens, known as a transit, a small fraction of the starlight would pass through, if any, the thin atmospheric layer of Gliese 486b before reaching Earth, which would allow the chemical composition of the atmosphere to be determined.

Measurements will also be made using a technique known as emission spectroscopy, possible when areas of the hemisphere illuminated by the star become visible as phases (similar to lunar, but planetary in this case) during the orbit of Gliese 486b until disappears behind the star. The spectrum obtained in this case contains information on the conditions of the hot and illuminated planetary surface.

CARMENES, whose consortium is made up of eleven research centers in Spain and Germany, will observe a set of 350 red dwarf stars in search of planets like the Earth. “CARMENES is really two instruments in one, observing simultaneously in the visible and in the infrared. This allows us, on the one hand, to carry out direct planet detections avoiding false positives and, on the other, to undertake the study of planetary atmospheres. The latter is possible thanks to the infrared channel (CARMENES-NIR), which was developed at the Institute of Astrophysics of Andalusia and which constitutes a worldwide reference in its field”, points out Pedro J. Amado, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) that has co-directed the development of CARMENES and that has participated in the discovery of Gliese 486b.

The discovery and characterization of Gliese 486b has been possible thanks to combined observations from CARMENES and other instruments on the ground, such as the Gemini North telescope or the Keck telescope, as well as from satellite, such as TESS. The research, headed by the Max Planck Institute of Astronomy (MPIA), has involved numerous Spanish researchers from the Astrobiology Center (CAB), the Space Sciences Institute (ICE-CSIC), the Canary Islands Institute of Astrophysics, the Institute of Astrophysics of Andalusia (IAA-CSIC) and the Calar Alto Observatory (CAHA).



T. Trifonov et al. A nearby transiting rocky exoplanet that is suitable for atmospheric investigation, Science 




Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación
Silbia López de Lacalle - sll[arroba]iaa.es - 958230676