The era of the detection of planets outside our Solar System, which began less than three decades ago, has ended to date with more than four thousand planets detected. Its astonishing variety has shown that the structure of our Solar System, with rocky planets in the inner regions and gaseous and icy outer regions, is not as typical as previously believed, and that other configurations seem more common, such as giant gas planets very close to their stars or systems with various super-Earths around dwarf stars. In this context, a new detection of two planetary systems by the CARMENES instrument, which operates at the Calar Alto Observatory (CAHA, Almería, Spain), reinforces the idea that dwarf stars tend to host rocky planets.
“Our current conception of the formation of low-mass planets in very close orbits to small stars suggests that they are very abundant, with an average of at least one planet per star. Despite this abundance, we hardly have data on the density of these planets that allows us to deduce their composition “, says Pedro J. Amado, researcher at the Institute of Astrophysics of Andalusia (IAA), attached to the Higher Council for Scientific Research (CSIC ) in Spain, and co-author of the new research.
In our Solar System, Earth, Mars, Mercury and Venus are classified as terrestrial or rocky planets. For extrasolar planets, those with between half and twice the size of the Earth are considered Earths, while those with up to ten times the mass of the Earth are classified as super Earths, terms that have no implications on the conditions. in surface or habitability. In fact, although the composition of terrestrial-type exoplanets could be similar to that of rocky planets in the Solar System, the composition of super-Earths can also encompass other combinations of gas, rock, ice or water.
The new systems detected are around the red dwarf stars (or M dwarfs) G 264-012 and Gl 393. Two planets with a minimum mass of 2.5 and 3.8 times that of the Earth have been found around the first. , which revolve around their star every 2.3 and 8.1 days. For its part, the planet of Gl 393 has a minimum mass of 1.7 Earth masses and revolves around its star every seven days. The three planets fall into the category of hot Earths and super-Earths, and reach temperatures that prevent the presence of liquid water on the surface.
The 3.5-meter telescope at the Calar Alto Observatory, from where the CARMENES instrument operates. (Photo: IAA)
“To understand how the different planetary systems that we are observing form and evolve we need robust statistics on the number of planets that exist, as well as information on the architecture of the systems and the density of the planets. Thus we will be able to explain those that do not fit into the known mechanisms, such as the GJ 3512 system that we also found with CARMENES and that presents a giant planet around a dwarf star, or confirm the tendency of dwarf stars to host multiple systems “, he indicates Pedro J. Amado.
In this sense, this work has also made it possible to detect a new factor that seems to influence the detections, since the planet around the star Gl 393 had gone unnoticed in previous campaigns with highly efficient planet-hunting instruments. Red dwarf stars show intense activity in the form of flares that can mask the signal from possible planets, and the research team warned that the failure to detect the planet of Gl 393 could be because previous observations were carried out during a peak. of activity. Thus, they concluded that planets can be more easily detected in dwarf stars with moderate activity or outside the maximums of the star’s activity cycle.
“The work of CARMENES is focused on expanding the data available to compose a global scenario about the planetary systems. The three planets in these two systems are among the smallest in mass, and therefore in the amplitude of the radial velocity that they instill in their stars, which shows the quality of the instrument ”, concludes Pedro J. Amado.
The study is titled “The CARMENES search for exoplanets around M dwarfs. Two terrestrial planets orbiting G264-012 and one terrestrial planet orbiting Gl393”. And it has been published in the academic journal Astronomy & Astrophysics. (Source: IAA)