Bern/PlanetS: Two Planets Around a Red Dwarf

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Bern/PlanetS: Two Planets Around a Red Dwarf

Post by bystander » Fri Oct 16, 2020 2:39 pm

Two Planets Around a Red Dwarf
University of Bern | NCCR PlanetS | 2020 Oct 15
Size of TOI-1266 system compared to the inner solar system at a scale of one astronomical
unit, the distance between the Earth and the Sun. The orbital distances of the exoplanets
discovered around the star TOI-1266, which is half of the size of the Sun, are smaller than
Mercury’s orbital distance. TOI-1266 b, the closest planet to the star at a distance of 0.07
astronomical units, has a diameter of 2.37 times that of Earth’s and is therefore considered
a sub-Neptune. TOI-1266 c, at 0.01 astronomical units from its star and with 1.56 times the
Earth’s diameter, is considered a super-Earth. For each planetary system, the star’s diameter
and the orbital distances to its planets are shown in scale. The relative diameter of all
planets of both systems are on scale, being TOI-1266 b the largest planet and Mercury the
smallest. Credit: Juan Carlos Yustis (IA, UNAM)

The “SAINT-EX” Observatory, led by scientists from the National Centre of Competence in Research NCCR PlanetS of the University of Bern and the University of Geneva, has detected two exoplanets orbiting the star TOI-1266. The Mexico-based telescope thus demonstrates its high precision and takes an important step in the quest of finding potentially habitable worlds.

Red dwarfs are the coolest kind of star. As such, they potentially allow liquid water to exist on planets that are quite close to them. In the search for habitable worlds beyond the borders of our solar system, this is a big advantage: the distance between an exoplanet and its star is a crucial factor for its detection. The closer the two are, the higher the chance that astronomers can detect the planet from Earth. ...

Compared to the planets in our solar system, TOI-1266 b and c are much closer to their star – it takes them only 11 and 19 days respectively to orbit it. However, as their host star is much cooler than the Sun, their temperatures are not very extreme: the outer planet has approximately the temperature of Venus (although it is 7 times closer to its star than Venus is to the Sun).

The two planets are of similar density, possibly corresponding to a composition of about a half of rocky and metallic material and half water. This makes them about half as rocky as Earth or Venus but also far rockier than Uranus or Neptune.

In size, the planets clearly differ from each other. The inner planet, TOI-1266 b, measures up to a little under two-and-a-half times the Earth’s diameter. This makes it a so-called “sub-Neptune”. The outer planet, TOI-1266 c, is just over one-and-a-half times the size of our planet. Thus, it belongs to the category of “super-Earths”. ...

A Super-Earth and a Sub-Neptune Orbiting the Bright, Quiet M3 Dwarf TOI-1266 ~ Brice-Olivier Demory et al
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