Red dwarfs are the coolest kind of stars. Thus, they potentially allow liquid water to exist on planets that are close enough to them. In the search for habitable worlds outside our solar system, this is a great advantage: the distance between the exoplanet and its star is a decisive factor in its detection. The closer the two are, the greater the chance that astronomers will be able to detect the planet from Earth.
“But these stars are quite small and emit little light compared to most other stars, such as our Sun,”; explains Bryce-Olivier Demori, lead author and professor of astrophysics at the University of Bern. These factors make them difficult to observe in detail. Without proper instruments, any planets that could orbit around them could easily be missed – especially terrestrial planets such as Earth, which are relatively small.
One of the tools with which you can carefully study the red dwarfs and their planets is the Mexican telescope SAINT-EX, which cooperates with NCCR PlanetS. SAINT-EX is an abbreviation that stands for search and characterization of transit exoplanets. The project is named after Antoine de Saint-Exupery (Saint-Ex), a famous writer, poet and aviator.
The SAINT-EX Observatory is a fully robotic institution with a 1-meter telescope. It is equipped with devices specifically suitable for high-precision detection of small planets orbiting steep stars. Now this specialization has paid off: earlier this year, the telescope was able to detect two exoplanets orbiting the star TOI-1266, located about 120 light years from Earth. A study published recently in a journal Astronomy and astrophysics, gives a first impression of their characteristics.
A kind of couple
Compared to the planets in our solar system, TOI-1266 b and c are much closer to their star – it takes only 11 and 19 days to orbit it. However, because their star is much cooler than the Sun, their temperatures are not very extreme: the outer planet is about the temperature of Venus (although it is 7 times closer to its star than Venus to the Sun). The two planets have the same density, possibly corresponding to about half of the rocky and metallic material and half of the water. This makes them about twice as bad as Earth or Venus, but also much worse than Uranus or Neptune.
The sizes of the planets are clearly different from each other. The inner planet, TOI-1266 b, measures about two and a half times the diameter of the Earth. This makes it a so-called “neptune”. The outer planet, TOI-1266 c, is slightly larger than the size of our planet. Thus, it belongs to the category of “super-earth”.
This places the two planets at the edges of the so-called radial valley, as Brice-Olivier Demore explains: “Planets between the radii TOI-1266 b and c are quite rare, probably due to the effect of strong radiation from a star that can blur their atmosphere.” Yilen Gomez Makeo Chu, SAINT-EX project coordinator and researcher at the National Autonomous University of Mexico, adds: “The ability to study two different types of planets in one system is a great opportunity to better understand how these different sized planets originate.”
Good deadlines and help from the embassy
Having this opportunity, especially this year, is anything but given. The scientists were fortunate to be able to complete their observations shortly before the COVID-19-related blockade in Mexico. Shortly after the observations were made, the observatory had to be closed due to the effects of the pandemic. This has not changed to this day. Scientists hope to resume SAINT-EX work in the next few months and target the next red dwarf and its potential planets. “In addition, the Mexican embassy in Bern has been a great help in facilitating discussions with the Mexican government and in continuing to support the project,” Demori said.
According to new estimates, there are up to six billion terrestrial planets in our galaxy
FOR. Demori et al., Aboveground and subneptune revolving around a bright, quiet dwarf M3 TOI-1266, Astronomy and astrophysics (2020). DOI: 10.1051 / 0004-6361 / 202038616
Provided by the University of Bern
Citation: Two planets found in the orbit of a red dwarf (2020, October 16), obtained on October 16, 2020 from https://phys.org/news/2020-10-planets-orbiting-red-dwarf.html
This document is subject to copyright. Except for any bona fide relationship for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.