By Antonio Manaytay
The Mexico-based SAINT-EX has detected two planets orbiting a red dwarf star some 120 light years away from the Earth.
In a study published in Astronomy and Astrophysics, Brice-Olivier Demory said red dwarf stars are the coolest type of star emitting small amount of light. Demory, a University of Bern professor, is the lead author of the study.
This characteristic, he said, allows water to exist in the planets near them. But to detect the planets orbiting them is difficult because their size is small.
SAINT-EX Observatory, a robotic facility that hosts a one-meter telescope, had just did that when it detected two, not one, planets orbiting TOI-1266, a dwarf star. SAINT-EX is Search And CharacterIsatioN of Transiting EXoplanets, named in honor of Antoine de Saint-Exupéry (Saint-Ex).
The observatory specializes in high-precision detection of the possible existence of small exoplanets around dwarf stars.
TOI-1266 b and c
Unlike the planets in the solar system, the two planets, TOI-1266 b and c stay closer to their parent star. It takes 11 days for planet b to orbit the star while planet c orbits for 19 days.
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But the temperatures of these planets are not very high despite their distance from TOI-1266. Planet c, for instance, has the temperature of Venus. This despite its distance to the star is seven times nearer than Venus to the sun.
These two exoplanets have the same density, which suggests a half water and rocky or metallic composition. It is possible they are half rocky as the Earth but more rocky than Neptune or Uranus.
In terms of size, the two planets variably differ.
Planet b is two-and-a-half times smaller than the diameter of the Earth while planet c is one-and-a-half times of the Earth’s size. It is apt to call the former a “sub-Neptune” while the latter fits well to the “super-Earths” category.
These planets, Demory said, are at the edges of radius-valley. The radius-valley refers to the rarity of planets with radiuses between 1.5 and 2 times the radius of the Earth due to evaporation because of their proximity to the star.
Planets with the radius of TOI-1266 b and c are rare “because of the effect of strong irradiation from the star, which can erode their atmospheres,” Demory explained.
Their detection alone is a feat by itself.
As SAINT-EX project coordinator Yilen Gómez Maqueo Chew, researcher at the National Autonomous University of Mexico has pointed out, “It is great opportunity to better understand how these two different sized planets come to be.”