Astronomers from the University of Liège have recently discovered two new exoplanets, one of which is super-Earth and the other is sub-Neptune.
The discovery was made with the help of the transiting satellite NASA for observation of exoplanets TESS and the HARPS-N high-resolution spectrograph. These instruments have helped astronomers measure the orbits, masses, and densities of exoplanets.
The exoplanets orbit the star TOI-1453 at a distance of 250 light years from Earth. The star itself is part of a binary star system in the constellation Draco. It is smaller than the Sun and colder than the Sun.
Types of exoplanets discovered are quite common in our galaxy, but there are no similar planets in the solar system. Scientists are most intrigued by the composition and properties of the atmosphere of these planets.
«These two planets present an interesting contrast in their characteristics. TOI-1453 b is a super-Earth, slightly larger than our planet and probably rocky. It completes a full rotation in just 4.3 days, making it a very close planet to its star. In contrast, TOI-1453 c is a sub-Neptune, about 2.2 times the size of Earth, but with an extremely low mass of only 2.9 Earth masses. This makes it one of the least dense subneptunes ever discovered, raising doubts about its composition»,— says astronomer Manu Stalport of the University of Liège.
To confirm the discovery, astronomers used 2 methods: transit, using TESS to measure the size and period of the planets’ rotation around the parent star, which caused a slight decrease in its brightness.
The second method involved measuring the radial velocity with a spectrograph HARPS-N, which allowed to observe the change in the velocity of the star TOI-1453 under the influence of the gravitational attraction of two exoplanets. This helped astronomers measure their mass and density.
«All of these observations showed that TOI-1453 c is extremely light for its size, suggesting that it may have a dense hydrogen-rich atmosphere or a water-dominated composition. This makes it an ideal candidate for future atmospheric studies. Understanding their formation and evolution could provide clues to the development of planetary systems, including our own», — Manu Stallport added.
At the same time, the rotation of both planets was close to a 3:2 resonance, when for every three rotations of the inner planet, the outer planet made almost two. Such resonances are considered to be a natural consequence of orbital migration, offering clues as to how the planets move and position themselves in their final orbits.
According to astronomers, modern telescopes such as the «James Webb» can provide scientists with the opportunity to analyze the atmosphere of TOI-1453 c in detail, determining the key composition of this sub-Neptune. This planet could have a hydrogen-rich atmosphere or contain water.
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The study was published in the journal Astronomy & Astrophysics
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