Using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and several ground-based telescopes, astronomers have discovered and validated a two-planet system — composed of a super-Earth and a mini-Neptune — around the mid-type M dwarf star TOI-2096.
TOI-2096 is located around 48 parsecs (156.5 light-years) away in the constellation of Draco.
Otherwise known as TIC 142748283, the star hosts two massive exoplanets.
The inner planet is a so-called super-Earth approximately 1.2 times larger than Earth.
The outer world is a mini-Neptune about 1.9 times larger than our planet.
Named TOI-2096b and TOI-2096c, respectively, the planets likely reside in slightly eccentric orbits.
“Making an exhaustive analysis of the data, we found that the two planets were in resonant orbits: for each orbit of the outer planet, the inner planet orbits the star twice,” said Mathilde Timmermans, a doctoral student at the Université de Liège.
“Their periods are therefore very close to being a multiple of each other with about 3.12 days for TOI-2096b and about 6.38 days for TOI-2096c.”
“This is a very particular configuration, and it causes a strong gravitational interaction between the planets.”
“This interaction delays or accelerates the passage of the planets in front of their star and could lead to the measurement of the planetary masses using larger telescopes in the near future.”
While the size of planet TOI-2096b is compatible with a rocky composition, TOI-2096c is located in a particular parameter space where different formation models yield different predictions for its composition.
“These planets are of crucial importance given their sizes,” Timmermans said.
“The formation of super-Earths and mini-Neptunes remains a mystery today.”
“There are several formation models trying to explain it, but none fits the observations perfectly.”
“TOI-2096 is the only system found to date that has a super-Earth and a mini-Neptune precisely at the sizes where the models contradict each other.”
“In other words, TOI-2096 may be the system we’ve been looking for to understand how these planetary systems have formed.”
“We also found that in their class, TOI-2096 planets are ideal for atmospheric studies,” the astronomers said.
“In particular, using NIRSpec/Prism on board the NASA/ESA/CSA James Webb Space Telescope, only a few candidates are better suited, such as the LP 791-18c, and TRAPPIST-1 planets.”
“In the context of ESA’s future Ariel mission, while the planets are not among the best to be studied using the ArielRad, they lie in a region of the parameter space poorly populated, keeping the door open to be included in dedicated surveys for small planets in multiplanetary systems.”
“These characteristics make the TOI-2096 system appealing for further analyses and studies in various disciplines, such as planetary formation and evolution, multiplanet dynamics, interior modeling, planet-planet and star-planet interactions, comparative planetology, and atmospheric characterization.”
The team’s paper was published in the journal Astronomy & Astrophysics.
F.J. Pozuelos et al. 2023. A super-Earth and a mini-Neptune near the 2:1 MMR straddling the radius valley around the nearby mid-M dwarf TOI-2096. A&A 672, A70; doi: 10.1051/0004-6361/202245440