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Discovery of Giant Exoplanet in Red Dwarf Star System Raises Formation Questions
The exploration of exoplanets has seen remarkable advancements in the past few years, with 5,799 confirmed planets in 4,310 star systems, and many more candidates under investigation. Among the most intriguing findings is the prolific formation of rocky planets around M-type red dwarf stars, which appear particularly adept at hosting diverse planetary systems.
Recent studies have highlighted the presence of gas giants and Super-Earths—planets several times the size of Earth—amongst these cooler, low-mass stars. A notable example is the red dwarf star TOI-6383A, which is revealed to host a giant planet, TOI-6383Ab, transiting in front of it. This planet is comparable in size and mass to its stellar companion, prompting new inquiries into how giant planets can form in such environments.
The research was spearheaded by Lia Marta Bernabò, a Ph.D. astronomy student at the University of Texas at Austin, collaborating with international experts from various institutions, including the German Aerospace Center. Their findings are detailed in a paper recently accepted by the Astronomical Journal and available on the arXiv preprint server.
Characteristics of the TOI-6383 System
The TOI-6383 system is located approximately 560 light-years from Earth and consists of two red dwarf stars. The primary star, TOI-6383A, has around 46% of the sun’s mass, while its companion, TOI-6383B, is even smaller at about 20.5% of solar mass. The surface temperatures of these stars are significantly lower than the sun’s, with TOI-6383A measuring approximately 3,444 K and TOI-6383B at about 3,121 K. The newly discovered exoplanet, TOI-6383Ab, boasts a mass and size similar to that of Jupiter and completes an orbit in roughly 1.79 days.
The GEMS (Searching for Giant Exoplanets around M-dwarf Stars) survey, which monitors stars for dips in brightness indicating potential transits, played a crucial role in the detection of TOI-6383Ab. NASA’s Transiting Exoplanet Survey Satellite (TESS) was instrumental in identifying this planet, followed by confirmation through ground-based telescopes employing photometric and radial velocity techniques.
Theories on Planet Formation
This latest discovery contributes significantly to the ongoing debate surrounding planet formation models. The core-accretion model suggests that planets form via the accumulation of smaller bodies around a solid core; however, this theory faces challenges when applied to M dwarf systems, which tend to have less material in their protoplanetary disks than larger stars. This discrepancy raises questions about the feasibility of forming giant planets in such environments.
Conversely, the rapid formation model proposes that planets may develop quickly from gravitational instabilities within massive disks, accumulating material in a shorter timeframe. The identification of a sizable planet like TOI-6383Ab around a low-mass star provides essential data to assess these competing hypotheses, as astronomers continue to investigate how formation dynamics may differ in differing stellar environments.
Currently, only 20 giant exoplanets have been confirmed around M-type red dwarfs. The GEMS survey aims to expand this catalog significantly, targeting at least 40 such discoveries to allow for improved testing and validation of planet formation theories.
More information: Lia Marta Bernabò et al., Searching for GEMS: TOI-6383Ab, a giant planet transiting an M3-dwarf star in a binary system, arXiv (2024). DOI: 10.48550/arxiv.2409.16889
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phys.org