The discovery of a strange, wobbly planet has puzzled astronomers but could reveal the secrets of planet formation.
The new exoplanet, named TOI-1408 c, lies about 455 light-years from our solar system and orbits its star in a strange shimmying waltz with other planets, according to a new paper in The Astrophysical Journal Letters.
TOI-1408 c appears to vary in the time it takes to orbit its star, TOI-1408, and it also orbits another planet previously known to be around the star, a “hot Jupiter” named TOI-1408 b.
“The small planet shows unusual orbital behavior and shows a lot of variation in the time it passes the star, which is something we don’t see as a rule in planetary systems,” said study author Judith Korth, an astrophysicist at Sweden’s Lund University, in a statement.
The newly discovered planet is about eight times the mass of Earth and orbits a star very close to the previously discovered TOI-1408 b. The time it takes these two planets to orbit their star appears to be a 2:1 ratio, with the outer planet taking almost exactly twice as long to orbit as the newly discovered inner planet.
Astronomers can observe the planets from Earth by watching them cross in front of the star. But TOI-1408 c appears to vary in the time it takes between transits, known as transit time variation (TTV), as well as the length of time it takes to cross the star, or transit duration variation (TDV).
“The TTV amplitude for TOI-1408 c is about 15 percent of the planet’s orbital period, marking the largest TTV amplitude associated with an orbital period measured so far,” the researchers wrote in the paper.
The variation may arise due to the 2:1 orbital ratio with other planets, the researchers suggest.
“The planets are close to the 2:1 period commensurability with the librating resonance argument, but both remain outside the resonance configuration. This configuration leads to an extraordinary TTV and TDV, with TOI-1408 c showing the largest TTV amplitude relative to the recorded orbital period. away,” the researchers wrote.
Researchers also suggest that there may be a third planet in the system that has yet to be discovered and that could account for the variation in the timing and duration of transits.
“The dynamic nature of the system and the possibility of the presence of a third body invite further observational campaigns to refine the orbital parameters and investigate the long-term stability,” the researchers wrote.
He continued: “This study not only improves our understanding of the multiplanetary system involving hot Jupiter and its smaller companions, but also emphasizes the need for continued exploration to discover the various architectures of exoplanet systems.”
ESO/M. Kornmesser
The hope is that this discovery of how larger planets and smaller planets interact will help astronomers understand planet formation in more detail.
“Our results will help researchers learn more about how planets form and how they behave when they are very close, especially in systems with giant planets,” Korth said.
“We hope that our results can be used in future studies to find more planets in other systems, but also to better understand the various planetary systems that exist in our galaxy,” he said.
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Reference
Korth, J., Chaturvedi, P., Parviainen, H., Carleo, I., Endl, M., Guenther, EW, Nowak, G., Persson, CM, MacQueen, PJ, Mustill, AJ, Cabrera, J. , Cochran, WD, Lillo-Box, J., Hobbs, D., Murgas, F., Greklek-McKeon, M., Kellermann, H., Hébrard, G., Fukui, A., Winn, JN (2024) . TOI-1408: Discovery and Photodynamic Modeling of the Small Inner Companion to Hot Jupiter Revealed by Transit Time Variations. The Astrophysical Journal Letters, 971(2), L28. https://doi.org/10.3847/2041-8213/ad65fd
