A research team, including Bulgarian scientists, has identified three exoplanets in one of the most intriguing multi-planet systems discovered to date. This planetary system is located 1,100 light-years from Earth, orbiting the star TOI-4504 in the constellation Caelum.
The NASA TESS space telescope is recognized as one of the most effective tools for exoplanet detection. An exoplanet is defined as any planet that orbits a star outside our Solar System. TESS employs the transit method to search for these planets, allowing astronomers to estimate the size of the exoplanet and its orbital period—the time it takes to complete one orbit around its star. The gravitational influence of other exoplanets in the system can affect transit times, enabling scientists to discover new planets even if they do not transit their star.
This significant finding has been published in the prestigious journal Astrophysical Journal Letters, with key contributions from Bulgarian astronomer Dr. Trifon Trifonov, a researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, and an investigator in the Astronomy Department at Sofia University.
Dr. Trifonov leads the Bulgarian group searching for exoplanets within the EXO-RESTART project, supported by a contract with the National Science Fund.
Utilizing data from the TESS space telescope and observations from the FEROS spectrograph at the Max Planck Institute's 2.2-meter telescope in Chile, the team has confirmed the presence of three exoplanets in the TOI-4504 system. The closest, TOI-4504b, is approximately 2.5 times larger than Earth, while the other two, TOI-4504c and TOI-4504d, are classified as 'hot Jupiter' planets. With masses of 3.7 and 1.4 times that of Jupiter and orbital periods of 82.4 and 40.5 days, respectively, these gas giants are situated relatively close to their star.
Notably, observations reveal that TOI-4504c exhibits one of the largest cyclic variations in transit times—around four days. This is the most significant variation recorded among exoplanetary systems discovered to date, attributed to the gravitational pull of TOI-4504d on TOI-4504c, causing the latter to obscure its star's disk at varying times.
Lead author of the study, Michaela Vitkova, a doctoral candidate at the Czech Academy of Sciences, expressed surprise at the substantial variations observed in TOI-4504c's transit times. The amplitude of transit deviations during this observational period is about four days, significantly exceeding the previous record of half that amplitude.
The study of TOI-4504 is crucial for analyzing the evolution of similar exoplanetary systems. TOI-4504c and TOI-4504d are in a 2:1 orbital resonance, indicating they likely formed in a stable resonant configuration from the protoplanetary disk and subsequently migrated to their current orbits.
The team anticipates discovering exoplanets with similar or even greater variations in transit times in the future, which will further enrich astronomers' understanding of the formation of diverse planetary systems.
Dr. Rafael Bram from Adolfo Ibáñez University in Chile, a co-author of the study and coordinator of the WINE international consortium for hot Jupiter planet searches, emphasized the importance of collaborative efforts among scientists worldwide in achieving these goals.