Astronomers have discovered that a planetary system previously thought to have no planets actually consists of two planets that orbit their star in a unique way, resembling an old-fashioned carousel. This is the first time such a system has been identified, and existing planetary formation theories cannot explain how it came to be.
The United States National Aeronautics and Space Administration (NASA) revealed that astronomers observed the KOI-134 system more than 10 years ago using the agency’s Kepler Space Telescope. KOI-134 is a star located 3,500 light-years away from Earth.
Initially, astronomers believed there was a single planet orbiting KOI-134, but its transit (the passage in front of the star) was so anomalous that this planet was dismissed before further analysis could be conducted.
Subsequently, an international research team led by the University of Southern Queensland in Australia reanalyzed the Kepler Space Telescope’s observations and confirmed the existence of two planets in the KOI-134 system—KOI-134 b and KOI-134 c. These planets orbit the star in distinct ways on two different orbital planes, with one planet exhibiting a significant difference in transit timing.
They found that the transit timing of KOI-134 b could be “late” or “early” by up to 20 hours, a substantial difference. This significant difference prevented the initial confirmation of the planet during the first observations.
The researchers explained that the transit timing discrepancy of KOI-134 b is caused by its gravitational interaction with the other planet, KOI-134 c. KOI-134 b, a gas giant similar in size to Jupiter, is farther from the star, while KOI-134 c, slightly smaller than Saturn, is closer.
KOI-134 c had not been observed before because its orbital plane differs from that of KOI-134 b, and its orbit is inclined, preventing transits. The orbital planes of these two planets are inclined about 15 degrees from each other. Due to their gravitational interactions, their orbital planes tilt back and forth.
Another intriguing feature of this planetary system is orbital resonance. The resonance ratio between these two planets is 2:1, meaning that as one planet completes one orbit, the other planet completes two orbits.
In this scenario, the orbital period of KOI-134 b is approximately 67 days, while that of KOI-134 c ranges from 33 to 34 days, with the former being twice the latter.
Due to the effects of inclined orbits, transit timing differences, and orbital resonance, the trajectories of these two planets orbiting the star resemble two wooden horses moving up and down on an old-fashioned carousel.
Emma Nabbie, a doctoral student at the University of Southern Queensland who led the research, stated that this discovery challenges long-standing theories about planetary formation.
She likened the rhythmic interconnected orbits of these two planets – moving apart and slowly reuniting – to a cosmic dance on the celestial stage.
She remarked, “This is the first time a system with such strong gravitational interactions and misaligned orbits has been observed – posing a significant challenge to planetary formation theories because there is currently no theory that can explain how such a system was formed.”
The findings of this research were published on June 27 in the journal “Nature Astronomy.”