The six planets in the HD 110067 system orbit in a regular pattern due to each other’s gravitational influence.
Thibault Roger/NCCR PlanetS (CC BY-NC-SA 4.0)
A group of six ancient exoplanets whose orbits have not changed in billions of years could tell us how planetary systems like our solar system formed.
When planets orbit a star in a certain regular pattern, they are said to be in resonance. It remains in this state until another large object passing nearby or a collision knocks it off course, causing it to enter a chaotic and changing orbit. For example, Jupiter and Saturn are thought to have swapped positions as they passed nearby early in the formation of our solar system.
“When chaotic movements occur within a system, information about its initial state is lost. It is not possible to trace where the planet has been in the past.” Rafael Luque at the University of Chicago. But without this chaotic movement, he says, the resonant system would remain unchanged from its birth.
In 2020, astronomers used the Transiting Exoplanet Survey Satellite (TESS) to discover a pair of resonant planets around the star HD 110067, about 100 light-years away. But Luque and his colleagues noticed other signals in the data that didn’t make sense. They followed up on this observation several years later using TESS and the Space-based Characterization ExOPlanet satellite (CHEOPS) and discovered a third planet, but the signal was still not fully explained. .
The research team looked at simulations of the signals generated by different combinations of resonant planets. For example, a planet orbits a star three times in the time it takes another planet to orbit twice. This revealed a system containing her six planets orbiting in a plane, an almost perfect match to the data.
“It is truly an amazing feat that the system resonates so perfectly,” Luque says. “If we take a mathematical solution, we can predict the period.” [how long the planets take to orbit the star] At exactly the right time we actually see it. ”
This perfect resonance means that the planet HD 110067 has likely been this way since it formed 4 billion years ago. “When you look back, it’s like a fossil,” he says. sean raymond at the University of Bordeaux, France. “In this type of system, there’s not much change from the gas phase, so we can investigate certain aspects of it.”
All of these planets have orbits shorter than 50 days, making them classified as “mini-Neptunes,” the smallest gas planets in our solar system, but astronomers don’t fully understand it. .
Because HD 110067 is so bright compared to other stars we know of as hosts to mini-Neptunes, follow-up observations by telescopes like the James Webb Space Telescope have revealed much about these planets and how they formed. You should be able to gather information. “This is actually his one percent of his one percent of exoplanet systems,” Luque says.
In addition to learning about the history of the planet, we will also be able to learn about the conditions of the planet’s atmosphere and interior. Three of the planets appear to have relatively low densities, which suggests they may contain water, making them potentially habitable, Luque said. added.
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