Astronomers find ’tilted’ planets even in pristine solar systems

Scientists have long wondered why all the planets in Earth’s solar system have slightly inclined orbits around the sun. But a new study led by Yale suggests that this phenomenon may not be so unusual after all. Even in “pristine” solar systems, the planets exhibit a slight tilt.

Astronomers have long assumed that planets with tilted, tilted orbits – orbits that do not align with the rotation axis of their host sun – are the result of a high-level cosmic hubbub, like nearby stars and planets moving around their neighbors.

But a new study published in The astronomical journal indicates the opposite.

For this study, an international research team led by Yale astronomer Malena Rice conducted a comprehensive analysis of pristine, multi-planetary solar systems, where the orbits of planets have remained relatively intact since their formation.

“This type of configuration, in which the orbit of one planet is precisely ordered with another in an exact integer ratio of orbital periods, is probably common in a solar system early in its development,” said Rice, assistant professor in astronomy at Yale School. of Arts and Sciences and lead author of the study.

“It’s a beautiful setup, but only a small percentage of systems keep it,” she said.

And even in these solar systems, Rice and his co-authors found, planets can have an orbital inclination of up to 20 degrees.

The researchers began their work by measuring the oblique orbit of TOI-2202 b, a “hot Jupiter” planet in a pristine solar system. A hot Jupiter is a planet much larger than Earth with an orbital period significantly shorter than Earth’s 365 days.

The researchers compared the orbit of TOI-2202 b with orbit data from the Comprehensive Census of similar planets found in NASA’s exoplanet archives. In this broader context, there was a typical tilt of up to 20 degrees for such planets, with the TOI-2202 b system being one of the most highly tilted such systems.

Rice said the discovery provides valuable information about the early development of the solar system and reveals something important about the Earth system: that a little bit of tilt is normal for the cosmic course.

“It’s reassuring,” Rice said. “This tells us that we’re not a super weird solar system. It’s really like we’re looking in a fun mirror and seeing how we fit into the larger picture of the universe.”

The new study also helps Rice in his research quest to understand Jupiter’s “hot” solar systems, which are systems containing gas giant planets that may be similar to Jupiter, but with very short orbital periods.

“I’m trying to understand why systems with hot Jupiters have such extremely inclined orbits,” Rice said. “When were they tilted? Can they just be born that way? To find out, I first need to find out what kinds of systems aren’t so radically tilted.”

The new study is the eighth result of the SOLES (Stellar Obliquities in Long-Permet Exoplanet Systems) investigation, founded by Rice and co-led with former Yale postdoctoral researcher Songhu Wang, who is now at the University of Indiana and co-author of the new study. Other co-authors include researchers from Belgium, Spain, Chile, Australia and the United States.