In a new study, astronomers from Yale University and MIT examined the joint spin-orbit and orbit-orbit distribution for exoplanets residing in binary and triple-star systems.
An artist’s impression of a giant exoplanet and its two parent stars. Image credit: Sci.News.
A significant subset of all known exoplanet systems includes a host star with one or more bound stellar companions.
These multi-star systems can span a tremendous range of relative configurations, offering rich insights into the processes of star and planet formation.
“We show, for the first time, that there is an unexpected pile-up of systems where everything is aligned,” said Dr. Malena Rice, an astronomer at Yale University.
“The planets orbit precisely in the same direction that the first star rotates, and the second star orbits that system on the same plane as the planets.”
Dr. Rice and her colleagues used a variety of sources, including the Gaia DR3 catalogue of high-precision stellar astrometry, the NASA Exoplanet Archive’s Planetary Systems Composite Parameters table, and the TEPCat catalogue of exoplanet spin-orbit angle measurements, to create 3D geometries of planets in binary star systems.
The astronomers found that nine of the 40 systems they studied had ‘perfect’ alignment.
“It could be an indication that planetary systems like to push toward an orderly configuration,” Dr. Rice said.
“This is also good news for life forming in those systems.”
“Stellar companions that are aligned differently can wreak havoc on planetary systems, toppling them over or flash heating planets over time.”
“And just how would the world look on a more temperate Tatooine?”
“During some seasons of the year, it would be daytime continuously, with one star lighting up one side of the planet, while the other star was lighting the other half of the planet.”
“But that sunlight would not always be blazing hot, because one of the stars would be much farther away.”
“In other seasons of the year, both stars would light up the same side of the planet, with one star appearing much larger than the other.”
The study will be published in the Astronomical Journal.
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Malena Rice et al. 2024. The Orbital Geometries and Stellar Obliquities of Exoplanet-Hosting Multi-Star Systems. AJ, in press; arXiv: 2401.04173
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