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Here on Earth few people are familiar with the concept of planetary obliquity, but we all feel its effects: Obliquity measures a planet’s orbital tilt with respect to its star, which is what creates Earth’s changing seasons. Now, astronomers are proposing that shifts in obliquity could do even more.

According to new research published in Nature Astronomy, when a planet’s rotation and orbit line up just right, they can tip the world sufficiently askew to force it farther out or closer in to its star. The findings may help explain an almost decade-old mystery lurking in the thousands of worlds found by NASA’s planet-hunting Kepler space telescope.

As substantial as seasons may be to our lives, they have often been treated as scarcely more than rounding errors when considering the forces that shape an entire planet from core to crust to cloud top. That, combined with the fact it is presently very difficult to measure an exoplanet’s tilt, has led most astronomers to mostly ignore obliquity when they model the evolution of planetary systems. Yet in their study, co-authors Sarah Millholland and Greg Laughlin, both of Yale University, reveal obliquity-driven tides can have dramatic effects. “Large obliquities make stronger tides, and tides make the planet move,” Millholland says.

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Category: Science