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Chinese and Indian astronomers were the first to measure Earth\u2019s axial tilt accurately, and they did it about 3,000 years ago. Their measurements were remarkably accurate: in 1120 BC, Chinese astronomers pegged the Earth\u2019s axial tilt at 24 degrees. Now we know that all of the planets in the Solar System, with the exception of Mercury, have some tilt. <\/p>\n
While astronomers have puzzled over why our Solar System\u2019s planets are tilted, it turns out it\u2019s rather normal.<\/p>\n
<\/p>\n Now that astronomers have observed so many other solar systems, they\u2019ve learned that axial tilt is to be expected, even in so-called \u201cpristine\u201d solar systems. Pristine refers to the precise mathematical relationship between planets. <\/p>\n New research in The Astronomical Journal explains why some axial tilt is to be expected. It\u2019s titled \u201cEvidence for Low-level Dynamical Excitation in Near-resonant Exoplanet Systems.\u201d The lead author is Malena Rice, an assistant professor of astronomy at Yale\u2019s Faculty of Arts and Sciences.<\/p>\n The orbital resonance concept is at the heart of this research. <\/p>\n As planets orbit a star, they can exert regular and periodic gravitational influence on one another. When they do, astronomers say they\u2019re in resonance with one another. It also happens in moon systems around planets with many moons. Some resonant systems can be self-stabilizing, while others can become unstabilized over time. <\/p>\n \n