Reference: Visit websiteA planet-size object that possibly once visited the solar system may have permanently changed our cosmic neighborhood by warping the orbits of the four outer planets, a new study suggests. The findings may shed light on why these planets' paths have certain peculiar features.
For decades, astronomers have debated how the solar system's planets formed . However, most hypotheses agree on the type of orbit the planets should have: circles that are arranged concentrically around the sun and lie on the same plane. (If you viewed them edge-on, you would see only a line.) However, none of the eight planets, including Earth, have perfectly circular orbits. Plus, the planets' paths don't lie precisely on the same plane.
Compared with Mercury (whose orbit, within our planetary family, is the most egg-shaped and tilted), the paths of the four outer giant planets ⁘ Jupiter, Saturn, Uranus and Neptune ⁘ show minor deviations from the ideal orbits. Yet explaining these niggling discrepancies has been challenging, said Renu Malhotra , a planetary scientist at the University of Arizona in Tucson and a co-author of the new study.
To tackle this puzzle, Malhotra and colleagues considered a less-examined scenario: that a visiting star-size object tweaked these planets' paths around 4 billion years ago.
Using computer models of the four outer planets, the team carried out 50,000 simulations of such flybys, each over 20 million years, while altering certain parameters of each visitor, including its mass, speed and how close it approached the sun. The researchers also expanded their search compared with previous studies by considering objects much smaller than stars ⁘ as tiny, in fact, as Jupiter . They also looked at situations with superclose passes, focusing on scenarios where the interloper came within 20 astronomical units (AU) of the sun. (One AU is approximately 93 million miles, or 150 million kilometers, roughly the average distance from Earth to the sun.)
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