![]() The large mass and angular momentum of the planet meant it was extremely unlikely that the planet's rotation would have decreased so noticeably.Īdding to the confusion, a later discovery by Cassini revealed that Saturn's northern and southern hemispheres were rotating at different speeds. Helled, who was not part of Karkoschka's research, studies the formation, evolution, and rotation of the planets.įifteen years after the Voyager flyby, Cassini's trip to Saturn revealed a complex magnetic field that had slowed down slightly. Nearly 34 years after their launch, the two probes continue to deliver key information as they journey out to the solar system's edge. NASA's Voyager 1 and Voyager 2 spacecraft were both launched in 1977 to study Jupiter, Saturn and their moons. "Voyager 2 only flew by Neptune, so its measurements are limited," Ravit Helled of Tel-Aviv University in Israel told in an email interview. But their information, which was originally used to calculate the rotation of the outer planets, was scanty. Karkoschka/The University of Arizona)Īs the Voyager 1 and Voyager 2 spacecraft flew past Saturn, Uranus, and Neptune in the 1980s, they captured radio signals produced by the gas giants' magnetic fields. By tracking features such as the Great Dark Spot and South Polar Feature, astronomers were able to refine measurements of the length of Neptune's day. The details of the study were published in the September edition of the journal Icarus.ĭifferent images emphasize the features on Neptune. "Now we have eight features that are locked together on one planet, and that is really exciting," Karkoschka said. "I thought the extraordinary regularity of Neptune's rotation indicated by the two features was something really special," Karkoschka said in a statement. In these images, Karkoschka found six additional features on Neptune that rotated with regularity. #NEPTUNES DAYS SERIES#He decided to widen his search to a series of more detailed images taken in 1989 by NASA's Voyager spacecraft. Two cloud formations, similar to Jupiter's famous Red Spot, stood out - the South Polar Feature and the South Polar Wave.Īfter studying the Hubble images, taken over a span of 20 years, Karkoschka determined that these distinct features appeared precisely on schedule. Karkoschka examined more than 500 images of Neptune that were taken by the Hubble Space Telescope. ![]()
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