[ti:Scientists Identify Misunderstanding about Uranus]
[al:Science & Technology]
[ar:VOA]
[dt:2024-11-15]
[by:www.voase.cn]
[00:00.00]In 1781, German-born British astronomer William Herschel made Uranus the first planet discovered with a telescope. 
[00:13.37]But, 243 years later, we still do not know much about this cold planet, the third largest in our solar system.
[00:26.24]And some of what we thought we knew about it turns out to be untrue.
[00:33.89]Much of the knowledge about Uranus was collected when NASA's robotic spacecraft Voyager 2 flew past it in 1986. 
[00:46.48]But scientists have since learned that the craft visited at a time of unusual conditions. 
[00:55.30]An intense solar wind event at the time led to misleading observations about Uranus, and especially its magnetic field.
[01:08.25]The solar wind is a high-speed flow of charged particles coming from the sun.
[01:15.21]The researchers took a second look at eight months of data from around the time of Voyager 2's visit and found that it flew near Uranus just a few days after the solar wind had reduced the planet's magnetosphere to about 20 percent of its usual size.
[01:42.76]A magnetosphere is an area of space surrounding a planet that is controlled by the planet's magnetic field. 
[01:52.59]The magnetosphere protects the planet from solar and cosmic particle radiation.
[02:01.01]The Voyager 2 observations led scientists to think Uranus' magnetosphere lacked in plasma and had very intense belts of highly energetic electrons.
[02:17.01]Plasma is often called the fourth state of matter after solids, liquids and gases.
[02:26.46]In the night sky, plasma gives out light in the form of stars, nebulas, and even the auroras above the north and south poles.
[02:40.04]Plasma is a common feature in the magnetosphere of other planets, so scientists did not understand why there would not be much of it observed around Uranus.
[02:54.77]Jamie Jasinski studies space plasma at NASA's Jet Propulsion Laboratory.
[03:03.08]He is the lead writer of the study published recently in the publication Nature Astronomy.
[03:11.19]"We found that the solar wind conditions present during the flyby only occur 4 percent of the time.
[03:21.52]The flyby occurred during the maximum peak solar wind intensity in that entire eight-month period," Jasinski said.
[03:32.29]"We would have observed a much bigger magnetosphere if Voyager 2 had arrived a week earlier."
[03:41.41]Such a visit would likely have shown that the Uranus magnetosphere is like those of Jupiter, Saturn and Neptune, the solar system's other large planets, the researchers said.
[03:58.62]Uranus looks blue green because of the methane contained in its atmosphere. 
[04:05.97]The planet is big enough to fit 63 Earths inside it. 
[04:11.72]Among the solar system's eight planets, only Jupiter and Saturn are larger.
[04:19.61]Uranus orbits almost 20 times further from the sun than Earth does. 
[04:27.13]And it has 28 known moons and two sets of rings.
[04:33.75]Data collected by Voyager 2 had suggested that its two largest moons - Titania and Oberon - often orbit outside the magnetosphere. 
[04:46.47]But the new study shows that they usually stay inside the protective space, making it easier for scientists to magnetically detect possible subsurface oceans.
[05:02.68]"Both are thought to be prime candidates for hosting liquid water oceans in the Uranian system...," Jet Propulsion Laboratory planetary scientist and study co-writer Corey Cochrane said.
[05:19.11]Scientists want to learn whether subsurface oceans on moons in the outer solar system have conditions that could support life.
[05:31.36]So, on October 14, NASA launched a spacecraft on a mission to Jupiter's moon Europa to try to answer that question.
[05:43.25]"A future mission to Uranus is crucial to understanding not only the planet and magnetosphere, but also its atmosphere, rings and moons," Jasinski said.
[05:59.47]I'm Caty Weaver.