Most of the information about Uranus was obtained when NASA’s robotic spacecraft Voyager 2 performed a five-day flyby in 1986.

In 1781, German-born British astronomer William Herschel made Uranus the first planet discovered with the help of a telescope. This cold planet, the third largest planet in our solar system, remains a mystery even after 243 years. And some of the things we thought we knew about it turned out to be wrong.

Most of the information about Uranus was obtained when NASA’s robotic spacecraft Voyager 2 performed a five-day flyby in 1986. However, scientists discovered that the probe was visited during a period of unusual conditions (an intense solar wind event) that led to misleading observations. About Uranus and especially its magnetic field.

The solar wind is a high-speed flow of charged particles emitted from the sun. Researchers took a new look at eight months of data from Voyager 2’s visit and found that it encountered Uranus just a few days after the solar wind compressed its magnetosphere (the planet’s protective magnetic bubble) to about 20%. usual volume.

“We found that the solar wind conditions present during the flyby occurred only 4% of the time. The flyby occurred during the peak of maximum solar wind intensity over the entire eight-month period,” said Jamie Jasinski, a space plasma physicist at NASA’s Jet Propulsion Laboratory. . opens new tab, said the lead author of the study published Monday in the journal Nature Astronomy.

“If Voyager 2 had arrived a week earlier, we would have observed a much larger magnetosphere,” Jasinski said. he said.

Such a visit could possibly show that Uranus’ magnetosphere is similar to that of the solar system’s other giant planets, Jupiter, Saturn and Neptune, the researchers said. The magnetosphere is the region of space surrounding a planet, dominated by the planet’s magnetic field, creating a protective zone against solar and cosmic particle radiation.

Voyager 2 observations left the false impression that Uranus’ magnetosphere is devoid of plasma and has unusually dense belts of high-energy electrons.

Plasma, the fourth state of matter after solids, liquids and gases, is a gas whose atoms are divided into high-energy subatomic particles. Because plasma is a common feature in the magnetospheres of other planets, its low concentration observed around Uranus was puzzling.

“The plasma environment of any planetary magnetosphere generally consists of plasma from the solar wind, plasma from any satellites located within the magnetosphere, and plasma from the planet’s atmosphere,” Jasinski said. he said.

“We did not see plasma from the solar wind or moons on Uranus. And the measured plasma was very faint,” Jasinski said. he said.

Blue-green in color due to methane in an atmosphere composed mostly of hydrogen and helium, Uranus is about 31,500 miles (50,700 km) in diameter. It is large enough to fit 63 Earths inside. Of the eight planets of the solar system, only Jupiter and Saturn are larger.

Its unusual tilt makes Uranus appear like a ball orbiting the sun. Orbiting almost 20 times farther from the Sun than Earth, Uranus has 28 known moons and two rings.

Voyager 2 observations had suggested that its two largest moons, Titania and Oberon, generally orbit outside the magnetosphere. The new study shows that they tend to remain within the protective bubble, making it easier for scientists to magnetically detect potential subsurface oceans.

“Both are thought to be prime candidates for hosting liquid water oceans in the Uranian system due to their large size relative to other large moons,” said Corey Cochrane, Jet Propulsion Laboratory planetary scientist and co-author of the study. he said.

Scientists are eager to learn whether the subsurface oceans on moons in the outer solar system have conditions suitable to support life. To answer this very question, NASA launched a spacecraft to Jupiter’s moon Europa on October 14.

“A future mission to Uranus is crucial to understanding not only the planet and its magnetosphere, but also its atmosphere, rings and moons,” Jasinski said. he said.