Researchers reveal a magnetic misconception regarding Uranus
In 1781, German-born British astronomer William Herschel became the first to discover Uranus using a telescope. This cold planet, the third largest in our solar system, still holds many mysteries 243 years later. Additionally, some of our previous understandings about it have proven to be inaccurate.
TroibNews 
In 1781, German-born British astronomer William Herschel became the first to discover a planet with a telescope, uncovering Uranus. Nearly 243 years later, this cold planet, the third largest in our solar system, continues to baffle scientists, and some previous understandings have proven inaccurate.
Much of what we know about Uranus comes from NASA's Voyager 2, which conducted a five-day flyby in 1986. Recent studies have revealed that the probe's visit occurred during an unprecedented solar wind event, leading to skewed observations about the planet, particularly concerning its magnetic field.
The solar wind, a high-speed stream of charged particles released by the sun, impacted the findings from Voyager 2. A thorough analysis of eight months of data surrounding the spacecraft’s visit demonstrated that it arrived just days after the solar wind compressed Uranus’s magnetosphere—its protective magnetic bubble—to about 20 percent of its typical size.
"We found that the solar wind conditions present during the flyby only occur 4 percent of the time. The flyby occurred during the maximum peak solar wind intensity in that entire eight-month period," explained Jamie Jasinski, a space plasma physicist at NASA's Jet Propulsion Laboratory and lead author of a study published in Nature Astronomy.
"We would have observed a much bigger magnetosphere if Voyager 2 had arrived a week earlier," Jasinski added.
Had the probe visited a week earlier, it is likely that it would have revealed a magnetosphere more akin to those of Jupiter, Saturn, and Neptune—the other giant planets of the solar system. A magnetosphere denotes the space surrounding a planet dominated by its magnetic field, which protects against solar and cosmic radiation.
The observations made during the Voyager 2 flyby led to a misconception that Uranus's magnetosphere lacked plasma and had exceptionally strong electron belts. Plasma, the fourth state of matter, consists of gas particles that have become high-energy subatomic particles. Unlike other planets' magnetospheres, the low plasma concentration surrounding Uranus puzzled researchers.
"The plasma environment of any planetary magnetosphere is usually formed of plasma from the solar wind, plasma from any moons present inside the magnetosphere, and plasma from the atmosphere of the planet," Jasinski noted.
"At Uranus, we did not see plasma from the solar wind or from the moons. And the plasma that was measured was very tenuous," he added.
Uranus features a blue-green hue, deriving its color from methane in an atmosphere primarily composed of hydrogen and helium, and boasts a diameter of approximately 50,700 km—large enough to encompass 63 Earths. Among the eight planets in the solar system, only Jupiter and Saturn are larger.
The planet's distinctive tilt causes it to orbit the sun in a manner reminiscent of a rolling ball. Orbiting nearly 20 times farther from the sun than Earth, Uranus has 28 known moons and two ring systems.
Previous Voyager 2 data suggested that Uranus's two largest moons—Titania and Oberon—typically orbit outside its magnetosphere. However, the new study indicates that these moons likely remain within the protective magnetic bubble, thereby simplifying the process for scientists attempting to 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 the other major moons," stated Corey Cochrane, a planetary scientist at Jet Propulsion Laboratory and co-author of the study.
Researchers are keenly interested in whether subsurface oceans on moons in the outer solar system possess conditions that could support life. In relation to this, NASA recently launched a spacecraft on October 14 aimed at investigating the habitability of Jupiter's moon Europa.
"A future mission to Uranus is crucial to understanding not only the planet and magnetosphere, but also its atmosphere, rings, and moons," emphasized Jasinski.
Camille Lefevre for TROIB News
Much of what we know about Uranus comes from NASA's Voyager 2, which conducted a five-day flyby in 1986. Recent studies have revealed that the probe's visit occurred during an unprecedented solar wind event, leading to skewed observations about the planet, particularly concerning its magnetic field.
The solar wind, a high-speed stream of charged particles released by the sun, impacted the findings from Voyager 2. A thorough analysis of eight months of data surrounding the spacecraft’s visit demonstrated that it arrived just days after the solar wind compressed Uranus’s magnetosphere—its protective magnetic bubble—to about 20 percent of its typical size.
"We found that the solar wind conditions present during the flyby only occur 4 percent of the time. The flyby occurred during the maximum peak solar wind intensity in that entire eight-month period," explained Jamie Jasinski, a space plasma physicist at NASA's Jet Propulsion Laboratory and lead author of a study published in Nature Astronomy.
"We would have observed a much bigger magnetosphere if Voyager 2 had arrived a week earlier," Jasinski added.
Had the probe visited a week earlier, it is likely that it would have revealed a magnetosphere more akin to those of Jupiter, Saturn, and Neptune—the other giant planets of the solar system. A magnetosphere denotes the space surrounding a planet dominated by its magnetic field, which protects against solar and cosmic radiation.
The observations made during the Voyager 2 flyby led to a misconception that Uranus's magnetosphere lacked plasma and had exceptionally strong electron belts. Plasma, the fourth state of matter, consists of gas particles that have become high-energy subatomic particles. Unlike other planets' magnetospheres, the low plasma concentration surrounding Uranus puzzled researchers.
"The plasma environment of any planetary magnetosphere is usually formed of plasma from the solar wind, plasma from any moons present inside the magnetosphere, and plasma from the atmosphere of the planet," Jasinski noted.
"At Uranus, we did not see plasma from the solar wind or from the moons. And the plasma that was measured was very tenuous," he added.
Uranus features a blue-green hue, deriving its color from methane in an atmosphere primarily composed of hydrogen and helium, and boasts a diameter of approximately 50,700 km—large enough to encompass 63 Earths. Among the eight planets in the solar system, only Jupiter and Saturn are larger.
The planet's distinctive tilt causes it to orbit the sun in a manner reminiscent of a rolling ball. Orbiting nearly 20 times farther from the sun than Earth, Uranus has 28 known moons and two ring systems.
Previous Voyager 2 data suggested that Uranus's two largest moons—Titania and Oberon—typically orbit outside its magnetosphere. However, the new study indicates that these moons likely remain within the protective magnetic bubble, thereby simplifying the process for scientists attempting to 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 the other major moons," stated Corey Cochrane, a planetary scientist at Jet Propulsion Laboratory and co-author of the study.
Researchers are keenly interested in whether subsurface oceans on moons in the outer solar system possess conditions that could support life. In relation to this, NASA recently launched a spacecraft on October 14 aimed at investigating the habitability of Jupiter's moon Europa.
"A future mission to Uranus is crucial to understanding not only the planet and magnetosphere, but also its atmosphere, rings, and moons," emphasized Jasinski.
Camille Lefevre for TROIB News
