The moons that Uranus orbit are already known for unusual characteristics: some are very crratized, others have tectonic characteristics or a ridge patchwork and – -savaged cliff. Using the Hubble Space Telescope, the scientists took a look at the surface of the four largest moons in Uranus and discovered something rather unexpected.
For the study, a team of astronomers went to look for signs of interactions between the magnetic field of Uranus and its four largest moons: Ariel, Umbriel, Titania and Oberon. The moons, all called after characters from William Shakespeare, are all closed. This means that one side of the moon, the main side, always faces the planet, while the other, the final side, always looking at Uranus. Scientists had meant that the main side would be brighter, while the final side appeared darker. Instead, they found that it was the opposite, discovering clear evidence for the dimming of the main sides of the outer moons.
The findings, presented this week at the 246th Meeting of the American Astronomical Society, held in Anchorage, Alaska, indicate that the magnetosphere of Uranus could not interact much with their large moons, despite the previous data that suggest the opposite.
“Uranus is strange, so it has always been unsafe how much interacts the magnetic field with its satellites,” statement.
The ice giant is, in fact, a strange certificate. Uranus tilts 98 degrees, making it the only planet in the solar system with an equator almost at a right angle with its orbit. One day in Uranus is about 17 hours, the amount of time it takes to the planet to rotate on its axis. The planet completes an orbit around the Sun every 84 years of Earth. “At the time of the Voyager 2 Flyby (in 1986), the magnetosphere of Uranus leaned to about 59 degrees of the orbital plane of the satellites,” said Cartwright. “Therefore, there is an additional inclination in the magnetic field.”
Uranus and its magnetic field lines rotate faster than its moons orbiting the planet, causing the magnetic field lines to constantly drain ahead of the moons. As a result, scientists believed that the loaded particles of the magnetic field of the planet, or magnetosphere, should hit the surface of the rear sides of the moons. Those loaded particles would accumulate on the sides of the moons, dispersing radiation and, therefore, to make the darker appear on the side that moves away from Uranus.
Using Hubble Ultraviolet Capabilities, study scientists found that the leading and later hemispheres of Ariel and Umbriel are really very similar in brightness. For Titania and Oberon, it was the opposite of what they expected. The main hemispheres of the two outer moons were darker and reddrdder compared to their later hemispheres.
The team of scientists filed an explanation of the strange phenomenon. Uranus irregular moons, small distant bodies with eccentric orbits, are constantly struck by micrometeorites and expelling part of this material to the orbit around the planet. Throughout millions of years, this material moves to the orbits of Titania and Oberon.
As the moons orbits Uranus, they collect the dust “like insects that hit the car’s windshield while driving on a road,” according to a statement from the Space Telescope Science Institute. All this accumulation can be the one that causes titania and Oberon to appear darker and darker. “So this supports a different explanation,” Cartwright said. “This is the dust collection. I didn’t even expect to enter this hypothesis, but you know, the data always surprise you.”
As for the two other moons, Ariel and Umbriel, the magnetosphere of Uranus may interact with them, but not in a brilliant and dark side. The recent discovery adds more mystery to Uranus and its system.
