Astronomers have made an unexpected discovery about the largest moons of Uranus. The “dark sides” of these icy satellites are not where scientists thought they would be. In fact, some are located on the opposite sides of the moons altogether.
Uranus has 28 confirmed moons, with five major ones: Miranda, Ariel, Umbriel, Titania, and Oberon. These moons are all named after characters from Shakespeare’s works. They range from 293 to 980 miles wide and are tidally locked to Uranus. This means the same half always faces the planet, much like Earth’s moon does.
Each moon has a “leading side,” which is always moving forward in its orbit, and a “trailing side,” which lags behind. Scientists expected the leading sides to be brighter in ultraviolet and infrared light. This is because they believed that electrons from Uranus’s magnetic field would accumulate on the trailing sides, making them darker.
However, a new study using the Hubble Space Telescope found surprising results. The leading sides of Ariel, Umbriel, Titania, and Oberon were not brighter; in fact, the trailing sides of Titania and Oberon were brighter than their leading sides. This contradicts previous theories.
The research team presented their findings at the 246th American Astronomical Society meeting in June. Although the results are not peer-reviewed yet, they have sparked interest in the scientific community.
Uranus is often described as a “weird” planet. Its axis is tilted by 98 degrees, making it look like it rolls through space rather than spinning like a top. This unusual tilt causes its moons to pass through Uranus’s magnetic field at awkward angles, complicating predictions about how that field interacts with the moons.
Dr. Richard Cartwright, a planetary scientist involved in the study, explained that the magnetic field’s behavior remains uncertain. Some researchers are even revisiting earlier data from the Voyager 2 probe, which made the first close measurements 40 years ago, as they consider the possibility that their assumptions about Uranus’s magnetosphere need to be updated.
The unexpected brightness of Titania’s and Oberon’s trailing sides points to a new idea called “dust shielding.” Researchers suggest that tiny bits of dust, formed from meteor strikes over millions of years, might be hitting the moons, affecting their brightness similar to how bugs hit a car’s windshield. This kind of material exchange has been observed in the systems of other planets like Jupiter and Saturn.
Interestingly, scientists also speculate that all four moons could support, or may have supported, subsurface oceans, much like Europa, Ganymede, and Enceladus do. This adds another layer of intrigue to their study.
The researchers are hopeful that the James Webb Space Telescope will help unlock more mysteries of Uranus and its moons. Already, it has provided valuable insights into the planet and its many secrets, paving the way for further exploration.