As proof that first impressions can be misleading, one need not look further than Uranus. After the spacecraft Voyager 2 visited Uranus in 1986, it was dubbed “the most boring planet” in the Solar System. But recent photos from the Hubble Telescope reveal that Uranus is not as dull as once imagined.
For one thing, Uranus is the only planet other than Venus with a retrograde (i.e., clockwise) orbit. Unlike the other planets of the solar system, however, Uranus is tilted almost all the way over on its axis. Essentially, it orbits the sun on its side. Astronomers hypothesize that this unusual orientation might be due to a collision with a planet-sized body soon after Uranus was formed.
Because of its unusual axial tilt, each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness. (A year on Uranus is equal to 84 years on Earth). Bizarrely, however, even though the poles receive more sun than the equator, Uranus is – for unknown reasons — hotter at its equator than at its poles.
Uranus’ extreme axial tilt can give rise to unusual weather. As sunlight reaches the areas that have been dark for so long, the atmosphere heats up, triggering gigantic springtime storms roughly the size of North America.
Uranus’ magnetic field is also odd in that it, too, is tipped over– nearly 60 degrees from the planet’s axis of rotation. This has resulted in a lopsided magnetic field, whose strength at the surface of the “northern hemisphere” is more than 10 times that at the southern.
On a clear night, Uranus is just visible to the naked eye. Methane in Uranus’ upper atmosphere absorbs red light, making the planet appear a uniform blue. Like the other gas giants in our Solar System, however, Uranus actually has rings — 13 discovered thus far. While the inner set of rings is narrow and dark, two rings farther from the planet’s surface are brightly colored — one red and one blue.
Uranus is the only planet named directly for a Greek deity, rather than a Roman one. Ouranos was the ancient Greek deity of the Heavens, as well as the father of Cronus (Saturn), the Cyclops and the Titans.
Uranus is also the only planet with moons that aren’t named for figures from Greek or Roman mythology. The largest of its 27 known moons are, instead, named for characters from the works of William Shakespeare and Alexander Pope.
At 1,787,000,000 miles from the sun, Uranus remains largely a mystery. But of one thing we can be certain – whatever we learn about this not-so-gentle giant won’t be dull.