Our latest simulations use over m particles, about , times more than most other studies today use. As well as making for some stunning pictures and animations of how the giant impact happened, this opens up all sorts of new science questions we can now begin to tackle.
These are basically lots of normal computers linked up together. So, running a big simulation quickly relies on dividing up the calculations between all parts of the supercomputer. SWIFT estimates how long each computing task in the simulation will take and tries to carefully share the work evenly for maximum efficiency. Just like a big new telescope, this jump to 1, times higher resolution reveals details we have never seen before.
As well as learning more about the specific history of Uranus, another important motivation is understanding planet formation more generally.
In recent years, we have discovered that the most common type of exoplanets planets that orbit stars other than our sun are quite similar to Uranus and Neptune. So everything we learn about the possible evolution of our own ice giants feeds in to our understanding of their far distant cousins and the evolution of potentially habitable worlds. One exciting detail we studied that is very relevant to the question of extraterrestrial life is the fate of an atmosphere after a giant impact.
Our high resolution simulations reveal that some of the atmosphere that survives the initial collision can still be removed by the subsequent violent bulging of the planet. The planet's poles are tilted 98 degrees and it spins clockwise. Astronomers have long wondered why the seventh planet's strange orientation doesn't match up with its planetary neighbors. One predominant theory believes that a giant object twice the size of Earth collided with the planet , knocking it off its vertical axis.
The problem with this theory is that an impact of that magnitude would have vaporized the ice on Uranus' moons, leaving an orbit filled with rocky husks, for which there is no evidence. Additionally, Uranus and Neptune have similar spin periods, which implies that they formed at roughly the same time.
But astronomers Zeeve Rogoszinski and Douglas Hamilton of the University of Maryland have come up with another hypothesis. Basically, when a planet's orbital precession, or shifts in its orbit around the sun, matches up with its rotational precession, or how much the planet wobbles when rotating, it begins to tilt. Uranus owes its vibrant blue-green hues not from unusual oceans but from an upper atmosphere flush with methane , which absorbs the sun's red light and scatters blue light back to our eyes.
The rest of planet's atmosphere is largely made of hydrogen and helium, with scant amounts of ammonia, water, and methane. Trace amounts of hydrogen sulfide also hint that, if you could visit this distant place without a spacesuit, the planet would smell like rotten eggs.
While Saturn wears the crown for the least dense planet in our celestial family, Uranus is not far behind: Most of its mass is made up of an icy dense fluid of water, ammonia, and methane. One particularly curious feature of Uranus is its off-kilter positioning. The gas giant is tipped on its side, spinning on its axis at nearly a right angle to its orbital path around the sun, which requires a lengthy 84 Earth-years to complete.
Scientists believe that this unexpected tilt is the result of a massive collision with something the size of Earth far in the planet's past. Thanks to its sideways turn, Uranus has some wild seasons, with the sun blazing across each pole for 21 Earth-years at a time while the opposing side lingers in the pitch blackness of space. And that's not the only strange thing about its spin. Like Venus, Uranus has what's known as a retrograde rotation, turning on its axis in the opposite direction to the rest of the planets.
Also topsy turvy is Uranus' magnetosphere, the magnetic field enveloping the gaseous world. It's tipped nearly 60 degrees from the axis of rotation. That sets the planet's auroras out of line, making them appear far from the poles, unlike those on Earth. The first planet found with the aid of a telescope, Uranus was discovered in by astronomer William Herschel. The seventh planet from the sun is so distant that it takes 84 years to complete one orbit.
Only one spacecraft, Voyager 2, has ever flown by Uranus at close range. The craft came as near as 50, miles to Uranus' cloud tops in , giving scientists their first detailed peek at both the planet and its many curious moons.
During that encounter, Voyager 2 snapped what is perhaps the most famous picture of Uranus—a pale turquoise orb in a sea of darkness. But follow-up observations have since shown that there's more there than initially meets the eye. No other planet in the solar system is tilted as much — Jupiter is tilted by about 3 degrees, for example, and Earth by about 23 degrees. Now, researchers in Japan suggest a giant cosmic impact may not only have knocked Uranus on its side, but also created most of the planet's moons.
Uranus possesses 27 known moons. Eighteen of these moons orbit around the planet's equator, and these "regular" moons make up 98 percent of the total mass of Uranus' moons , said study lead author Yuya Ishizawa at Kyoto University in Japan.
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