Uranus is arguably the most mysterious planet in the solar system – we know very little about it. So far, we have only visited the planet once, with the Voyager 2 spacecraft back in 1986. The most obvious odd thing about this ice giant is the fact that it is spinning on its side.
Unlike all the other planets, which is roughly upright with their spin axes, Uranus is tilted by almost a right angle. So in its summer, the north pole points almost directly towards the sun. And unlike Saturn, Jupiter, and Neptune, Uranus has vertical rings and moons that orbit around its tilted equator.
The ice giant also has a surprisingly cold temperature and a magnetic field, unlike the neat bar magnet shape of Earth or Jupiter. Scientists therefore suspect that Uranus was once similar to the other planets in the solar system but was suddenly flipped over. So what happened? Our new research, published in the Astrophysical Journal and presented at a meeting of the American Geophysical Union, offers a clue.
Violent place, with protoplanets colliding in violent giants. Most researchers believe that Uranus' spin is the consequence of a dramatic collision. We set out to uncover how it could have happened.
We wanted to study giant impacts on Uranus to see exactly how a collision could have affected the planet's evolution. Unfortunately, we can not (yet) build two planets in a lab and smash them together to see what happens. Instead, we run computer models simulating the events using a powerful supercomputer as the next best thing.
The basic idea was to model the colliding planets with millions of particles in the computer, each representing a lump of planetary material. So they can collapse into each other. This way we can study even the fantastically complicated and messy results of a giant impact. Another benefit of using computer simulations is that we have full control. We can test a wide variety of different impact scenarios and explore the range of possible outcomes.
Uranus has today by slamming and merging with a young planet. For more grazing collisions, the impacting body's material would probably end up spreading out in a thin, hot shell near the edge of Uranus's ice layer, underneath the hydrogen and helium atmosphere.
This could inhibit the mixing of material inside Uranus, trapping the heat from its formation deep inside. Uranus' exterior is so cold today. Thermal evolution is very complicated, but it is at least clear how a giant impact can reshape a planet both inside and out.
The research is exciting from a computational perspective. Like the size of a telescope, the number of particles in a simulation limits. However, it just takes a long time to make it on a powerful computer.
Our latest simulation uses over 100m particles, about 100-1,000 times more than most other studies today. As we are now doing, there are a lot of new and exciting things that are going on in the world of science.
This improvement is thanks to SWIFT, a new simulation code designed to take full advantage of contemporary "supercomputers". 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 takes in the simulation. Just like a big new telescope, we have never seen before.
Exoplanets and beyond
As well as learning more about the specific history of Uranus. 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 potential evolution of potentially habitable worlds.
Uranus seen by Voyager 2. NASA / JPL-CaltechOne exciting detail that is very relevant to the question of extraterrestrial life is the fate of an atmosphere after a giant impact. Violent bulging of the planet.
The lack of an atmosphere makes a planet less likely to host life. Then again, perhaps the massive energy input and added material might help create the useful chemicals for life as well. Rocky material from the impacting body's core can thus be mixed into the outer atmosphere. This means we can look at them at an exoplanet's atmosphere.
Lots of questions remain about Uranus, and giant impacts in general. Even though our simulations are getting more detailed, we still have lots to learn. Many people are calling for a new mission to Uranus and Neptune to study their strange magnetic fields, their quirky families of moons and even simply and simply what they actually made of.
I would like to see that happen. Uranus, but the myriad planets that fill our universe and how they came to be.
This article is republished from The Conversation by Jacob Kegerreis, PhD Student, Computational Astronomy, Durham University under a Creative Commons license. Read the original article.