The gas and ice giant Uranus was for a long time a source of the mystery for astronomers. Besides some thermal anomalies and an off-center magnetic field, the planet is also unique in that it is the only one in the solar system that rotates on its side. With an axial tilt of 98 °, the planet experiences radical seasons and a day-night cycle at the poles, where a single day and a single night last 42 years.
Thanks to a new study by researchers at Durham University, the reason these secrets were finally discovered. With the help of NASA researchers and several scientific organizations, the team conducted simulations that showed Uranus could have had a massive impact in its past. This would not only explain the extreme inclination and magnetic field of the planet, but also explain why the outer atmosphere of the planet is so cold.
The study "The Impact of the Huge Impact on Early Uranus on Rotation, Internal Structures, Debris and Atmospheric Erosion", appeared recently in The Astrophysical Journal. The study was chaired by Jacob Kegerreis, a Ph.D. student at the Institute of Computational Cosmology, University of Durham, members of the Bay Area Environmental Research (BAER) Institute, NASA's Ames Research Center, Los Alamos National Laboratory, Descartes Labs , the University of Washington and UC Santa Cruz
For their study, funded by the Science and Technology Council, the Royal Society, NASA and Los Alamos National Laboratory, the team conducted the first high-resolution computer simulations of how massive collisions with Uranus would be Influence the evolution of the planet. As Kegerries recently stated in a Durham University press release:
"Uranus turns on its side with its axis nearly perpendicular to those of all the other planets in the solar system, which was almost certainly caused by a huge impact, but we know very little about how this actually happened and how otherwise such a violent event affected the planet. "
To determine how a huge impact on Uranus affected the team performed a suite of smoothed particle hydrodynamic (SPH) simulations Also used in the past to model the huge impact that led to the formation of the Moon (aka the Giant Impact Theory). All in all, the team performed more than 50 different crash scenarios with a powerful computer to see if it could restore Uranus' conditions.
In the end, the simulations confirmed that Uranus' tilt was caused by a collision with a massive object (between two and three masses of earth) that occurred about 4 billion years ago – that is, during the formation of the solar system. This was consistent with a previous study that suggested that a collision with a young rock and ice protoplanet might be responsible for the axial tilt of the uranium.
"Our findings confirm that the most likely result was that the young Uranus was engulfed in a cataclysmic collision with an object of the Earth's double mass, if not larger, it knocked on its side and set it to process the events that have contributed to the creation of today's planet, "said Kegerries.
In addition, the simulations answered a fundamental question about Uranus, which was asked in response to earlier studies. Essentially, scientists wondered how Uranus could retain its atmosphere after a fierce collision that theoretically inflated its hydrogen and helium gas layers. According to the simulations of the team, this was most likely due to the impact having caused a strike on the Uranus.
This would have changed Uranus' bias, but was not strong enough to eradicate its outer atmosphere. In addition, their simulations indicated that the impact of the rock and ice could have dropped into orbit around the planet. This would then be able to unite into the planet's inner satellites and change the rotation of existing moons in orbit around Uranus.
Last but not least, the simulations provided a possible explanation for how Uranus came from the middle of the magnetic field and its thermal anomalies. In short, the impact could create molten ice and crooked rocks within the planet (which explains its magnetic field). It could also have created a thin shell of debris near the edge of the ice sheet of the planet that would have trapped the inner heat, which might explain why the outer atmosphere of Uranus is extremely low in temperatures of -216 ° C (-357 ° F ) is exposed. 19659014] The concept of this artist shows the Uranus-sized exoplanet Kepler-421b, orbiting an orange star of type K about 1,000 light-years away from Earth. Credit: David A. Aguilar (CfA)
Beyond the help of astronomers to understand Uranus, one of the least-understood planets in the solar system, the study also has consequences when it comes to studying exoplanets. So far, most of the planets discovered in other star systems have been similar in size and mass to Uranus. Therefore, the researchers hope that their results will elucidate the chemical composition of this planet and explain how they have evolved.
Like Dr. Luis Teodoro from the BAER Institute and NASA Ames Research Center and one of the co-authors on "All Evidence suggests that planet Earth formation has huge implications, and this research will give us more insight into its impact on potentially habitable exoplanets."
In the coming years, additional missions are planned to study the outer solar system and the giant planets. Not only will these studies help astronomers understand how our solar system is evolving, they may also tell us what role gas giants play when it comes to habitability.
Further reading: Durham University, The Astrophysical Journal
Axial inclination, exoplanets, Featured, gas giant, Giant Impact Theory, ice giant, Uranus