Observers in eastern Australia, all of New Zealand, and parts of the South Pacific will see the planet Uranus pass behind the waning crescent Moon in the early morning of June 12, 2015. The precise timing of the event depends on your location. In Adelaide, Australia, Uranus passes behind the Moon at 18:49 UT, just after moonrise, and emerges from the dark part of the crescent Moon’s face at 19:57 UT. In Sydney the occultation begins at 19:01 UT and ends at 20:17 UT.
Observers in the rest of the world will see Uranus close to the crescent Moon in the eastern pre-dawn sky. This presents an excellent opportunity to spot this distant ice giant with a pair of binoculars or a small telescope. Slooh will be presenting live views of the event courtesy of our Australian feed partners. Join us to watch live views of the Solar System in motion!
Similar to the giant gas planets Jupiter and Saturn, their smaller cousins, Uranus and Neptune, have long been known to harbor swirling clouds and violent winds churning up their atmospheres. Massive bands of jet streams encircling the entire planet have been observed in both cases. But given that Uranus’ atmosphere is believed to be thick enough to swallow the entire Earth, it was not known just how far the weather perturbations reach into the planet’s interior.
Now a team of planetary scientists with the University of Arizona’s Lunar and Planetary Laboratory, including William Hubbard and Adam Showman, has published the results of new analyses that put an upper limit to the weather zone on Uranus and Neptune. According to their data, reported in the journal Nature, the atmosphere on both planets goes from screaming winds of infernal violence to dead-quiet at a much shallower depth than previously thought.
“Our analyses show that the dynamics are confined to a thin weather layer no more than about 680 miles deep,” said Hubbard. “This number is an upper limit, so in reality, it is possible that the atmosphere quiets down even shallower than that.”
Uranus’s highly tilted axis makes it something of an oddball in our Solar System. The accepted wisdom is that Uranus was knocked on its side by a single large impact, but new research to be presented on Thursday 6th October at the EPSC-DPS Joint Meeting in Nantes rewrites our theories of how Uranus became so tilted and also solves fresh mysteries about the position and orbits of its moons. By using simulations of planetary formation and collisions, it appears that early in its life Uranus experienced a succession of small punches instead of a single knock-out blow. This research has important ramifications on our theories of giant planet formation.
Uranus is unusual in that its spin axis is inclined by 98 degrees compared to its orbital plane around the Sun. This is far more pronounced than other planets, such as Jupiter (3 degrees), Earth (23 degrees), or Saturn and Neptune (29 degrees). Uranus is, in effect, spinning on its side.
The generally accepted theory is that in the past a body a few times more massive than the Earth collided with Uranus, knocking the planet on its side. There is, however, one significant flaw in this notion: the moons of Uranus should have been left orbiting in their original angles, but they too lie at almost exactly 98 degrees.
This long-standing mystery has been solved by an international team of scientists led by Alessandro Morbidelli (Observatoire de la Cote d’Azur in Nice, France), who will be presenting his group’s research on Thursday 6th October at the EPSC-DPS Joint Meeting in Nantes, France.