Now hotshot Mike grabs Uranus

Here is another fantastic image just taken by planetary astronomer Mike Brown at his observing eyrie on Hawaii, but this time of Uranus including storm clouds, its rings and some moons.

Uranus and Miranda pictured today (Credit: Mike Brown/CalTech)

Mike wowed us all yesterday with his infrared views of distant planet Neptune and its largest moon Triton. Today he has used one of the 10-meter (33ft) twin telescopes at the W. M. Keck Observatory to home in on its inner neighbour Uranus, another ice giant.

The infrared image was basically taken to help Mike, a professor at the California Institute of Technology, to get his bearings before studying prime target Miranda the satellite that is glowing brightest at top left. But it also clearly shows what are really very dark rings – a remarkable feat since they were only discovered in 1977. You may also spot two other moons of Uranus, Puck and Desdemona.

Mike broke off from observing to tell Skymania News: “Miranda, the moon up and left is our main target at the moment. Bright spots on Uranus’s disk are high clouds. There are two obvious hot pixels (imaging artifacts) immediately to the right and just below the planet. Everything else I think is real with Miranda up and left, Puck up and right, and Desdemona really faint to the right.

“All of the bright stuff on the disk is storm clouds. Same story as Neptune, the atmosphere absorbs most of the light at these wavelengths (1.8 microns) so unless something is reflecting up high, like a cloud, Uranus is really dark. Because it is so dark, we can relatively easily see the rings, which themselves quite faint.”

Uranus, the seventh planet from the Sun, is easy to spot with binoculars and may be glimpsed with the unaided eye on a clear dark night if you get away from streetlights. A telescope will show it as a tiny blue-green disk in visible light. The planet’s atmosphere is made up mainly of hydrogen, helium plus methane which provides the bluish colour.

Some of the fastest winds in the solar system have been detected on Uranus, blowing at more than 500 mph (800 km). Storms, which show as bright spots in infrared light.

When Uranus’s moons were first spotted, they were seen to be circling it at a remarkably steep angle. This was a clue to one of the planet’s amazing characteristics – its axis is tilted by nearly 98 degrees to the plane of the ecliptic meaning that it is effectively spinning on its side. A cosmic collision with another world is thought to be to blame.

Miranda imaged by Voyager 2 in 1986 (NASA)

The dusky rings were discovered by chance when scientists aboard a flying telescope, NASA’s Kuiper Airborne Observatory, were airborne to watch the planet occult, or pass in front of, a star. The mission was to study Uranus’s atmosphere but the team were surprised to see the star blink out of view five times before and five times afer it disappeared behind the planet.

Solar System explorer Voyager 2 looked at the rings – it is now known that there are 13 of them – as it flew by and they have also been photographed by the Hubble space telescope. They are believed to be the remains of a shattered moon.

Interestingly, the man who discovered Uranus in 1781, William Herschel, thought he saw a reddish ring around Uranus in 1789. But because nobody else supported his observation, it is assumed that he imagined them.

Uranus’s moons are all named after characters from the works of Shakespeare or another English poet, Alexander Pope. Miranda, the fifth to be found, was detected by US astronomer Gerard Kuiper in 1948. It has a diameter of 290 miles (470 km), and a chaotic, cratered landscape created by tidal forces, including vast canyons, fractures and features caused by eruptions of icy lava. Three strange oval features resemble race tracks.

UK planetary scientist Chris Arridge is working to develop a potential joint mission to Uranus by NASA and the European Space Agency.


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