Astronomers have unveiled new high-resolution infrared images of Uranus, revealing in detail the bizarre weather of the seventh planet from the Sun.
A paired infrared picture of Uranus reveals a raft of new details about the planet’s enigmatic atmosphere. The north pole of Uranus, to the right in the picture, is characterized by a swarm of storm-like convective features, and an unusual scalloped pattern of clouds encircles the planet’s equator (Lawrence Sromovsky / Pat Fry / Heidi Hammel / Imke de Pater / University of Wisconsin-Madison)
The Uranus’ deep blue-green atmosphere is thick with hydrogen, helium and methane. Winds blow mainly east to west at speeds up to 560 miles (900 km) per hour, in spite of the small amounts of energy available to drive them. Its atmosphere is almost equal to Neptune’s as the coldest in our Solar system with cloud-top temperatures in the minus 360-degree F (minus 218 C) range.
“Large weather systems, which are probably much less violent than the storms we know on Earth, behave in bizarre ways on Uranus,” said Dr Larry Sromovsky, a planetary scientist with the University of Wisconsin-Madison and lead author of a new study.
“Some of these weather systems,” Dr Sromovsky said, “stay at fixed latitudes and undergo large variations in activity. Others are seen to drift toward the planet’s equator while undergoing great changes in size and shape. Better measures of the wind fields that surround these massive weather systems are the key to unraveling their mysteries.”
The astronomers used a new infrared technique at the Keck Observatory to detect smaller weather features whose movements can help trace the planet’s pattern of blustery winds. “We’re seeing some new things that before were buried in the noise,” Dr Sromovsky said.
“These images reveal an astonishing amount of complexity in Uranus’s atmosphere. We knew the planet was active, but until now much of the activity was masked by noise in our data,” explained Dr Heidi Hammel of the Association of Universities for Research in Astronomy.
“The complexity of Uranus’s weather is puzzling,” Dr Sromovsky added. “The primary driving mechanism must be solar energy because there is no detectable internal energy source. But the Sun is 900 times weaker there than on Earth because it is 30 times further from the Sun, so you don’t have the same intensity of solar energy driving the system. Thus the atmosphere of Uranus must operate as a very efficient machine with very little dissipation. Yet the weather variations we see seem to defy that requirement.”
“The new images of the planet are the most richly detailed views of Uranus yet obtained by any instrument on any observatory. No other telescope could come close to producing this result,” Dr Sromovsky concluded.
