New images from the NASA/ESA/CSA James Webb Space Telescope show the ice giant Uranus, its faint rings and several moons.
This image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam) on February 6, 2023, reveals stunning views of the planet’s rings. The planet displays a blue hue in this representative-color image, made by combining data from two filters (F140M, F300M) at 1.4 and 3 microns, which are shown here as blue and orange, respectively. Image credit: NASA / ESA / CSA / STScI / J. DePasquale, STScI.
Uranus is the seventh planet from the Sun at a distance of about 2.9 billion km (1.8 billion miles).
It was the first planet found with the aid of a telescope, Uranus was discovered in 1781 by the German-born British astronomer William Herschel, although he originally thought it was either a comet or a star.
Uranus has the third-largest diameter in our Solar System, and is surrounded by 13 faint rings and 27 moons.
One day on Uranus takes about 17 hours. And the planet makes a complete orbit around the Sun in about 84 Earth years.
Uranus is characterized as an ice giant due to the chemical make-up of its interior. Most of its mass is thought to be a hot, dense fluid of ‘icy’ materials — water, methane, and ammonia — above a small rocky core.
Winds blow in its deep blue-green atmosphere mainly east to west at speeds up to 900 km per hour (560 mph), in spite of the small amounts of energy available to drive them.
The atmosphere is almost equal to Neptune’s as the coldest in the Solar System with cloud-top temperatures in the minus 218-degree Celsius (minus 360 degree Fahrenheit) range.
Uranus is the only solar system planet whose equator is nearly at a right angle to its orbit, with a tilt of 97.77 degrees — possibly the result of a collision with an Earth-sized object long ago.
This unique tilt causes the most extreme seasons in the Solar System. For nearly a quarter of each Uranian year, the Sun shines directly over each pole, plunging the other half of the planet into a 21-year-long, dark winter.
“Currently, it is late spring for the northern pole, which is visible here; Uranus’ northern summer will be in 2028,” Webb astronomers explained.
“In contrast, when NASA’s Voyager 2 spacecraft visited Uranus it was summer at the south pole.”
“The south pole is now on the ‘dark side’ of the planet, out of view and facing the darkness of space.”
This Webb image shows Uranus and six of its 27 known moons (most of which are too small and faint to be seen in this short exposure). Image credit: NASA / ESA / CSA / STScI / J. DePasquale, STScI.
The new infrared image from Webb’s Near-Infrared Camera (NIRCam) combines data from two filters at 1.4 and 3 microns, which are shown here in blue and orange, respectively. The planet displays a blue hue in the resulting representative-color image.
“When Voyager 2 looked at Uranus, its camera showed an almost featureless blue-green ball in visible wavelengths,” the astronomers said.
“With the infrared wavelengths and extra sensitivity of Webb, we see more detail, showing how dynamic the atmosphere of Uranus really is.”
“On the right side of the planet there’s an area of brightening at the pole facing the Sun, known as a polar cap.”
“This polar cap is unique to Uranus — it seems to appear when the pole enters direct sunlight in the summer and vanish in the fall.”
“These Webb data will help scientists understand the currently mysterious mechanism.”
“Webb revealed a surprising aspect of the polar cap: a subtle enhanced brightening at the center of the cap.”
“The sensitivity and longer wavelengths of Webb’s NIRCam may be why we can see this enhanced Uranus polar feature when it has not been seen as clearly with other powerful telescopes like the NASA/ESA Hubble Space Telescope and Keck Observatory.”
“At the edge of the polar cap lies a bright cloud as well as a few fainter extended features just beyond the cap’s edge, and a second very bright cloud is seen at the planet’s left limb,” they said.
“Such clouds are typical for Uranus in infrared wavelengths, and likely are connected to storm activity.”
“Uranus has 13 known rings and 11 of them are visible in this Webb image,” the researchers said.
“Some of these rings are so bright with Webb that when they are close together, they appear to merge into a larger ring.”
“Nine are classed as the main rings of the planet, and two are the fainter dusty rings (such as the diffuse zeta ring closest to the planet) that weren’t discovered until the 1986 flyby by Voyager 2.”
“We expect that future Webb images of Uranus will reveal the two faint outer rings that were discovered with Hubble during the 2007 ring-plane crossing.”
