NASA’s James Webb Space Telescope recently focused its attention on Uranus, an ice giant that spins on its side. Webb’s dynamic world was captured with rings, moons, storms, and other atmospheric features, including a seasonal polar cap. The image improves on a two-color version released earlier this year by including more wavelength coverage for a more detailed look.
Webb captured Uranus’ faint inner and outer rings, including the elusive Zeta ring – the extremely faint and diffuse ring closest to the planet. It also captured images of many of the planet’s 27 known moons, including some small moons hidden within the rings.
Uranus appeared as a calm, solid blue ball in visible wavelengths as seen by Voyager 2 in the 1980s. Webb is revealing a strange and dynamic ice world filled with exciting atmospheric features in infrared wavelengths.
Webb captured Uranus’ faint inner and outer rings, including the elusive Zeta ring – the extremely faint and diffuse ring closest to the planet. It also captured images of many of the planet’s 27 known moons, including some small moons hidden within the rings.
The planet’s seasonal north polar cloud cap is one of the most noticeable of these. Some details of the cap are more visible in these newer images than in the Webb image from earlier this year. The bright, white inner cap and the dark lane at the bottom of the polar cap, toward the lower latitudes, are examples.
Several bright storms can also be seen near and below the polar cap’s southern border. The number of these storms, and how frequently and where they appear in Uranus’s atmosphere, might be due to a combination of seasonal and meteorological effects.
The polar cap appears to become more prominent when the planet’s pole begins to point toward the Sun, as it approaches solstice and receives more sunlight. Uranus reaches its next solstice in 2028, and astronomers are eager to watch any possible changes in the structure of these features. Webb will help disentangle the seasonal and meteorological effects that influence Uranus’s storms, which is critical to help astronomers understand the planet’s complex atmosphere.
Because Uranus spins on its side at a tilt of about 98 degrees, it has the most extreme seasons in the solar system. For nearly a quarter of each Uranian year, the Sun shines over one pole, plunging the other half of the planet into a dark, 21-year-long winter.
Astronomers can now see Uranus and its unique features with unprecedented clarity thanks to Webb’s unparalleled infrared resolution and sensitivity. These details, particularly the close-in Zeta ring, will be invaluable in planning any future Uranus missions.
Uranus can also be used as a proxy for studying the nearly 2,000 similarly sized exoplanets discovered in recent decades. This “exoplanet in our backyard” can assist astronomers in understanding how planets of this size function, what their meteorology is like, and how they formed. This, in turn, can help us understand our own solar system as a whole by putting it in context.
