How Webb just changed our concept of Uranus forever
Most pictures of Uranus in textbooks show it as a bright blue, featureless ball.
But the James Webb Space Telescope, the preeminent new observatory that senses light at invisible, infrared wavelengths, allows astronomers to see the seventh planet from the sun for what it truly is: a world crowned with rings, glorious rings.
NASA scientists say Uranus' rings have only been captured by two other cameras. They were first scoped out by the Voyager 2 spacecraft as it flew past in 1986. Later, the Keck Observatory in Hawaii spied the planet's ring system with advanced adaptive optics technology. The new space image follows on the heels of Webb's photo of Neptune last year, which also revealed ghostly rings around another ice giant within the solar system.
"JWST is a ring machine," said Stefanie Milam, a NASA planetary scientist, in a video shared by the Museum of Science in Boston. "This is one of the first times we've seen the Uranus rings in a very, very long time. They are really, really hard to see, and that's because they're made out of ice and dust."
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Uranus is also made from "icy" materials, such as water, methane, and ammonia, wrapped around a small rocky core. It is the only planet in the solar system tilted such that its equator is nearly at a right angle to its orbit, causing it to have extreme seasons. For Uranus, it takes 84 years to make a trip around the sun, which means it spends long stretches in constant sunlight and complete darkness.
Right now the planet, close to 2 billion miles from Earth, is experiencing late spring at its north pole, shown in the new image. Its northern summer will begin in five years. When Voyager 2 visited Uranus decades ago, it was summer at its south pole. The south pole now is out of view and facing the darkness of space.
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How many rings does Uranus have?
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Uranus has 13 known rings, 11 of which are visible in the new image. Some of these rings are so bright to Webb that when they are close together, they appear to merge into a larger ring. Nine are considered the main rings of the planet, and two are the fainter dusty rings discovered by Voyager 2. Scientists expect that future Webb images of the planet will reveal the other outer rings, according to a feature by the Space Telescope Science Institute in Baltimore.
"JWST is a ring machine."
Such vivid imagery taken within this solar system demonstrates the $10 billion space telescope's ability to collect extraordinary data not just of the distant universe — its main purpose — but of celestial objects closer to home. Scientists believe Webb will unleash a golden age in our understanding of the cosmos.
Webb found there’s a subtle, brightened spot at the pole in the sun, known as a polar cap. This polar cap is apparently unique to Uranus; It seems to appear when the pole enters direct sunlight in the summer and vanishes in the fall, according to NASA. The telescope's new observations will help researchers understand what's going on and how it works.
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Jessie Christiansen, a planetary scientist at NASA, was awed by the new picture of Uranus but shared side-by-side photos of Saturn and the ice giant on social media to compare the sizes of their ring systems.
Don't completely blow up your previous notions about ringed planets in this solar system, she cautioned in a tweet last week.
"Saturn is still the Queen of the Rings!" she said.