Astro Bob: New Webb images showcase Jupiter's intense auroras, dusky rings
The James Webb Space Telescope reveals a hidden face of the solar system's biggest planet.
Jupiter does everything in a big way. It's not only the largest planet but also one of brightest despite being fifth from the sun. Just catch it in the eastern sky after 10 o'clock and see for yourself. Several nights ago, I stayed up into the small hours, when Jupiter climbed high in the southern sky. More than once I mistook it — for just a split second — as a brilliant fireball.
NASA's James Webb Space Telescope recently turned its eye to the giant planet and returned several wonderfully detailed images. The telescope is optimized to "see" in infrared, light that lies just beyond the red end of the rainbow spectrum. Since the human eye can't see infrared, Webb photos have been mapped onto the visible spectrum. Using color filters, deeper infrared has been converted into red, while near-infrared (closer to visible red light) shows as blue.
In these images, scientists collaborated with citizen scientist Judy Schmidt of Modesto, California, to translate the Webb data into photos. Schmidt has a passion and talent for getting the most from spacecraft images. The final views here are composites of several images made through different colored filters.
A red filter highlights the Jovian aurora as well as light reflected from lower clouds and upper hazes on the planet. Yellow-green picks out hazes swirling around the North and South poles, while the cyan filter focuses on light coming from the deeper, main cloud bands.
Brightness in these photos indicates high altitude. The Great Red Spot, big enough to swallow Earth and then some, appears white because it's topped by high-altitude hazes. Likewise, the planet's equatorial regions. The many bright white spots and streaks are likely the cloud tops of smaller storms. To really appreciate the level of detail captured by the telescope, take a minute to explore this high-resolution image .
The wide-field picture (above) is even more remarkable because it captures so much at once. Webb see Jupiter's rings, which are a million times fainter than the planet, the tiny moons Amalthea and Adrastea, glowing auroras at both poles and even a few distant background galaxies.
“This one image sums up the science of our Jupiter system program, which studies the dynamics and chemistry of Jupiter itself, its rings, and its satellite system,” said Thierry Fouchet, a Paris Observatory professor involved in Webb observations.
Jupiter has 80 known moons , most of which are very small. Only four of them, named the Galilean moons , are bright enough to see in a small telescope. They're named for characters in ancient Greek myths: Io, Europa, Ganymede and Callisto.
Jupiter's auroras are both similar and different from those we see on Earth. Big solar storms can launch electrically charged particles across the solar system. When swept up by the Earth, they power the northern and southern lights. The same happens at Jupiter. But its primary source is its incredibly powerful magnetic field, which is 20,000 stronger than the Earth's.
Coupled with the planet's rapid spin (one day on Jupiter lasts just shy of 10 hours), strong electric currents are generated in the planet's polar regions. These attract electrically-charged sulfur and oxygen atoms spewed by volcanoes on the nearby moon Io and slam them into the atmosphere, producing auroras as well as bursts of of X-rays. Jupiter's a scary place!
Since hydrogen gas is abundant at the giant planet, much of the light at Jupiter comes from excited hydrogen. Here on Earth oxygen and nitrogen fill that role. Hydrogen glows brightly in both infrared and ultraviolet light.
While we can't see either "color" with our eyes, Jupiter's auroras also radiate plenty of visible light, too. NASA's Galileo spacecraft, which orbited the planet from 1995 to 2003, took the first photos of visible-light auroras on Jupiter's night side. Other types of excited atoms must be responsible for this glow. Perhaps Io's has a finger in that pie, too.
I hope the Webb makes regular visits to this big, stormy planet. Wouldn't you love to see more?