The planets in our solar system aren’t static. Like Earth, the other planets also experience seasonal variations with atmospheric changes occurring throughout the year. That’s why each year the Hubble Space Telescope snaps images of the outer planets of our solar system — Jupiter, Saturn, Uranus, and Neptune — so astronomers can see how they are changing over time.
The NASA/ESA Hubble Space Telescope has completed its annual grand tour of the outer Solar System for 2021. Note: The planets are not shown to scale in this image.
The images of this year’s “Grand Tour” of the outer solar system have just been released and they show the gas giants and ice giants which are so different from the inner, rocky planets of Mercury, Venus, Earth, and Mars. These outer planets are much larger, and because they are so much further from the sun — the farthest, Neptune, orbits at a distance 30 times the distance between Earth and the sun — they are also extremely cold. They are composed of different materials too, being made up of what the European Space Agency describes as, “chilly gaseous soups of hydrogen, helium, ammonia, methane, and other trace gases around a packed, intensely hot, compact core.”
This year’s images show the ever-changing atmosphere of Jupiter, in which new storms regularly appear and form shapes called barges. Another feature shown in the image is the “Red Spot Jr.,” a smaller spot that has appeared beneath Jupiter’s famous Great Red Spot.
“Every time we get new data down, the image quality and detail in the cloud features always blow me away,” said Amy Simon of the Goddard Space Flight Center in Greenbelt, Maryland. “It strikes me when I look at Jupiter, in the barges or in the red band right below, you can see cloud structures that are clearly much deeper. We’re seeing a lot of structure here and vertical depth variation.”
Saturn is approaching autumn in its northern hemisphere, where there are color changes in its bands, and in the southern hemisphere, you can see the remnants of winter in the blue color around the planet’s southern pole.
“This is something we can best do with Hubble. With Hubble’s high resolution, we can narrow things down to which band is actually changing,” said Michael Wong of the University of California, Berkeley. “If you were to look at this through a ground-based telescope, there’s some blurring with our atmosphere, and you’ll lose some of those color variations. Nothing from the ground will get visible-light images as sharp as Hubble’s.”
Finally, Uranus and Neptune show changes too, with the bright northern pole of Neptune caused by ultraviolet radiation and a darkened northern hemisphere of Uranus and a dark spot that moves around the planet.