While the Hubble Space Telescope might be most famous for its images of beautiful and far-off objects like nebulae or distant galaxies, it also takes images of objects closer to home, including the planets right here in our own solar system. For the past 10 years, Hubble has been studying the outer planets in a project called OPAL (Outer Planet Atmospheres Legacy), capturing regular images of each of the four outer planets so scientists can study their changes over time.
The planets Jupiter, Saturn, Uranus, and Neptune are different in many ways from Earth, as they are gas giants and ice giants rather than rocky planets. But they do have some similar phenomena, such as weather that regularly changes, including epic events like storms that are so large they can be seen from space. Jupiter’s Great Red Spot, for example, the big orange-red eye shape that is visible on most images of the planet, is an enormous storm larger than the width of the entire Earth and which has been raging for centuries.
In Hubble’s images of Jupiter collected between 2015 and 2024, you can see how the spot moves and changes over time, with the bands of color created by bands of atmosphere moving and changing as well:
As for the other planets, data from OPAL has revealed information about Saturn’s “spokes,” which are dark patches in the planet’s rings that appear in a seasonal pattern and disappear again after just a few rotations. Uranus also has epic storms that are due to its unusual rotation, as the planet is tilted so far over that it rotates almost on its side. Part of one of its hemispheres can go without seeing any direct sunlight for periods of up to 42 years, which affects the way that polar ice caps form and melt.
And as for Neptune, the most distant planet in the solar system, it has its own strange dark spot. The peculiar thing about this spot is that it seems to be transitory, as sometimes it appeared in images and sometimes not. It turns out that it was not one single spot, but multiple spots that formed and faded over time, and which were also created by storms. Hubble was able to watch one of these storms appearing and fading, as well as track it moving toward the equator over time. It also showed that the cloudy weather there is influenced by the sun — even though Neptune receives just 0.1% of the intensity of sunlight we get here on Earth.
