Saturn was first observed in the night sky in 1610 by Galileo, who was using such a rudimentary telescope that he couldn’t quite make out the fact that Saturn had rings at all. It wasn’t until 1659, when the Dutch astronomer Christiaan Huygens was gazing into the sky, that scientists realized the planet was decked out by massive rings.

Where those rings came from in the first place remains a mystery for scientists. One theory poses that they could have first formed after small icy moons in the planet’s orbit collided, breaking into millions of bits. In fact, the rings are comprised mostly of chunks of water ice that range between the size of tiny sand granules to boulders that are multiple feet in diameter.

Researchers are still working to figure out how the rings change with Saturn’s seasons. As the planet makes its slow trek around the sun—a journey that take 29.4 Earth years—it is exposed to the star by varying degrees, which may be altering the rings’ quantity of icy particles.

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