A stunning new photo of Saturn reveals the planet's summer and winter in remarkable clarity

  • Astronomers just released a vivid new portrait of Saturn that captures summertime in the planet's northern hemisphere and blue-hued winter in the south.
  • The portrait is part of a project that studies how gaseous planets have evolved. 
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Astronomers released a vivid, beautiful photo of Saturn this week: It shows the planet's northern hemisphere in the height of summer, with a sun-induced reddish haze on top. A sliver of blue-hued winter is visible in the south, peeking out from beneath the planet's massive rings.

NASA's Hubble Space Telescope took the portrait on July 4, when Saturn was 839 million miles from Earth. It's part of a series of yearly pictures of Saturn and the solar system's other gas giants — Jupiter, Uranus, and Neptune — that began in 2018. The Outer Planets Atmospheres Legacy project, as it's known, studies weather patterns on the planets to help astronomers learn more about how these planets evolved.

In addition to revealing the stark differences between Saturn's winter and summer, the photo captured seasonal variations like atmospheric storms, which show up as tiny, knot-like disturbances.

The glimpse of winter towards Saturn's south pole is new — Hubble's last two portraits of the planet didn't capture that.  

According to Michael Wong, a planetary scientist at the University of California, Berkeley who works on the team that took the portrait, Saturn appears bluer in winter because sunlight interacts with elements in the planet's atmosphere to produce a haze, causing the planet to look yellowish-brown. Without direct sun and shaded by Saturn's rings, the haze disappears. Light scatters the same way it does on Earth, making it appear blue, like our sky. 

The reason Saturn looks more reddish in the summer, Wong added, may be that direct sunlight increases the amount of haze in the planet's atmosphere — hence the darker band around its north pole.

A year on Saturn is equivalent to 30 Earth-years, which should make each season last 7.5 Earth-years. But astronomers have observed Saturn's seasonal variations happening far faster than expected, Wong said.

"If we were just seeing seasonal changes, you'd expect to see 30 years for this type of cycle," he said. "We're seeing variations over just a year or two."

It's hard to know for sure why this is happening, Wong said, particularly because the annual portrait project is still new. Future images may reveal more about how and why the planet's seasons shift so quickly. 

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