February 9, 2019

• HubbleSite: Image - Uranus and Neptune

  

  Hubble Reveals Dynamic Atmospheres of Uranus and Neptune

  During its routine yearly monitoring of the weather on our solar system's outer planets, NASA's Hubble Space Telescope has uncovered a new mysterious dark storm on Neptune (right) and provided a fresh look at a long-lived storm circling around the north polar region on Uranus (left).

  Like Earth, Uranus and Neptune have seasons, which likely drive some of the features in their atmospheres. But their seasons are much longer than on Earth, spanning decades rather than months.

  The new Hubble view of Neptune shows the dark storm, seen at top center. Appearing during the planet's southern summer, the feature is the fourth and latest mysterious dark vortex captured by Hubble since 1993.

  Hubble uncovered the latest storm in September 2018 in Neptune's northern hemisphere. The feature is roughly 6,800 miles across.

  To the right of the dark feature are bright white "companion clouds." Hubble has observed similar clouds accompanying previous vortices. The bright clouds form when the flow of ambient air is perturbed and diverted upward over the dark vortex, causing gases to freeze into methane ice crystals.

  It's unclear how these storms form.

  The snapshot of Uranus, like the image of Neptune, reveals a dominant feature: a vast bright cloud cap across the north pole.

  Scientists believe this feature is a result of Uranus' unique rotation. Unlike every other planet in the solar system, Uranus is tipped over almost onto its side. Because of this extreme tilt, during the planet's summer the Sun shines almost directly onto the north pole and never sets. Uranus is now approaching the middle of its summer season, and the polar-cap region is becoming more prominent

  Both planets are classified as ice giant planets. They have no solid surface but rather mantles of hydrogen and helium surrounding a water-rich interior, itself perhaps wrapped around a rocky core. Atmospheric methane absorbs red light but allows blue-green light to be scattered back into space, giving each planet a cyan hue.

  These images are part of a scrapbook of Hubble snapshots of Neptune and Uranus that track the weather patterns over time on these distant, cold planets.

  Analyzing the weather on these worlds also will help scientists better understand the diversity and similarities of the atmospheres of solar-system planets, including Earth.

  A Year On Uranus:

  Uranus has some of the strangest annual and seasonal variations of any planet in the Solar System. For one, the gas/ice giant takes about 84 Earth years (or 30,688.5 Earth days) to rotate once around the Sun.

  A Year On Neptune:

  Given its distance from the Sun, Neptune has the longest orbital period of any planet in the Solar System. As such, a year on Neptune is the longest of any planet, lasting the equivalent of 164.8 years

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