Mysterious dark storm discovered on Neptune
- The storm appeared during the planet’s southern summer, the fourth and latest mysterious dark vortex captured by Hubble since 1993.
- Two other dark storms were discovered by the Voyager 2 spacecraft in 1989 as it flew by the remote planet.
- Since then, only Hubble has had the sensitivity in blue light to track these elusive features, which have appeared and faded quickly.
- A study led by Andrew Hsu, an undergraduate student at the University of California, Berkeley in the US, estimated that the dark spots appear every four to six years at different latitudes and disappear after about two years.
- Hubble uncovered the latest storm in September last year 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.
- Like Jupiter’s Great Red Spot, the dark vortices swirl in an anti-cyclonic direction and seem to dredge up material from deeper levels in the ice giant’s atmosphere.
- The Hubble observations show that as early as 2016, increased cloud activity in the region preceded the vortex’s appearance.
- The images indicate that the vortices probably develop deeper in Neptune’s atmosphere, becoming visible only when the top of the storm reaches higher altitudes.
- The snapshot of Uranus, like the image of Neptune, reveals a dominant feature: a vast bright stormy cloud cap across the north pole.
- Scientists believe this new 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.
- Neptune is the eighth and farthest known planet from the Sun in the Solar System.
- In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet.
- Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune.
- Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 AU (4.5 billion km).
- It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.