It’s been 30 years since Voyager 2 did it’s last planetary flyby at Neptune. It took his picture less than five days before the spacecraft’s closest approach 25 August, 1989. The picture shows Neptune’s “Great Dark Spot”—a giant storm—and the bright clouds that follow the storm.
Image Credit: NASA
Hippocamp is a small moon of Neptune about 35 km in diameter. It orbits the planet in just under one Earth day. Its discovery in July, 2013, brought the number of Neptune’s known satellites to 14. Hippocampus is so dim that it was not notices when Voyager 2 flew by Neptune in 1989. It was detected by analyzing archived Neptune photographs taken by the Hubble Space Telescope.
This animation shows how Hippocamp might look close up.
Video Credit: ESA
Neptune has seasons which drive some of the features in its atmosphere, but those seasons are much longer than on Earth, lasting for decades rather than months.
This new Hubble view of Neptune shows a dark storm near the top center of the planet’s disc in the region currently experiencing “summer.” The feature is the fourth and latest 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 the Voyager flyby, Hubble has been out only telescope with sufficient sensitivity in blue light to track such elusive features which have appeared and faded quickly.
Image Credit: NASA / STScI