A nearly Earth-size storm system was spotted near Neptune’s equator, surprising scientists because no bright clouds have ever been seen in that location.
The storm is about 6,000 miles (9,000 kilometers) in length — about three-quarters Earth’s diameter — and is even huge compared to the size of Neptune: it spans nearly 30 degrees in both longitude and latitude. When astronomers studied the storm between June 26 and July 2, it appeared to get brighter.
“Seeing a storm this bright at such a low latitude is extremely surprising,” Ned Molter, a graduate student at the University of California, Berkeley, said in a statement. He saw the storm while doing a test run at the W. M. Keck Observatory at Mauna Kea, Hawaii. [Inside Gas Giant Neptune]
“Normally, this area is really quiet and we only see bright clouds in the mid-latitude bands, so to have such an enormous cloud sitting right at the equator is spectacular,” he added.
Because telescope time is competitive, opportunities to observe the gas giant planets are rare. This means that professional astronomers may have to wait months or years in between observations. Amateurs, however, can supplement some of the observations as telescope and imaging technology improves. (There was an amateur campaign to observe Neptune in 2015, with results recently published in the journal Icarus.)
Neptune storms have been captured by other professional observatories in the past. Voyager 2 saw a Great Dark Spot in 1989, which vanished by the time the Hubble Space Telescope examined the planet in 1994.
Hubble found a different storm at that time as well, which Molter and his adviser, Imke de Pater (also of UC Berkeley), thought they might have rediscovered in the Keck view…