Scientists have discovered a giant new storm on Neptune that’s about the size of our planet.

The discovery was made by Ned Molter from the University of California, Berkeley. Using the Keck Observatory in Hawaii, he was able to spot this massive storm.

It measures about 9,000 kilometers (5,600 miles) across, which is one-third the length of Neptune’s radius. It was seen around Neptune’s equator, a region of the planet not normally associated with storms like this.

"Seeing a storm this bright at such a low latitude is extremely surprising," said Molter in a statement. "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."

Storms are normally seen on Neptune closer to the poles, around 15 to 60 degrees north or south of the equator. This is thought to be the first storm ever seen in this location.

Wind speeds at Neptune’s equator can reach up to 1,600 kilometers per hour (1,000 mph), which is more than 10 times stronger than anything on Earth.

It’s thought this particular storm may be driven by a dark vortex inside Neptune. The clouds of the storm span many latitudes, so something must be holding it together. It may also be a huge convective cloud, although if so this should dissipate in about a week.

Neptune’s most famous storm is arguably its Great Dark Spot, imaged by the Voyager 2 spacecraft in 1989, which spanned up to 13,000 kilometers (8,000 miles) across. Unlike storms on Jupiter, which can last for hundreds of years, those on Neptune typically only last a few years or so. This latest storm hints at some sort of regular event on the planet.

"This shows that there are extremely drastic changes in the dynamics of Neptune's atmosphere, and perhaps this is a seasonal weather event that may happen every few decades or so," said Imke de Pater, Molter’s advisor, in the statement.

Learning more about Neptune’s atmosphere can help us understand more about its global circulation. With many exoplanets found to be the size of Neptune, this can tell us more about the atmospheres of worlds outside our Solar System.