The new Great Dark Spot was previously spotted in September 2018 but was postponed due to a technical fault.
For the first time since Voyager 2 spotted the ‘Great Dark Spot’ in 1989, Hubble telescope has identified a gigantic, dark storm on Neptune. Neptune, like earth, has seasons but with a larger span of decades. This storm is developed in the southern summer of the planet that is 11000 km long and 5000 km wide. It was first spotted by Hubble in September 2018, but due to a technical fault, further observations were postponed. However, a fix was made in November only to resume observations. The team at work observed that over a period of 20 hours, the new Great Dark Spot has moved across the Neptunian Sky at a speed of 972 km/h.
The researchers at work looked back at some previous images, taken from 2015 to 2017. Hubble has been capturing pictures of Neptune since 2015, as a part of the Outer Planet Atmospheres Legacy (OPAL) project. During the analysis, the team observed that no such dark spots were spotted between 2015 and 2017, but several white clouds were noticed. These images indicate that vortices probably develop deeper into Neptune’s atmosphere. They only become visible when the top of the storm reaches higher altitudes.
The researchers say a new storm appears on Neptune every four to six years whereas two years is the usual lifespan. They also tried to find that how many dark posts Hubble can spot. The team did simulations of 8000 dark spots and matched them with 256 archival images. According to the researchers, Hubble can spot 70 percent of storms that last up to one year and 95 percent of storms that last two years. The team is currently observing the further movement of the storm and study how the planet’s changing wind affects them.