The Hubble Space Telescope has taken new photos of the Great Red Spot on Jupiter, showing the massive storm is smaller than ever before.
For decades, the feature has become less noticeable. Beginning in 2012, observers around the world noticed an increase in the rate at which the storm was shrinking. However, this new Hubble image shows exactly how dramatic the changes have become.
"Historic observations as far back as the late 1800s gauged the storm to be as large as 25,500 miles on its long axis. NASA Voyager 1 and Voyager 2 flybys of Jupiter in 1979 measured it to be 14,500 miles across. In 1995, a Hubble photo showed the long axis of the spot at an estimated 13,020 miles across. And in a 2009 photo, it was measured at 11,130 miles across," NASA researchers wrote in a press release about the finding.
Today, the storm is shrinking at a rate of 580 miles per year, now measuring just 10,250 miles in length. In the last few years, the storm has also started to change shape, from an oval to a circle.
The Great Red Spot is a high-pressure storm system. In many ways, this feature is much like the most severe storms on Earth, but much larger. Astronomers are not certain why the massive feature is fading.
Small eddies, or whirlpools, are joining the main storm. Astronomers believe these events may be draining energy from the main system.
"We hypothesized these may be responsible for the accelerated change by altering the internal dynamics and energy of the Great Red Spot," Amy Simon of NASA's Goddard Space Flight Center, said.
Shrinking of the spot was first measured in the 1930's, and astronomers have recorded declining measurements from that time. The effect has been observed by amateur astronomers who have viewed Jupiter for decades.
"Recent Hubble Space Telescope observations confirm that the spot is now... the smallest diameter we've ever measured," Simon said.
No one knows how long the Great Red Spot has raged, but Gian Domenico Cassini made the first mentions of a permanent storm on the planet in 1665, and the storm has been under continuous monitoring since 1878.
The Great Red Spot turns counter-clockwise, rotating once every six Earth-days. The feature is cooler than surrounding areas of Jupiter's atmosphere. Astronomers also believe the storms lies in the upper regions of the giant planets gaseous cover.
The latest Hubble image of the decaying Great Red Spot of Jupiter was taken on 21 April 2014.