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Astronomers have observed Jupiter\u2019s legendary Great Red Spot (GRS), an anticyclone large enough to swallow Earth, for at least 150 years. But there are always new surprises \u2013 especially when the NASA\/ESA Hubble Space Telescope takes a close-up look at it.<\/p>\n
Hubble\u2019s new observations of the famous red storm, collected over 90 days between December 2023 to March 2024, reveal that the GRS is not as stable as it might look. The recent data show the GRS jiggling like a bowl of gelatin. The combined Hubble images allowed astronomers to assemble a time-lapse movie of the squiggly behaviour of the GRS.<\/p>\n
\u201cWhile we knew its motion varies slightly in its longitude, we didn\u2019t expect to see the size oscillate. As far as we know, it\u2019s not been identified before,\u201d\u00a0<\/i>said Amy Simon of NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland.\u00a0\u201cThis is really the first time we\u2019ve had the proper imaging cadence of the GRS. With Hubble\u2019s high resolution we can say that the GRS is definitively squeezing in and out at the same time as it moves faster and slower. That was very unexpected, and at present there are no hydrodynamic explanations.”<\/i><\/p>\n
Hubble monitors Jupiter and the other outer solar system planets every year through the Outer Planet Atmospheres Legacy program (OPAL) led by Simon, but these observations were from a program dedicated to the GRS. Understanding the mechanisms of the largest storms in the solar system puts the theory of hurricanes on Earth into a broader cosmic context, which might be applied to better understanding the meteorology on planets around other stars.<\/p>\n
Simon\u2019s team used Hubble to zoom in on the GRS for a detailed look at its size, shape, and any subtle colour changes.\u00a0\u201cWhen we look closely, we see a lot of things are changing from day to day,\u201d\u00a0<\/i>said Simon. This includes ultraviolet-light observations showing that the distinct core of the storm gets brightest when the GRS is at its largest size in its oscillation cycle. This indicates less haze absorption in the upper atmosphere.<\/p>\n
\u201cAs it accelerates and decelerates, the GRS is pushing against the windy jet streams to the north and south of it,\u201d\u00a0<\/i>said co-investigator Mike Wong of the University of California at Berkeley.\u00a0\u201cIt\u2019s similar to a sandwich where the slices of bread are forced to bulge out when there\u2019s too much filling in the middle.\u201d\u00a0<\/i>Wong contrasted this to Neptune, where dark spots can drift wildly in latitude without strong jet streams to hold them in place. Jupiter\u2019s Great Red Spot has been held at a southern latitude, trapped between the jet streams, for the extent of Earth-bound telescopic observations.<\/p>\n
The team has continued watching the GRS shrink since the OPAL program began 10 years ago. They predict it will keep shrinking before taking on a stable, less-elongated, shape.\u00a0\u201cRight now it\u2019s over-filling its latitude band relative to the wind field. Once it shrinks inside that band the winds will really be holding it in place,\u201d\u00a0<\/i>said Simon. The team predicts that the GRS will probably stabilise in size, but for now Hubble only observed it for one oscillation cycle.<\/p>\n
\u201cThis is a great example of the power of Hubble\u2019s exquisite imaging for monitoring of the atmospheres of the outer planets,\u201d\u00a0<\/i>said co-investigator Patrick Irwin of the University of Oxford. \u201cWith these new observations we were able to study the dynamics and evolution of the GRS over three months, building on our understanding of the long-term properties of Jupiter obtained from the OPAL program over the past decade.\u201d<\/i><\/p>\n
The researchers hope that in the future other high-resolution images from Hubble might identify other Jovian parameters that indicate the underlying cause of the oscillation.<\/p>\n
[Image description:<\/i>\u00a0Eight Hubble images showing Jupiter\u2019s Great Red Spot. The GRS appears as a bright red oval in the middle of cream-coloured cloud bands. The images trace changes in the GRS\u2019s size, shape, brightness, colour, and twisting, over a period of 90 days between December 2023 and March 2024.]<\/p>\n<\/p><\/div>\n<\/p><\/div>\n