Free Astronomy Magazine January-February 2016

SPACE CHRONICLES the entire width of the vortex. This filamentary streamer ro- tates and twists throughout the ten-hour span of the Great Red Spot image sequence, distorted by winds that are blowing at 540 kilometres per hour. There is another feature of inte- rest in this new view of our giant neighbour. Just north of the planet’s equa- tor, researchers have found a rare wave struc- ture, of a type that has been spotted on the planet only once before, decades ago by the Voy- ager 2 mission, which was launched in 1977. In the Voyager 2 images the wave was barely visible and astronomers be- gan to think its appearance was a fluke, as nothing like it has been seen since, until now. The current wave was found in a re- gion dotted with cyclones and anti- cyclones. Similar waves — called baroclinic waves — sometimes ap- pear in the Earth’s atmosphere where cyclones are forming. The wave may originate in a clear layer beneath the clouds, only be- coming visible when it propagates up into the cloud deck, according to the researchers. The observations of Jupiter form part of the Outer Planet Atmo- spheres Legacy (OPAL) program- me, which will allow Hubble to ded- icate time each year to observing the outer planets. In addition to Jupiter, Neptune and Uranus have already been observed as part of the programme and maps of these planets will be placed in the public archive. Saturn will be added to the series later. The collection of maps that will be built up over time will help scien- tists not only to understand the atmospheres of giant planets in the Solar System, but also the at- mospheres of our own planet and of the planets that are being dis- covered around other stars. U sing the NASA/ESA Hubble Space Telescope scien- tists have produced new maps of Jupiter. The data in the Jupiter map shown here were taken during the Hubble Outer Planet Atmospheres Legacy (OPAL) pro- gramme. This map has been projected onto a rotating globe, which allows us to see the whole of the plane- tary surface. [NASA, ESA, A. Simon (GSFC), M. Wong (UC Berkeley), G. Orton (JPL-Caltech), and G. Bacon (STScI)] I n overlaying both created maps on a globe, the move- ment of the dust lanes becomes visible. This allows scientists to calculate the wind speed in Jupiter’s atmo- sphere. [NASA, ESA, A. Simon (GSFC), M. Wong (UC Berkeley), G. Orton (JPL-Caltech), and G. Bacon (STScI)] decreasing in size at a noticeably faster rate from year to year for some time. But now, the rate of shrinkage seems to be slowing again, even though the spot is still about 240 kilometres smaller than it was in 2014. The spot’s size is not the only change that has been captured by Hubble. At the centre of the spot, which is less intense in colour than it once was, an unusual wispy fila- ment can be seen spanning almost n