"Jupiter's north polar region is coming into view as NASA's Juno spacecraft approaches the giant planet. This view of Jupiter was taken on August 27, when Juno was 437,000 miles (703,000 kilometers) away." Image Source: NASA/JPL-Caltech/SwRI/MSSS.
NASA's Juno probe, launched from Florida on 5 August 2011, entered Jupiter's orbit on 4 July 2016; it will remain in orbit for 20 months, testing Jupiter's atmosphere and magnetosphere until February 2018. The American space agency continues the Decadal Solar System Exploration Survey; Jupiter has previously been visited by Pioneer 10 (1973) and Pioneer 11 (1974); Voyager 1 (1979) and Voyager 2 (1979); the Galileo spacecraft (1995-2003); Ulysses (1992 and 2004); the Cassini-Huygens mission (2000); and the New Horizons probe (2007). This Juno mission brings full circle four centuries of research on the great planet, which has three outer Gossamer rings and 67 moons. There are two Jovian lunar exploration missions proposed by the Europeans and Russians and NASA for the 2020s. More photos will follow from the Juno mission:
"NASA's Juno mission successfully executed its first of 36 orbital flybys of Jupiter today [27 August 2016]. The time of closest approach with the gas-giant world was 6:44 a.m. PDT (9:44 a.m. EDT, 13:44 UTC) when Juno passed about 2,600 miles (4,200 kilometers) above Jupiter's swirling clouds. At the time, Juno was traveling at 130,000 mph (208,000 kilometers per hour) with respect to the planet. This flyby was the closest Juno will get to Jupiter during its prime mission. 'Early post-flyby telemetry indicates that everything worked as planned and Juno is firing on all cylinders,' said Rick Nybakken, Juno project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.There are 35 more close flybys of Jupiter planned during Juno's mission (scheduled to end in February 2018). The August 27 flyby was the first time Juno had its entire suite of science instruments activated and looking at the giant planet as the spacecraft zoomed past.'We are getting some intriguing early data returns as we speak,' said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. 'It will take days for all the science data collected during the flyby to be downlinked and even more to begin to comprehend what Juno and Jupiter are trying to tell us.'"
In 1610-1611, Galileo discovered Jupiter's four largest moons; the discovery that a planet could have smaller planets revolving around it contradicted and revolutionized Aristotelian astronomy. Galileo showed the Doge of Venice how to use the telescope (1857 fresco by Giuseppe Bertini (1825-1898)). Image Source: Wiki.
On the bottom of this page, in 1610, Galileo first noted an observation of the four largest moons of Jupiter. The top of the page was an earlier draft of a letter to the Doge of Venice, recommending the telescope as an instrument of warfare. Galileo published a full description in Sidereus Nuncius (The Sidereal Messenger) in March 1610 (read it online here in Latin and in English here). Image Source: Wiki.
Caption for the above photograph: "This is an image of a draft letter written by Galileo Galilei in August 1609 to Leonardo Donato, Doge of Venice, and currently held in the University of Michigan Harlan Hatcher Graduate Library's Special Collections. The University of Michigan says the following about its history: 'In 1609 [Galileo] received a description of a telescope which had been developed the year before in the Dutch town of Middelburg by an optician, one Jan Lippershey. Applying his knowledge of optical science, Galileo built such a glass or telescope for himself, and in the draft letter shown above offers his new 'occhiale' to the Doge of Venice for use in warfare. The final letter, revised from this draft, was sent on August 24, 1609. It is in the State Archives in Venice. The lower part of this sheet shows the use to which Galileo put this optical device: as he viewed the skies on successive evenings in January, 1610, he noted his first observations of the planet Jupiter and four of Jupiter's moons.' This item is cataloged in the collections as: Galileo Galilei (1564-1642). Draft of a letter to Leonardo Donato, Doge of Venice. Circa August, 1609. Gift of Tracy W. McGregor, 1938. According to Scientific American, when it was donated it was known to be a draft of the letter in the Venice State Archives, but the significance and meaning of the material on the lower half was unrecognized. Only in the late 1970s was it determined that these 'doodles' in fact depict the positions of the Galilean moons on the nights in early January when Galileo first observed them, thus proving that this document contains the original notes he took on the nights he made his observations. ... The University of Michigan translates the upper half thus: 'Most Serene Prince. Galileo Galilei most humbly prostrates himself before Your Highness, watching carefully, and with all spirit of willingness, not only to satisfy what concerns the reading of mathematics in the study of Padua, but to write of having decided to present to Your Highness a telescope that will be a great help in maritime and land enterprises. I assure you I shall keep this new invention a great secret and show it only to Your Highness. The telescope was made for the most accurate study of distances. This telescope has the advantage of discovering the ships of the enemy two hours before they can be seen with the natural vision and to distinguish the number and quality of the ships and to judge their strength and be ready to chase them, to fight them, or to flee from them; or, in the open country to see all details and to distinguish every movement and preparation.'"
NASA's Juno approach movie of Jupiter and the Galilean moons, Io, Europa, Ganymede, and Callisto, showing the view from June 2016. These moons are among the largest in the solar system and are roughly half to a quarter the size of Earth. Video Source: NASA/Youtube.
Juno captures the magnetic roar of Jupiter (24 June 2016). Video Source: NASA/Youtube.
Video Source: Youtube/NASA.
Callisto, photo taken by the Galileo spacecraft (May 2001). Image Source: NASA/JPL/DLR(German Aerospace Center) via Wiki.
Europa, photo taken by the Galileo spacecraft (September 1996). Image Source: NASA/JPL/DLR via Wiki.
Io, photo taken by the Galileo spacecraft (July 1999). Image Source: NASA/JPL/University of Arizona via Wiki.