During its 40th close pass above Jupiter’s cloud tops, NASA’s Juno orbiter captured a spectacular image of Ganymede’s shadow from a distance of about 71,000 kilometres (44,000 miles), 15 times closer than the moon’s 1.1 million kilometre (666,000 mile) orbit. The elongated shadow marks a total eclipse of the Sun, a phenomenon that occurs much more frequently on Jupiter than on Earth thanks to its four Galilean moons. Such “shadow transits” across Jupiter are frequent targets for amateur astronomers, but the distance between the giant planet and Earth reduce those shadows to small black dots. From Juno’s perspective, the view is much more impressive. This enhanced colour image was processed from JunoCam data by citizen-scientist Thomas Thomopoulos.
Skywatchers in the UK and Western Europe should look low to the south-southeast an hour before sunrise on 31 January to see a beautiful naked-eye conjunction of Venus, the old crescent Moon and Jupiter, all within a span of 8½ degrees. But if you have a telescope and live in just the right place, you can also see the Moon hide a double star.
Skywatchers in Western Europe looking at the rising 13-day-old gibbous Moon in the south-southeast at dusk on Sunday, 27 May can also see prime-time Jupiter within the same binocular field of view. But look closer in the vicinity of the solar system’s largest planet and you’ll see an easily resolved double star – alpha Librae.