UK observers with a clear sky an hour before sunrise on Friday 28 October should look very low in the east-southeast to see the slim crescent of the 27-day-old Moon just 1.8 degrees from largest planet Jupiter. In this simulated 10×50 binocular view, note that the Moon and Jupiter are joined by third-magnitude star gamma (γ) Virginis, commonly known as Porrima. This is a beautiful 2.5-arcsecond double star in medium-sized backyard telescopes when it is higher in the sky and seeing conditions are good. AN graphic by Ade Ashford.It’s time to celebrate the return of the king — the king of the planets, that is. Jupiter was in conjunction with the Sun on 26 September, but the solar system’s largest planet is now creeping back into the pre-dawn sky against the stellar backdrop of the constellation Virgo where it can be seen from the UK very low in the east-southeast about an hour before sunrise.
The configuration of Jupiter’s four Galilean moons Io, Europa, Ganymede and Callisto in the UK dawn twilight of Friday 28 October 2016 as seen with an erect-image telescope (north is up and east to the left). AN graphic by Ade Ashford.An added incentive to get up early to view Jupiter occurs on Friday 28 October when the slim crescent of a 27-day-old Moon lies just 1.8 degrees from the magnitude -1.7 planet as seen from the British Isles. The pair will look magnificent in binoculars where you might glimpse another object — third-magnitude star gamma (γ) Virginis, otherwise known as Porrima.
For telescope owners, Porrima holds another treat in store — though one that will be appreciated in the spring when the star lies higher in the sky and seeing conditions will be much improved. Gamma Virginis is a glorious double star with virtually identical components separated by just 2.5 arcseconds, hence a 4-inch (10-cm) aperture telescope employing a magnification of around 200x is required. Porrima is a true binary with a period of about 169 years and lies some 38 light-years from Earth.
Inside the magazine
For a comprehensive guide to observing all that is happening in the current month’s sky, tailored to Western Europe, North America and Australasia, obtain a copy of the October 2016 edition of Astronomy Now.
A decade-long question about the nature of dark spots on Europa’s surface has potentially been solved, with scientists suggesting that these spots are likely signs of irradiated sea salt from a subsurface ocean, deposited onto the surface through interactions with its rocky seafloor. If this is indeed the case, then these findings are an important consideration for assessing the habitability of the planet and whether it could support life or not.
When 252P/LINEAR passed just 14 lunar distances from Earth on 21 March, the comet was galloping across the far southern sky at a rate of almost ten degrees per day. Now rapidly heading north, 252P finally appears in the predawn UK sky. While moonlight will interfere with current observations, the comet is much brighter than predicted.
NASA’s Juno orbiter, making its 20th pass by Jupiter in May, provided another remarkable view of the giant planet’s turbulent atmosphere thanks to processing by a citizen scientist.
