The Night Sky This Month

Northern HemisphereIan Morison tells us what we can see in the Northern Hemisphere night sky during December 2017.The PlanetsJupiter - Jupiter is now a pre-dawn object rising some 2 hours before the Sun at the beginning of the month with its 31 arc second disk, shining at a magnitude of -1.7, to be seen under clear skies. As the month progresses, its apparent diameter increases to 33 arc seconds and it brightens to magnitude -1.8. The low elevation will hinder our view, but the equatorial bands and up to four of its Gallilean moons should be visible. Saturn - Saturn will not be visible this month as it leaves the evening sky on its way to superior conjunction (passing behind the Sun) on December 21st before it reappears in the pre-dawn sky next year. Mercury - Mercury, just visible in the evening sky at the end of November, will not be seen for three weeks as it passes between the Earth and the Sun on December 13th (inferior conjunction). From the 20th or so it brightens rapidly in the pre-dawn sky to rea