Weymouth Astronomy

The Planets - December 2017

Observing the planets can be extremely rewarding. Everyone remembers the first time they observed Saturn and it's rings or the gas giant Jupiter and it's Galillean Moons. Solar System


Mercury the innermost planet, just visible in the evening sky at the end of November will not be seen for the first three weeks of December 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 reach a magnitude of -0.3 by months end when some 23 degrees away from the Sun.


Venus was seen in a close conjunction with Jupiter on the 13th November. Moving back towards the Sun it rises just 45 minutes before the Sun at the start of December and is lost in the Sun's glare around the 12th of the month on its way towards superior conjunction (on the far side of the Sun) on January 9th.


At the start of the month Mars lies in Virgo just 3 degrees up to the left of Spica, Alpha Virginis. Now a morning object at the start of its new apparition, it rises four hours or so earlier than the Sun. Mars crosses from Virgo into Libra on the 21st, moving eastwards to closely approach Jupiter on New Years Eve before a very close conjunction with it on the 7th of January.


Jupiter is now a pre-dawn object rising some 2 hours before the Sun at the beginning of the month shining at a magnitude of -1.7 to be seen under clear skies. The low elevation will hinder our view, but the equatorial bands and up to four of its Gallilean moons should be visible.


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.

Information collated from Jodrell Bank and Astronomy Now magazine