Sky Notes for October 2012, with James Abbott #stargazing
October brings the most marked change to the skies as the Autumn nights set in. With the Sun moving southwards in the sky and the clocks going back, the Sun sets as early as 4.30pm GMT by the end of the month compared to 6.30pm BST at the start of the month.
BST ends on Sunday 28th October with the clocks going back one hour.
Full Moon is on the evening of 29th October but on the 1st the Moon will only be just past Full – so almost another month with 2 full Moons.
Jupiter continues to brighten throughout October and to become better placed in the evening sky. Looking East on the late evening of the 5th, the waning Moon will pass less than 2 degrees below Jupiter, with both objects fitting in the field of view of binoculars. By the end of the month, Jupiter is over 30 degrees in altitude by 10pm GMT and with an equatorial diameter of 47 arc seconds will reveal a lot of detail in telescopes under good seeing conditions.
In the pre-dawn Eastern skies Venus remains prominent throughout October and will be very close to the bright star Regulus on the morning of the 3rd. The thin crescent waning Moon will be fairly close to Venus on the morning of the 12th.
In the second half of the month the Orionid meteors are active, peaking between the 20th and the 22nd. The Orionids are the dusty debris left in the orbit of Halley’s Comet. They enter the top of our atmosphere at a high velocity approaching 70 kilometers per second. The bright streaks caused by the dust burning up can be coloured, with observers sometimes reporting yellow or green meteors. Orion does not rise above the Eastern horizon until late evening at this time of year so the best chance of seeing many meteors is to wait until around midnight and afterwards to look, also by which time the Moon has set.
If it is clear for the Orionids, the meteors will be seen against the backdrop of the highest concentration of bright stars in the Northern sky, with the main winter constellations of Orion and Gemini following Taurus and Auriga, and with Jupiter adding further to the spectacle.
Looking ahead to 2013, 2 comets could become bright objects.
In March, 2011 L4 (PanSTARRS) will emerge from evening twilight in the West as bright as first magnitude. Potentially an even brighter comet though will be 2012 S1 (ISON) in November and December 2013. This recently discovered comet is believed to be on its first passage towards the inner solar system. It will pass extremely close to the Sun at perehelion, with the fierce heating resulting in rapid sublimation of its ices and the potential for a bright and long tail. It then becomes well placed in the northern sky and passes about 0.4 AU from the Earth. Comets are notoriously difficult to accurately predict and just about anything could happen – from the comet being destroyed as it swings round the Sun, to it becoming a “Great Comet”, visible with the unaided eye even from urban areas.
James Abbott is an astronomer, NEAS member and CfDS Regional Information Officer.