Almanac for October 2012
Is it always ‘darkest before the dawn’? Hold that thought, while we celebrate October as one of the best months for astronomy! Sunset comes earlier, even with DST still in effect sunset moves up from about quarter of seven to around six pm by the end of the month. So there is plenty of time after work to enjoy dark skies while most of us come home in daylight. The morning darkness, with some of the latest sunrise times of the year, is disconcerting to most people, but we have a head start on the star-packed winter skies. Now the morning dark overlaps the time many of us start our days, so viewing the sky is a sport that can be enjoyed from outdoor train, subway and bus platforms. Even now, I can step outside when we first get up on a clear, fall morning, and see our two brightest planets against the backdrop of the winter stars and star clusters high in the sky. There appear to be so many stars then, as if proving that it really is ‘darkest before the dawn’. At least that’s true in our modern era, as the light pollution from businesses, traffic and buildings is least in the early morning hours.
Have you ever wondered what a moon of Venus would look like from Earth? Venus, the brightest object in the morning sky in early October, is very near the bright star Regulus from September 29th through October 7th. On the morning of the 3rd, Venus gets within 0.2 degrees from Regulus. According to an on-line trigonometry calculator, at Venus’ present distance of 99 million miles from Earth, a moon 0.2 degrees away from Venus as seen from Earth would be about 345,000 miles from Venus (about fifty percent more than our Moon’s distance from Earth). So you can imagine Regulus as if it were a Moon of Venus. Get out there on the morning of the 3rd and see what it looks like – with and without optical aid. Then go and check out how the Earth and our Moon look from the next planet out, Mars, at http://hirise.lpl.arizona.edu/earthmoon.php , or the Solar System Simulator site. Then think about what effects a noticeable moon of Venus would have made on science and mythology on our planet.
Meanwhile, Venus is waxing past 3/4 full but getting smaller overall, down past 14 arc seconds, making it hard to get a good photo of the slightly out of round planet. But Venus will be out there greeting us as the morning star right through into the new year. While you’re out, look up, way up, and there will be Jupiter, swelling past 44 arcseconds wide. Check out the changes in the Jupiter’s belts. Which belt is larger now? – It’s different from last year’s arrangement. It’s great that these changes are visible in most telescopes, so check Jupiter every few days.
So, what do we have in the evening sky? Saturn is bowing out into the sunset, soon to be seen only on the SOHO solar observatory C3 telescope as it passes in back of the Sun from our point of view. Mercury slides out from the Sun, but so low in the evening sky, it’s hard to catch without binoculars. Mars is still staying ahead of the sunset, passing by its ‘rival’, the star Antares, but it’s harder to see the resemblance because they are so low, so soon after sunset. But get a clear southwestern horizon and see for yourself. Binoculars can help.
If you can stay up later and don’t mind a wavy picture in your telescope like an old-fashioned analog TV tuned to a distant station, Jupiter and it’s escort, Aldebaran, soar over the horizon north of east after 10pm in early October, but as early as 8pm in late October, making an impressive entrance visible without optical aid.
Going deeper, Vesta and Ceres, targets for the Dawn space probe, are well placed in the morning sky to the east of Jupiter and will go from magnitude 8 to 6 ½ (Vesta) and 9 to 7 ½ (Ceres) as the year ends. Uranus (mag 5.7) and Neptune (7.9) get higher in the evening sky, becoming better to see as the evening advances. Having a sky version of AAA routing maps can help find these worlds.
The Orionid meteor shower, fragments of Comet Halley, puts on a modest show, punctuated with bright fireballs in the midnight and morning skies, peaking around the 21st.
Our Moon finds itself nearing Mars, low in the evening sky, on the 17th; posing with Mars and anti-Mars Antares on the 18th. The Moon plays in Jupiter’s neighborhood in the sky on the 5th and 6th, makes the scene with Venus on the 12th, and a new moon hides near Mercury on the 16th. Telescopic viewers of the Moon have Luna high in the morning sky as the sunset shadow crawls across its face for several mornings centered on the 6th.
The International Space Station is visible in the morning sky through the 6th and then returns to the evening sky from 8th onward. Tiangong, the Chinese space station, has bright overflights in the mornings from the 14th onward. Check heavens-above.com for times for your location!
See westchesterastronomers.org for the full newsletter and details on our meeting Friday, October 5th.