What's Up in the Sky - October 2010

Fred Barrett | Sep 30, 2010

By Fred Barrett

Nights are cooling off now and darkness is falling much earlier. Speaking of fall, I have written before that it is the best time of the whole year for astronomy. You don’t have to wait up late for a dark sky and there are few or no bugs to torment you. Also, some of the spectacular summer constellations are still in the sky and readily available for your viewing pleasure. Review some of my summer columns and go out and have another look. Look in the summer triangle area. Its three constellations, Cygnus, Lyra and Aquila, are up there in all their splendor. Note that they have shifted more to the western horizon. Another advantage to early darkness is that you can take the younger kids out and give them a good look at the sky and still get them to bed at a decent hour. Make it an outdoor adventure. See who can find the brightest stars or maybe the reddest or bluest ones!

This month I want to talk about the Northern Lights. A really fine show is anticipated this fall. The phenomena’s proper name is Aurora Borealis in the northern hemisphere. Standing upside down in the southern hemisphere we would know the lights as the Aurora Australis. Look at the image included with this column. It’s a picture I took during the last good aurora season and you can clearly see the rippling light show in the sky above my observatory. The aurora is caused by particles in the solar wind following Earth’s magnetic field lines and colliding with oxygen and nitrogen atoms about 80 kilometers high up in Earth’s ionosphere. A photon of light is emitted and its colour depends on whether it collided with oxygen or nitrogen and how high in the ionosphere it occurred. The lights appear as east-west curtains lined up with the Earth’s magnetic field lines.

Auroras occur more often near the equinoxes. Science does not yet have a full explanation for why this happens. It has something to do with the tilt of the Earth and its alignment with the interplanetary magnetic field. Fall equinox occurred September 22. They also peak at a period of maximum sunspot numbers. The Sun has an 11-year sunspot cycle and it is now on the way towards its maximum sunspot numbers. The solar maximum, however, is somewhat unpredictable. It was expected in 2010/2011 but now may be as late as 2013. As the maximum approaches, the number of solar flares increase and more coronal mass ejections (CME), massive bursts of solar wind, happen in the Sun’s atmosphere (corona). The resultant solar wind shock waves hit the Earth’s magnetic field and create conditions for more spectacular auroras and lots of them!

For those of you with computer access look at this website: http://www.asc-csa.gc.ca/eng/astronomy/auroramax/default.asp or this one: http://www.tgdaily.com/space-features/51635-northern-lights-to-be-streamed-nightly-online.

It’s fascinating to discover that Earth’s auroras have been viewed from above its atmosphere and photographed from space. Note that aurora have been viewed on other planets in our solar system: Mars, Venus, Saturn and especially Jupiter.

Jupiter is just past its closest approach to Earth (September 21) and dominates the sky through most of the night. You can find Uranus within two degrees of Jupiter in a small scope. If you are up for a planetary hunting trip, pull out a star chart and search for Neptune high in the south shortly after dark.

Another comet is gracing our skies near the constellation Cassiopeia. I wrote about that constellation last month so it should be fresh in your mind. The comet is passing by the bottom of the ‘W’ during the first week of October and continues on to the northeast and through the constellation Auriga during the rest of the month. It is a short period comet coming back every six years and was only discovered 24 years ago. Why was this comet not discovered sooner? After all, it’s visible through binoculars most everywhere and even faintly visible by eye at a dark sky site. It seems that it had three close encounters with Jupiter that shifted its orbit closer to the sun. Before that it remained more than two AU from the sun (one AU is Earth’s distance from the sun ~93 million miles) and hopelessly invisible to all. It will be a very nice view through binoculars.

The full Moon this month is on October 22 and is called the Hunter’s Moon. I can hear duck hunters shooting away as I write this sentence! The waxing gibbous Moon is a nice sight above Jupiter on the evening of the 19th. If work or your habits get you up early in the morning, go out about one hour before dawn on the 25th and you’ll have a pretty view of the moon passing very close, within two degrees, of the Pleiades cluster.

There are two meteor showers this month. On the 8th, there is the Draconid shower and on the 21st, the Orionids. Neither are large showers but if you go out, you should expect to see a modest increase in the number of meteors, with occasional bursts in activity.

“The Beginner’s Observing Guide” by Leo Enright is available at the Sharbot Lake Pharmacy or it can be ordered from the Royal Astronomical Society of Canada at www.rasc.ca/publications. SKYNEWS, our national Canadian astronomy magazine, is available at store magazine racks or a subscription can be ordered at the RASC website above. Note that it has a detachable centerfold star chart.

If you have questions or suggestions, Fred Barrett may be contacted at This email address is being protected from spambots. You need JavaScript enabled to view it.

The Beginner’s Observer’s Guide by Leo Enright is available at the Sharbot Lake Pharmacy or by contacting the Royal Astronomical Society of Canada www.rasc.ca/publications, subscriptions for our very own excellent Canadian astronomy magazine, Sky News, are also available from RASC..