SKY WATCH November 1995

by Harry Adams


With the return to Standard Time it is now possible to go out in the evening on a week night, do a couple of hours of serious observing and still be back inside well before eleven o'clock. After the little ones have been safely tucked away in their beds and the chores done up, why not don a parka, grab the November star chart and a flashlight with a red lens, then go outside to learn a few constellations? Go on. You might even enjoy it; fresh air, breeze in your hair, frost bitten fingers. Did I forget to mention gloves and a toque? Oops!

All this talk of learning the constellations has an ulterior motive behind it. A good knowledge of the star patterns is a key step in learning to find your way around the night sky. Every month the Earth advances about 30 degrees in its orbit around the Sun, bringing a new set of constellations up in the east and retiring the previous season's in the west. After a year you should know well over 40 of them. With this kind of familiarity with the night sky, you can now start to make serious observations of meteor showers.

The months of August through January have the three best meteor showers of the year: the Perseids on August 12, the Geminids on December 14 and the Quadrantids on January 3. November, on the other hand, has only three poor showers, which have only one seventh of the strength of the best three. The weakest of November's showers, the Leonids, yields about 12 meteors per hour for a single observer, under ideal conditions.

Every 33 years, however, this poor performer undergoes a startling transformation. An unusually dense cloud of debris accompanies the Leonid's parent comet, P/Tempel - Tuttle. When the comet comes into the inner solar system and rounds the Sun, as it does once every 33 years, the Earth ploughs through this cloud of dust grains and the fireworks start. In 1966 the meteor rate reached one hundred and fifty thousand (150,000) per hour for a single observer! This was not a shower. It was a storm. Previous storms were observed in the years 1799 from South America (30,000 per hour), 1832 from Europe and Siberia (20,000), 1833 from North America (150,000) and 1866 from England and N. America (60,000). The level of activity in the years 1900 (1000 per hour) and 1932 (240) while not up to the title of storm, certainly ranked as best of the year.

The storm phase of the shower, if it occurs at all, only lasts for about an hour and so it is only visible over a limited, unpredictable area of the Earth's surface. Nevertheless, the number of meteors observed does seem to increase dramatically for everyone in the year of the storm and to a lesser degree in the few years before and after the storm. Meteor rates of 100 to 400 per hour have been recorded in these years.

The next chance to catch a Leonid storm will be sometime between the years 1997 and 2000. But don't wait until then. Take a lawn chair out this year and look for a few Leonids yourself. The best time to observe them is on the evening of Friday, November 17. The meteors will come from the east. The point in the sky where meteors appear to originate is called the radiant and it rises about midnight. Light from the Moon will wash out the fainter meteors after moonrise at 2:19h EST on the morning of November 18.

If you want to take things a step further, try counting meteors in hour long time intervals over several nights. This is the sort of data that can be used to plot the density profile of the meteor stream. Another project would involve plotting the paths of the meteors on a star chart and that's where learning the constellations comes in handy. These meteor plots allow the position and motion of the shower's radiant to be determined. This is one area of astronomy where amateurs still do most of the work.

November's star chart is for 21h EST. The chart shows the sky for the middle of the month, looking to the South, from the Horizon (curved line near the bottom) to the Zenith (the point directly overhead, labelled Z on the chart). The directions southeast (SE), south (S) and southwest (SW) are shown on the Horizon line. Brighter stars are represented by larger dots, fainter stars by smaller dots. All times are given in Eastern Standard Time this month.

The Sun rises at 7:10h EST on the Nov. 15 and at 7:30h EST on Nov. 30. Setting times for those dates are 16:38h EST and 16:26h EST respectively.

Venus, Mars and Jupiter are all visible in the southwest at sunset. On Nov. 15, Jupiter will be the highest of the three at 11 degrees altitude. Mars, the faintest of the trio, will be to Jupiter's southeast at 10 degrees altitude and Venus, the brightest, will be three to four times farther away to the southwest at 8.3 degrees altitude. They will perform a little waltz for about a week. By month's end they will be in a line with Venus the most easterly and Jupiter the most westerly.

Saturn shines at magnitude 1.0 in the constellation of Aquarius this month. At sunset, the ringed planet is about 25 degrees high in the southeast and is due south around 20:00h EST.

Moon - FQ November 5, FM November 12, LQ November 19, NM November 27

References: Handbook for Visual Meteor Observations, Paul Roggemans, Ed., Sky Publishing Corp. Burnham's Celestial Handbook, R.Burnham, Jr., General Publishing Co., Toronto. The Observer's Handbook of The Royal Astronomical Society of Canada, edited by Roy L. Bishop, University of Toronto Press Incorporated.


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