Night_skies_nov07

Jeff Green | Aug 31, 2006

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TheNightSkies of November, 2006:Leonid Meteor Shower

by Leo Enright

In the month of November, weather permitting, we have more, and longer, chances to observe the autumn skies without having to “stay up too late”, as we did during the summer. In early November, locally, sunset occurs a few minutes before 5 p.m. Eastern Standard Time, and astronomical twilight lasts until about 6:30 p.m. EST. Morning astronomical twilight does not begin until 5 a.m. with sunrise about 6:45 a.m.. By November 30, our nights are about an hour longer than they were at the beginning of the month, because, sunset occurs about one minute earlier per evening and sunrise about one minute later per morning. Therefore, by November 30, the sunset time is about 4:30 p.m. with the end of twilight being about 6:15 p.m., and morning twilight begins at 5:30 a.m. with sunrise at about 7:20 a.m.

In the after-dinner hours of November, the Milky Way sweeps overhead from northeast to southwest. Remember, as you see it emerge into view in the darkening evening twilight, that this great “river of light” is from the many millions of stars in our sun’s home galaxy, with our own Sun being just one of those millions of stars, in fact, one of those “more than 200 billion stars”. Looking in the eastern sky to the right of the Milky Way on any clear November night, we can easily see two prominent constellations: one of them a huge square that may remind us of a baseball diamond with home-plate at the bottom, and one a horizontal row of stars going from the left corner, or ‘third-base side of the square’, back toward the Milky Way. The Great Square was Pegasus to our ancestors, the outline of a flying horse, and the row of stars on its left side was Andromeda, the ‘damsel in distress’ in the classical myth involving Perseus and his rescue mission to save Andromeda. Perseus himself is represented in the constellation by that name, located immediately to the left of Andromeda, and a careful, regular observation of its stars will show one of its brightest stars changes in brightness on a very regular cycle every two to three days – something that some of our distant ancestors saw as the blinking eye of the snake-haired Gorgon held up by Perseus to slay the sea-monster threatening Andromeda. Below the flying Pegasus, that sea-monster, known as Cetus, is there, too, in the southeastern November sky, appearing to sprawl in its death-throes, having just glimpsed the horrid Gorgon. The fifth and sixth characters from that story are there in the sky also: the father and mother of Andromeda. The Queen Cassiopeia is easily recognized above Perseus, even though modern eyes tend to see a large letter “W” on its side in the November sky, rather than a queen seated on a throne. Above the queen is Andromeda’s father, King Cepheus, also an arrangement of stars that the modern eye sees differently, as a five-sided drawing of a house blown over in the wind, rather than a king seated on his majestic throne. Remember that this ancient story can be an excellent reminder for us to look for, and identify, all six of its constellations.

During November, none of the five bright, ‘naked-eye’ planets can be seen in the early evening – something that rarely happens. However, I still hope frequently to see Uranus and Neptune in the evening sky, using my binoculars, as I have for the past four or five months. Because these two planets can be seen only with binoculars or a telescope, among thousands of stars that are similarly faint, describing their location without the aid of a detailed star map is very difficult. Saturn rises in the east at about midnight in early November, and even before midnight in late November. This planet will be particularly easy to locate at any time after midnight on the nights of November 12 and 13; on the 12th, the Last Quarter Moon rises just above Saturn, and the following night the moon is just below Saturn, providing a good lesson in how far across the sky the moon moves in 24 hours. During the whole month, Saturn appears not far from the star Regulus, brightest star in the constellation Leo, the Lion; in fact, it appears only about 5 degrees (or half the width of a fist held at arm’s length) from that star. Venus, Jupiter, Mars, and Mercury are all very close to the direction of the sun, as viewed from planet Earth, this month, and so few people will see them, though possibly a few “early risers” may catch a glimpse of Mercury very low in the east for 10 minutes or so beginning about 40 minutes before sunrise, during the last week of the month.

Some serious astronomers, however, will be concerned about seeing Mercury this month under quite unusual circumstances. For a period of about five hours on November 8, an event called a Transit of Mercury occurs. It is similar to the Transit of Venus that occurred in June 2004. At the times of the Transits of these two planets, they may be seen crossing the face of the sun. How rare are such events? Quite! Transits of Mercury occur only13 times per century; Transits of Venus occur only13 times per millennium! I expect that relatively few people in this area will see the event because few will have the proper and safe equipment to look at the sun while the Transit is occurring. Observing such transits always involves looking directly at the sun, and one should NEVER look directly at the sun, and especially NEVER look at the sun with binoculars or a telescope, unless you are absolutely certain that you have a proper, approved solar filter correctly mounted on the instrument. NEVER use smoked glass, multiple sun glasses, or any such home-grown concoctions! The situation is the same as for viewing a solar eclipse. For viewing solar eclipses and for the viewing the Transit of Venus in June 2004, the use of #14 arc welders’ glass provided a safe “non-telescopic” means of looking at the solar disk. However, for this event, we must remember that Mercury is much smaller that Venus appeared in 2004, and it is much farther away from Earth than Venus was, and so it is just too small to see using the “arc welder’s glass” method. For the astronomers who have the properly approved equipment, the transit begins at 2:12 p.m. EST. In Canada, only those living in western British Columbia will be able to see the whole event, since elsewhere the Transit will end well after the sun has set. Locally the sun sets at 4:45 p.m. EST, allowing local serious astronomers a chance to view the first half of the event, IF they have the proper equipment and the weather cooperates and they have a good view of the sunset point on the horizon.

A very famous meteor shower reaches its peak this month. It is the Leonid Meteor Shower, so named because the stars appear to fly out of the constellation Leo, the Lion. These are the fastest of all the many meteor-shower members with the particles travelling at an incredible 71 km/sec! The pre-dawn hours beginning about 2:30 a.m. on November 17 and 18 are the very best times for observing these “shooting stars”. I would be interested in hearing about the numbers seen per hour. Several years ago this shower provided me with the greatest meteor spectacle I have ever witnessed.

More observing information is readily available in the book The Beginner’s Observing Guide now on sale at Sharbot Lake Pharmacy. Use and cherish our clear, unpolluted skies!