Vega and Deneb will rise as pole stars

Vega, Deneb and Altair are the stars that make up the asterism known as the Summer Triangle. Two of these stars, Deneb and Vega, have another distinction in that they are, or will be, the pole star.

Today we all know the pole star is Polaris in Ursa Minor, but this has not always been, nor will it remain, the case. Around 3000 B.C. Thuban in Draco the Dragon was the pole star before it switched to Polaris. Around A.D. 9000 Deneb in Cygnus the Swan becomes the pole star followed by Vega, the brightest of the pole stars, around A.D. 14,000.

Why does the pole star change? The Earth wobbles on its axis as it spins, a phenomenon called precession, and the axis of rotation traces out a small circle in the sky pointing to various “pole” stars in the process. This process requires 25,800 years to complete one circle. It takes around 2,150 years to change by 30 degrees, one house or sign of the zodiac, and this is why the astrological sign the sun enters each month is different from the true astronomical position.

Focus on the planets

November has three planets gracing the east-southeast about an hour before sunrise. In a diagonal line rising from left to right are, from the horizon, Mercury, Venus and Saturn.

Mercury puts on one of its best pre-dawn shows of the year, rising in the east about an hour and a half before sunrise. Look for Mercury low on the horizon with the bright star Spica to its immediate right. The elusive inner planet will be in view until around midmonth.

Venus returns to the pre-dawn sky as the brilliant “Morning Star.” Look for Venus prominent on the southeastern horizon about an hour and a half before sunrise, where it cannot be mistaken for anything else.

Mars rises in the east around 8:30 p.m. as November opens. The Red Planet increases in brightness throughout the month, outshining all the stars but Sirius in the winter sky. Mars lies among the stars of Gemini with the twins Castor and Pollux to its lower left. Note that Betelgeuse, the red giant star situated to the right of Mars in the shoulder of Orion, is the same color and rises at the same time as Mars and could be mistaken for the reddish-orange planet.

Jupiter is low in the southwest at sunset and continues to sink toward the horizon during the month. Because of Jupiter’s proximity to the horizon, atmospheric distortion will make surface features difficult to see, however, its four major moons should be easy to spot.

Saturn is very high in the southeast about an hour before sunrise situated among the stars of Leo. Viewers hoping to see Saturn’s fabled ring system with a telescope will be disappointed as they are as near to being edge-on as they have been in a decade.

Neptune in Capricornus and Uranus in Aquarius are well situated for viewing on the southern horizon shortly after sunset. Use the finders charts in the July 2007 issue of Sky & Telescope to spot these far distant planets.

November events

1 Sunrise, 7:13 a.m.; sunset, 5:24 p.m. Moon in last quarter, 4:19 p.m.

5 The waning crescent moon is to the immediate right of Venus in the pre-dawn sky.

7 If you are up to view the pre-dawn southern horizon, Spica is to the lower left of a thin crescent moon with Mercury to the immediate left of the bright star.

9 New moon, 6:03 p.m. The moon is at apogee or farthest distance from Earth today and, in fact, at its most distant point from the Earth for the year.

12 The waxing crescent moon is low in the southwest about an hour after sunset with Jupiter shining to its upper right.

17 Moon in first quarter, 5:32 p.m.

18 This is the peak evening for viewing the Leonid meteor shower that originates from the head of Leo the Lion. Leonids are swift, bright, and often leave persistent trails. Look for 20 to 40 meteors an hour with the low position of the moon making for a favorable dark background.

22 The sun enters the astrological sign of Sagittarius but astronomically is just leaving Libra.

23 The sun enters Scorpius on the ecliptic.

24 Full moon, 9:30 a.m. The full moon of November is called the Frost Moon or Beaver Moon. The moon is at perigee or closest approach to the Earth and the combination of these two events may lead to abnormally high tides.

26 Look for the moon and bright reddish-orange Mars very close together around 9 p.m. in the east-northeast.

30 The sun enters Ophiuchus, not one of the traditional houses of the zodiac, on the ecliptic. Sunrise, 6:51 a.m.; sunset, 3:57 p.m.

Send astronomical queries to Clair Wood at cgmewood@

aol.com or care of the Bangor Daily News, Style Desk, P.O. Box 1329, Bangor, Maine 04402.