October 2008
Skywatcher’s Guide for October 2008
PLANETS
HIGHLIGHTS: The two normally brightest planets, Venus and Jupiter, can now be seen glimpsed with the unaided eye in bright evening twilight. Although presently far apart in the sky, the two will gradually move closer, towards their wonderful grouping next month on November 30. Also, Venus passes almost 3 degrees north of the bright star Antares, the Rival of Mars, on October 25-26.
Bright Jupiter dominates the southern sky in October for a few hours after sunset, especially during the first half of the month. Jupiter appears one hour after sunset as a very bright, almost brilliant white star-like object, well above the southern horizon in early October, but moving toward the southwestern horizon in the latter half of October. On October 1 Jupiter is still bright (brighter than magnitude -2.3) and large in a telescope (40 arc seconds), though by October 30 has faded somewhat (to magnitude -2.2 and 37 arc seconds) from its brightest and largest back in July. October (especially early in the month) continues to be a very good time to view the giant planet this year in twilight and for an hour or two after twilight ends. Look for bright, whitish Jupiter just east (or roughly ‘left’) of the Teapot of Sagittarius: It’s the brightest star like object well up in the evening sky in October. Jupiter is highest and due south in bright evening twilight in early October (at around 30 degrees in altitude for much of the Desert Southwest, 34 degrees for southern Arizona) but after twlight ends continues to lose altitude in the southern sky each night this month. Look for the waxing gibbous Moon to be slide below (and west) of Jupiter in the southern sky on Monday evening, October 6.
When looking at Jupiter in a telescope to view its cloud belts and festoons, the sharpest views should be just after sunset in evening twilight, when at or near its highest in the twilight sky this month. As with any planet viewing is dependent on atmospheric stability and conditions, and of course, the quality and size of the telescope used. However to view its moons, a good pair of binoculars is all that’s needed. Jupiter sets in the south-southwest around 11:30 p.m on October 1, around 10:45 p.m on October 15 and around 10:00 p.m. in late October.
The brilliant planet Venus continues to move out of the glare of the Sun above the western horizon and into the evening twilight this month. White Venus is the brightest star like object normally ever seen in the sky. Venus starts October about 7 degrees above the west-southwestern horizon about 45 minutes after sunset, and creeps higher each evening, reaching 13 degrees above the southwestern horizon at that time by October 31. Look for Venus just only 3 degrees from Antares, the brightest star in Scorpius, the Scorpion on October 25-26 (the two are within 4 degrees apart on October 24 and 27). Also, the razor thin 3 day old waxing crescent Moon is barely visible and not far from Venus this month (but well below and south of it) near the horizon on Wednesday evening, October 1. A second 3 day old crescent Moon this month is slightly closer to Venus, below it and near the southwestern horizon on October 31.
Saturn rises earlier and creeps higher above the eastern horizon each morning this October. Look for Saturn in the morning twilight well above the eastern horizon as a slightly brighter than 1st magnitude star-like object, 90 minutes to one hour before sunrise. In early October Saturn is over 10 degrees above the eastern horizon, one hour before sunrise but by late October climbs to over 30 degrees in altitude at that time. Saturn is found in the constellation Leo the Lion, far below its bright star Regulus, The 25 day old waning crescent Moon is found above Saturn in our sky on Saturday morning, October 24 and closest to Saturn but below it on October 25.
The elusive planet Mercury rockets out of the glare of the Sun and into the dawn twilight, not far above the east-southeast horizon. It is brightest and best visible starting about one hour before sunrise from October 20-29, with Mercury brightening gradually during the period, reaching magnitude -0.8. After October 29 Mercury noticeably sinks toward the horizon, but remains bright. Also, the thin waning crescent Moon is found rising closest to Mercury and above it on Monday morning, October 27, starting one hour to 50 minutes before sunrise (at 5:45 a.m. from southern and central Arizona).
Faint Mars is now lost in the glare of the Sun until it reappears as a dim object in the December morning sky.
Visitors to Flandrau’s 16-inch telescope should note that only the planet Jupiter is visible this month in the telescope after it opens at 7 p.m. The telescope normally closes at 10 p.m.
Finally, remember that in spotting planets there is a general rule: ’stars twinkle, planets don’t’. This is because stars are point sources of light; therefore starlight is easily disturbed and shifted by air currents in the Earth’s atmosphere. However when looking at Mercury right now, note that it may appear to twinkle somewhat; however, this twinkling is of a slower nature than the bright stars.
OCTOBER STARS
Overhead anywhere in the U.S., at the end of evening twilight, stargazers can find the bright stars of the widely spaced triangle Summer Triangle: Vega, Deneb, and Altair. In October the Summer Triangle slowly loses altitude and sets in the western sky after midnight. Vega, Altair, and Deneb are each the brightest stars of three constellations that make up the Summer Triangle. Vega is the brightest star in the small constellation of Lyra, the Lyre (a small ancient harp). Vega, one of the closer stars to Earth (only 25 light years away), was the Pole Star (our North Star) some 12,000 years ago, and will again be the North Star in 12,000 A.D. when Earth’s cyclical wobbling motion brings in near the pole once more. Deneb is the tail of Cygnus the Swan, but also marks the bottom of the cross-shaped pattern whose other name is the Northern Cross. Deneb is a huge supergiant star over 1,600 light years from Earth. Aquila, the Eagle is the home of the bright star Altair, the first star of the three in the triangle to set late at night and the closest of the three to Earth at only 16 light years distant. Aquila looks more like a diamond or kite than an Eagle. Aquila and Cygnus (or the Northern Cross) mark some of the brightest areas of the northern Milky Way, which is prominent in dark skies on Moonless October nights.
Taking center stage in October is the Great Square of Pegasus. Find the Great Square quite a ways up from Fomalhaut, the bright star marking the Southern Fish, which lies somewhat low in the south. Alpheratz, the eastern corner star of the “Great Square” of Pegasus, is also the head of Andromeda, the Chained Lady or Princess. In Andromeda, is the “Great Andromeda Galaxy”, M31, which can be viewed as a fuzzy spot in binoculars. Rising in the eastern sky (and far from M31) is the Seven Sisters (or Pleiades) star cluster, a wonderful sight in binoculars.
Orionid Meteor Shower Spoiled By Moonlight
The Orionid Meteors, which peak in the pre-dawn hours of October 20, 21 and 22, are washed out by the gibbous to last quarter moon, which will dim the shower with its bright light. Meteors gazers will need to wait until December for this year’s Geminid meteors (on December 13/14) for a major meteor shower unhindered by bright moonlight.
MOON PHASES
The October first quarter Moon will occur on Monday evening, October 6. The October Full Moon can be called the Hunter’s Moon rises on the evening of Tuesday, October 14 and sets on the morning of Wednesday, October 15. The October last quarter Moon occurs on Tuesday morning October 21. The October 2008 new moon will occur on Tuesday, October 28.
Note: Additional information can be accessed by phone at Flandrau Science Center’s Astronomy Newsline at (520) 621-4310 or as a menu option at 621-S-T-A-R.
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