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Skywatch September 2005by Julene M Packer-JohnsonAs the sun sets on September 1st, watch for Venus & Jupiter to appear in the western sky. They are a fascinating pair to observe this month as they make conjunctions with fixed stars. Mars will rise later in the evening. Mercury and Saturn are morning planets this month, though Mercury is only visible until about the 9th. The sun reaches the intersection of the Ecliptic and Celestial Equator on September 22nd. The Venus - Jupiter Dance in the Northern Hemisphere As the sun sets, look to the western horizon for two bright Œstars‚ to appear in the twilight. These will be the planets Venus & Jupiter. Venus is lower to the horizon and will be brighter than Jupiter above. As the sky darkens more, the star you see pop into view to the left of the pair will be Spica, the brightest star in the constellation Virgo. The pair of planets will set around 9:15 p.m. at the beginning of September. Venus, being closer to the sun than Jupiter will move faster through the zodiac. If you‚ve been watching this dance since last month, you will have already notice her gain on Jupiter. She will conjunct Jupiter on the 2nd. After which, she will pass by Jupiter & Spica on her direct eastern trek along the ecliptic as she enters the constellation Libra. On the evening of the 5th, Venus will conjunct Spica and lie above the fixed star. Jupiter will be to the right. The Moon joins the duo on the evening of the 6th. Jupiter will conjunct Spica on the 24th. However, by this time, Spica will set around 7:50 p.m. and Jupiter will set around 8:00 p.m. so it will become difficult to watch the jovial giant. Venus remains in the evening sky until around 8:45 p.m. when she dips into the western horizon. The Venus ˆ Jupiter Dance in the Southern Hemisphere At the beginning of September, Venus & Jupiter will pop into view high above the western horizon as sunset darkens the skies. They will appear side by side on the evening of the 1st and set around 10:00 p.m. Watch on the following days as Venus pulls east of Jupiter and appears higher in the evening sky. On the evening of the 7th, the Moon joins Jupiter & Venus in the night sky and will actually pass in front of Venus blocking her from view in some areas of the world. If you are in southwest Africa or Antarctica, you can witness the occultation of Venus. As the month progresses Venus will enter the constellation Libra. You can watch her pass by the fixed star Zubenelgenubi on the evening of the 24th. By month‚s end, Jupiter will set around 8:30 p.m. near the fixed star Spica of Virgo and Venus will set around 10:45 p.m. after Zubenelgenubi and Zubeneschamali of the constellation Libra. Mars in the Evening Sky in the Northern Hemisphere At the beginning of September, Mars will rise around 11:00 p.m. in the constellation Aries. Mars is close to Earth in his orbit and brighter than usual. Mars will appear as a red star that is not blinking. By month‚s end, he will rise around 9:30 p.m. and visually lie between the stars of Aries & Taurus. On the evening of the 22nd, the moon joins Mars in the evening sky. The moon should begin to rise over the eastern horizon by 9:30 p.m. Watch for Mars to rise about a half an hour later. Mars in the Evening Sky in the Southern Hemisphere At the onset of September, Mars will rise around 12:45 a.m. By month‚s end he will rise around 11:20 p.m. Mars is traveling between the fixed stars that outline the constellations Aries and Taurus. In the wee hours of the morning on the 22nd, you will notice the Moon above Mars. By the 23rd, she will dance on by to hang below the red planet. Mercury in the Pre-Dawn Sky in the Northern Hemisphere Mercury rises around 5:45 a.m. not long before the sun. It will be tricky to locate him along the horizon unless you have very dark skies. If you see two objects in the pre-dawn sky as dawn encroaches, you have also located Regulus, the alpha star of the constellation Leo. Mercury will be above Regulus. If you locate Mercury, then you can watch as he conjuncts the fixed star on the 4th. By the morning of the 5th, Mercury will be below Regulus in the pre-dawn sky and will rise around 6:00 a.m. By the 9th Mercury will rise at about 6:30 a.m. and will no longer be visible. On the 17th at 11:00 p.m. EDT, Mercury will reach superior conjunction to the Sun. The inner planets can not possibly travel far enough away from the sun to oppose it. Astronomically, there are two types of conjunctions that occur between an inner planet, Earth & Sun. When the inner planet is conjunct the Sun and Earth in between the Sun and Earth, it is called an inferior conjunction. The inner planet passes directly between Sun & Earth. The superior conjunction we experience with Mercury this month is the result of Mercury being in conjunction with Earth & Sun from the opposite side of the sun. In other words, the Sun is in the middle of the superior conjunction. Mercury in the Pre-Dawn Sky in the Southern Hemisphere Mercury rises around 7:20 a.m. and is quickly followed by the Sun. You will be lucky to catch a glimpse of him this month. Saturn in the Morning Sky in the Northern Hemisphere Saturn is currently traveling among the fixed stars of the constellation Cancer. He will rise around 4:15 at the beginning of the month and 2:45 by month‚s end. The moon joins Saturn on the 28th. Saturn is the dimmest of the visible planets right now and will lie to the right of the moon. Saturn will be brighter than Pollux & Castor, the heads of the Gemini Twins, who lie above him, or west, along the ecliptic. However the fixed star Procyon of Canis Minor is brighter than Saturn. Canis Minor lies below the ecliptic and the constellations of Gemini & Cancer. As those constellations rise perpendicular to the horizon, Procyon and his constellation appear to the right of the ecliptic. Saturn in the Morning Sky in the Southern Hemisphere Saturn rises around 6:30 a.m. at the beginning of the month among the dim stars of the constellation Cancer. By month‚s end he will rise around 4:45 a.m. With the tilt of the ecliptic being different from the northern hemisphere, Procyon of Canis Minor lies well above Saturn in your pre-dawn sky, while Castor & Pollux of Gemini lie to the left. The Moon joins Saturn on the 28th. That morning, look for a Œstar‚ that is not blinking to the right of the moon. That will be Saturn. The Autumnal Equinox On the 22nd at 6:23 EDT, the sun ingresses into tropical Libra. This means the day of equal day & night is upon us and a new season officially begins. In order to understand just exactly what causes the equinox, you have to be familiar with two great circles: the Ecliptic Plane and the Celestial Equator. The Celestial Equator is the earth‚s equator extended into infinite space. The Ecliptic is of course marked by the band of zodiac constellations. However, the constellations do not decide the Ecliptic, but rather the apparent path of the Sun, which in all actuality is caused by the tilt of Earth on her axis as she rotates and revolves around a fixed Sun. The Ecliptic Plane has a 23.6 degree tilt above and below the Celestial Equator. There are two very important points where these two great circles intersect: 00 Aries in the east & 00 Libra in the west. If you imagine a globe with a circle around the equator and then pass another circle at a 23 degree tilt through that circle, you will note two intersections occur on the celestial equator. At these two points the declination (measured north and south of the celestial equator) is 00 degrees. At the eastern intersection the celestial longitude (measured along the ecliptic) is 00 degrees or 00 Aries. At the western intersection the celestial longitude degree is 180 or 00 Libra. When the Sun reaches the western intersection of these two great circles, fall begins in the northern hemisphere & spring begins in the southern hemisphere. The declination is considered to be 00 South because the Sun is heading south to the Capricorn solstice. Don‚t forget there are only two times a year when you can balance an egg on end on your kitchen counter. This equinox is one of them! Provides interesting food for thought on expanding the perception of „as above, so below‰ doesn‚t it?! Moon Data for September 2005 On September 3rd, the moon conjuncts the sun at 2:45 p.m. EDT resulting in a New Moon. The faster moving luminary then pulls away from our parent star to illuminate the angular phases of their relationship. On the 6th, a Crescent Moon will join Jupiter in the evening sky. On the 7th, the moon joins Venus in the evening sky. This is an occultation for observers in southwest Africa and Antarctica. The First Quarter Moon occurs on the 11th at 7:37 a.m. EDT when the moon reaches an angular separation of 90 degrees from the sun, or a waxing square. On the 16th, the moon comes closest to Earth as she can in her orbit. This month‚s perigee distance is 223,945 miles. The Full Moon occurs at 10:01 p.m. EDT on the 17th, when the moon opposes the sun. September‚s Full Moon is the Harvest Moon. On the 22nd, the moon joins Mars in the night sky. The Third Quarter Moon occurs on the 25th at 2:41 a.m. EDT. This phase of half illumination is representative of the 270 degree angular separation of the moon from the sun, or the 90 degree waning square. On the 28th, the moon reaches the farthest distance from Earth in her orbit. This month‚s apogee distance is 251,846 miles. Also on the 28th, the Moon joins Saturn in the morning sky. Sky Maps Available in the OCA Main Public Library Sky maps for September are available in the OCA Main Public Library to help you identify the constellations and locate the planets. You will find evening sky maps of Venus, Jupiter and the Moon. The map for the southern hemisphere is for the evening of September 6th at 8:30 p.m. The map for the northern hemisphere is for September 7th at 8:30 p.m. You will also find morning sky maps of The maps of Moon, Mars and Saturn. The map of the southern hemisphere is for September 23rd at 5:30 a.m. The map for the northern hemisphere is for September 24th at 3:15 a.m. Happy Stargazing & Planet Tracking! Julene Packer, Dipl.O.C.A. |
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