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Skywatch October 2005by Julene M Packer-JohnsonEclipse season is upon us this month. Venus is the bright star you see in the western sky at sunset. Mars grows bigger & brighter in our night sky as Earth passes close to Mars. Saturn is visible in the morning sky. Mercury & Jupiter are visible in the twilight at the beginning of the month and then drop out of sight. The Moon occults Antares & Spica in different parts of the world. Two meteor showers occur: Draconid & Orionid. The Night Sky in the Northern Hemisphere As the Sun sets into the western horizon, Mercury and Jupiter are right behind at the beginning of the month. They are visible only at twilight. If you manage to find Jupiter very low along the western horizon at sunset during the first few days of the month, it will help you to find Mercury. If you haven’t found Jupiter by the 4th, look for him to the right of a sliver of a 1 day old Moon. On the evening of the 5th, locate Jupiter lower and farther to the right of the Moon than the previous night. See if you can find Mercury just below Jupiter. Both are setting quickly, so you’ll have to be quick! You’ll also need to have excellent viewing conditions because Jupiter falls under the sun’s beams on the 2nd when he lies 17 degrees from the Sun. Jupiter becomes combust on the 12th when he lies 8 degrees from the Sun. Jupiter conjuncts the Sun on the 22nd and will be in cazimi when within 17 minutes of orb. The Sun will then separate from the conjunction and move past Jupiter in our skies. When the jovial giant comes out from under the sun’s beams next month, he will emerge as a morning star. Venus is the first to light up the evening sky, shining brightly. She sets around 8:30 this month. On the evening of the 6th, the Moon will lie below the brilliant Venus. The next night, you’ll notice the Moon has danced on past. Venus covers a lot of sky this month. At the beginning of the month, you’ll notice her among the fixed stars of Libra. Watch as she moves through the constellation Scorpio and heads toward the boundary of Sagittarius. Mars rises around 9:15 at the beginning of October. By month’s end he will rise around 7:00 p.m. Mars is retrograde this month, so his movement against the backdrop of the fixed stars of the ecliptic is backwards or westward. On the 1st, Mars lies just west of Taurus. Instead of heading into that constellation, he turns to head back to the rear foot of Aries the Ram. Remember that the constellations of the zodiac represent the sidereal zodiac and that our ephemeris reflects the tropical zodiac positions that correlate to our seasons. On the 19th, the Moon joins in the night sky. If you haven’t found Mars yet, look for him to be just left of the Moon. Saturn rises around 2:45 a.m. on October 1st. By month’s end, he will rise around 12:45 a.m. Saturn is preparing for a retrograde station in November and will only move about 2 degrees this month. It is not likely that you will detect much movement out of Saturn. On the evening of the 25th, the Moon will be west of Saturn. By the next night, she will pass him up to lie on the east of Saturn. The Night Sky in the Southern Hemisphere Virgo is heading headlong into the western horizon at sunset with Mercury and Jupiter. Mercury sets in the twilight and Jupiter is not far behind. You’ll need to have good viewing conditions to catch a glimpse of these planets before they descend below the horizon. Your best bet on locating them is on the evening of the 4th. Mercury will appear to sit on top of a New Moon and Jupiter will be just above. Venus is the bright star you see above Mercury & Jupiter. She is also the first object to light up the sky at twilight. Venus sets around 11:00 at the beginning of the month and 11:45 by month’s end. The Moon joins Venus on the October 7th. Look for Venus to lie just below the Moon that night. Mars rises around 11:15 p.m. on October 1st. He will rise earlier and earlier each night and on the 31st, he’ll rise around 8:45 p.m. By the end of the month, you can watch the eastern horizon just after sunset for Mars to appear as a brilliant red ‘star.’ The Moon nears Mars on the 18th. By the night of the 19th, she will have passed him up. If you haven’t located Mars by the 19th, look for him just above the Moon at 10:30 p.m. Saturn rises around 4:45 a.m. at the beginning of the month. He rises around 2:45 a.m. on the 31st. Saturn is joined by the Moon on the 26th who dances below him in the pre-dawn skies. Earth’s Close Encounter with Mars on October 29, 2005 at 11:00 p.m. EDT Earth comes very close to Mars this month as she passes him on the inside track around the Sun. On October 1st, when Mars stations retrograde at 6:04 a.m. EDT, his distance from Earth will be 49 million miles. By month’s end he will be 6 million miles closer, reaching a close proximity of 43.1 million miles away on the 29th. While we can’t actually see Mars moving closer, we can observe this by watching him appear bigger and brighter in the sky. When you see a bright red ‘star’ in the night sky that is not twinkling, you’ll know you have located Mars. He will continue to brighten through the first week of November. Keep an eye on Mars; he is the planet to watch this month. When planets beyond Earth are retrograde, it means that we are passing them on the inside track around the Sun. In the middle of this retrograde period, the planet is in opposition to the Sun. The opposition occurs next month on November 7th. The reason that the opposition and the closest pass do not occur on the same date is because of the elliptical orbits of both planets. The alignment is occurring with Earth in the perihelion portion of her orbit (furthest from Sun) and Mars in the aphelion portion of his orbit (closest to Sun), thus bringing the two orbits closer together. The last time Mars came this close to Earth was on August 29, 2003 and that was the big one. Mars came closer to Earth during his last retrograde pass than he ever had in recorded history -- 34.9 million miles. He will not come that close again in our lifetime. However, Earth & Mars are still in orbital positions where we will have a few good close encounters with Mars yet to come, but the closest was 2 years ago. If you’ve been reading Sky Watch that long, you’ll remember. Visibility of the October 3, 2005 Solar Eclipse The annular eclipse occurs at 6:28 a.m. EDT when the Moon conjuncts the Sun and conjuncts the South Node with a 3:18 orb. This is the condition for a Total Eclipse (less than 9:55 orb it must be total, can be total up to 11:15 orb). However the Moon is going to be too small to cover the Sun completely. This produces an annular eclipse, which means that the Moon will pass fully in front of the sun, but rather than covering it completely, we will see a “ring of fire” around her circumference. The solar eclipse is visible on the morning of October 3rd over Spain and Portugal. It will travel southeast through Africa as a partial eclipse. The rest of Europe will also be able to observe a partial eclipse. Please don’t look directly at the eclipse. Visibility of the October 17, 2005 Lunar Eclipse The partial lunar eclipse occurs at 8:14 a.m. EDT when the Moon opposes the Sun and conjuncts her North Node with a 12:34 orb. Therefore the Moon will pass only partially within the Earth’s shadow. In eastern North America you can see the Earth’s shadow begin to fall upon the Moon around 7:34 a.m. EDT. In western North America you can see darkness begin to fall across the moon around 4:34 a.m. PDT. The eclipse ends at 5:32 a.m. PDT which is very near moonset. On the very edge of the west coast and on the Pacific Islands you can observe the entire partial lunar eclipse. On the east coast, the Moon will set before the eclipse is finished. Mechanics of Eclipses, Eclipse Years, Eclipse Seasons, and the Saros Cycle Eclipses occur when the Sun, Earth and Moon align with the Moon’s Nodes. The alignment with the Lunar Nodes is the factor that makes a New and Full Moon become a Solar and Lunar Eclipse. The Lunar Nodes are the points where the Moon’s orbit crosses the Ecliptic Plane, which is determined by the Earth’s orbit around the Sun. As a result, when the Moon conjuncts her North or South Node, it means she is on the same plane as Earth. This happens every 14 days. Also occurring every 14 days is the conjunction or opposition of the Moon & Sun. Yet, in order for an eclipse to occur, both things must be happening at the same time: the conjunction or opposition of the Sun & Moon along with the Moon’s conjunction to her north or south node. These two things stacking up at 14 day intervals are why we always have a Lunar Eclipse occurring with a Solar Eclipse either before or after. Eclipse season simply means that the both conditions are present and eclipses will occur. The New & Full Moon is coinciding with the Moon conjuncting one of her nodes. Eclipse season lasts for 37.5 days. This time frame comes from the fact that when a New Moon occurs within 18.75 days from a nodal conjunction, a Solar Eclipse will occur. This 18.75 day period before and after the alignment adds up to the 37.5 day eclipse season window. Sometimes the conditions are such that a third eclipse occurs, either solar or lunar in one eclipse season. For instance in June of 2002 we had a solar eclipse between two lunar eclipses. In August of 2000 we had a lunar eclipse between two solar eclipses. In both cases all three eclipses occurred within the 37.5 day window of eclipse season. Every 346.62 days the Moon’s North Node aligns with the Sun providing us with an eclipse year. The fact that this number is not the same as our 365.25 day solar year is the reason that eclipse season doesn’t occur at the same time each year in exact 6 month intervals. Because the alignment of the Lunar Nodes with the Sun occurs 18.63 days sooner than the Earth completes a full revolution around the Sun, the Eclipse Season regresses each year. Looking at our last few solar eclipses around this time, we can see this happening. Going back to December 4, 2002 we had an Annular Solar Eclipse. Following that was the Total Solar Eclipse of November 23, 2003. The next year we had a Partial Solar Eclipse on October 14, 2004. This year, October 3, 2005 is an Annular Solar Eclipse. Can you see the eclipse regression? Can you see the regression in the spring/summer eclipse season? Go through your ephemeris and play with this. It will help you understand the eclipse year and seasons. The other thing you may be curious about in regard to eclipses is the Saros Series. If you have Bernadette Brady’s book entitled The Eagle and the Lark, you’ll notice the eclipses I mentioned above are all labeled “South” (pp 348 – 349). This means the Moon’s South Node is involved in the aforementioned solar eclipses. The spring/summer eclipses of those years involved the Moon’s North Node and are labeled “North”. Run a chart in your software for the eclipses and see for yourself. Notice also how the numbers of North and South in the Saros Series appendix table range from 1 – 19 (pp 337 – 351). This number 19 is significant. If you take an eclipse year of 346.62 days and multiply that by 19 you get a total of 6585.78 days. The synodic cycle of the Sun & Moon is 29.53 days. After 223 synodic months, this cycle also reaches that number of days. 223 synodic months of 29.53 days equals 6585.19 days. The two factors do not coincide at any time before that. This is the greater eclipse cycle that Babylonian astronomers noticed. Saros means ‘repeats’ and after 19 eclipse year cycles, the Saros Series starts over at 1 again. This equates to 18 calendar years and 10 or 11 days. The Draconid & Orionid Meteor Showers Peak This Month On the evening of October 8th, watch the area of the sky where the constellation Draco is located. Earth will barely miss passing through a trail of debris left by Comet 21P/Giacobini-Zinner and we may possibly catch a glimpse of a shooting star or two. This is not expected to be a spectacular show at all; it may in fact be a “no show”. Draco is a circumpolar constellation in the northern hemisphere. You can find Draco surrounding Ursa Minor or the Little Dipper. As the skies darken, Draco is located in the north-northwest sky above the Big Dipper. As the earth turns and night marches on, Draco and the other circumpolar stars will rotate counterclockwise. Ursa Major is due north and low along the horizon around midnight, with Draco to the left. Around 4:00 a.m., Draco lies due north, and the Great Bear is to the right. Even if the Draconid shower is nothing to wait for, it is really neat to go out at different times of any night and watch the Great Bear, Little Bear and Draco rotate through the heavens. On the morning of October 21, watch the area of sky where the constellation Orion is located. Remnants of Halley’s Comet will produce the radiants of this shower. This one is better than the Draconids and should produce 5 to 15 meteors per hour. However the bright Disseminating Moon will dampen the display. It will be midnight in the northern hemisphere before Orion has risen fully over the eastern horizon, and you may glimpse a shooting star or two after he gains some more height around 2:00 a.m. You’ll notice the Moon hanging out near the horns of Taurus the Bull just above Orion’s head. The Moon Occults Antares & Spica This Month On October 8th the Moon passes in front of Antares over the central Pacific Ocean, Western Samoa and northwestern South America. On Halloween, the Moon passes in front of Spica over northeast North America. While you are outside passing out candy to neighborhood trick-or-treaters, see how close the Moon comes to Spica where you live. Moon Data for October 2005 The New Moon occurs on October 3rd at 6:28 a.m. EDT and produces a Solar Eclipse. The First Quarter Moon occurs on October 10th at 3:01 p.m. EDT when the Moon perfects waxing square to the Sun. The Moon reaches perigee on the 14th at 9:58 a.m. EDT and will be 227,080 miles from Earth. The Full Moon occurs on October 17th at 8:14 a.m. EDT and produces a Partial Lunar Eclipse. The moon makes waning square to the Sun on the 24th at 9:17 p.m. EDT resulting in the Last Quarter phase. On the 26th at 5:33 a.m. EDT the Moon reaches apogee and will be 251,341 miles from Earth. Sky Maps Available in the OCA Main Public Library Sky maps showing the position of Mercury, Jupiter, Moon & Venus are available in theOCA Public Library. The map of the northern hemisphere is drawn for the evening of October 5, 2005 at 7:15 p.m. The map of the southern hemisphere is drawn for the evening of October 4, 2005 at 8:00 p.m. Sky maps showing Mars, Moon and Orion rising in the eastern sky are available in theOCA Public Library. for the northern hemisphere. The map is drawn for the night of October 19, 2005 at 11:00 p.m. The map of the southern hemisphere is drawn for the night of October 20, 2005 at 3:45 a.m. and due to the slant of the ecliptic, Saturn made it on the page with Mars and Moon. Happy Stargazing & Planet Tracking! Remember not to look directly into an eclipse or to point binoculars or a telescope at one. View safely! Julene Packer, Dipl.O.C.A., ISAR-C.A.P. |
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