StarWatch: Moravian College Astronomy

OCTOBER 2013

OCTOBER STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

Print Large Sky Charts For 10 p.m. EDT: NORTH | EAST | SOUTH | WEST | ZENITH

Current Solar X-rays:
Current Geomagnetic Field:

Current Moon Phase

Introducing Moravian College Astronomy, Fall 2013: Left to right far back row: Akul Y. Patel, Nick Billera, Tim Smith, Jeremy W. Rigotti, (machine) Ian P. Murphy (red), Joe E. Nehme, Tim S. McGorrey, Kevin D. Weaver, Justin Kiefer, Matt J. Mitchel,... Left to right middle and front rows: Steve C. Scordo, Dillon Hoffman, Brianna A. Wright, Wendy Kay Kunkel, Ashlyn R. Petrie, Michael Giacoumopoulos, Amber L. Weaver, Mackenzie E. Nolan, Sophia H. Osbourne, Gary A. Becker (instructor), Peter K. Detterline (instructor-tie), Chris Aquayo, Nick J. Robertson, Dan V. Sanzo… Missing, Jason F. Boccuti… Gary A. Becker photography in the Boyertown (PA) School District Planetarium, Peter K. Detterline, director...

894 OCTOBER 6, 2013: Venus and the Moon Together Again: In astronomy it can be honestly said that what goes around almost always comes back around. The sky is full of repeating patterns, and early sky watchers mastered these designs and brought order to the heavens as well as to the Earth in the form of calendars and other timekeeping devices. They regulated agriculture, government, and religion. On October 8 a configuration repeats a September 8 design that was well observed around the world. Both the moon and Venus will again share the spotlight in the darkening evening sky. The moon revolves eastward around the Earth in a period of 27.3 days. While that is happening, the Earth continues trekking around the sun, causing the sun and Venus to move in an eastward direction among the background stars. When the moon finally completes its orbit around the Earth, it has a little catching up to do, not quite three days’ worth, in order for the configuration to repeat itself. This time, when the moon passes Venus on October 8, it will be positioned above the Goddess of Love because the moon’s track is tilted about eight degrees to the orbital path of Venus. The conjunction of Venus and the moon on the 8th will not be nearly as close as it was last month, but it will still be a very beautiful apparition. Be at your observing location with a good SW horizon about 30 minutes after sundown. The 18 percent lit, waxing crescent moon should be an easy target. Look underneath the moon and ever so slightly to its right to find starlike Venus. Binoculars will always make the viewing experience more enjoyable, but they will not be a necessary requirement for this super bright pair to be seen. Check the sky on October 7, and you’ll see Luna approaching Venus. On November 6, December 5, and January 2, about 30 minutes after sundown, the cycle repeats itself, but Venus and the moon will be slightly farther apart. Next week, a lunar eclipse comes to the East Coast.

895 OCTOBER 13, 2013: Ephemeral Lunar Eclipse: The East Coast is set for a different kind of lunar eclipse early on the evening of October 18. If you go outdoors around 7:50 p.m. EDT and look eastward at the full moon low in the sky, you may notice that the area around the five o’clock position on the lunar disk, may not look quite as bright as it should. Repeating the same observation an hour later should show that this same region has brightened considerably. What you will have observed is a penumbral lunar eclipse. Lunar eclipses can only happen when the moon is full, in other words, opposite to the location of the sun, and in the same direction as the Earth’s shadow. But as everyone knows, lunar eclipses do not occur every month, and that is because the moon’s orbit is tilted just over five degrees to the Earth’s orbital path. In order for a lunar eclipse to take place, the moon must be in its full phase, and its orbit must also be crossing the plane of the Earth’s orbit so that the moon can intersect the shadow of the Earth. The true shadow or umbra of the Earth at the moon’s distance is about 5700 miles in diameter, but surrounding it is a larger secondary shadow called the penumbra, a region where if you were on the moon looking back at the Earth, you would observe part of the Earth covering part of the sun. When the moon slips into this region, it does not receive a full blast of sunlight. The portion of the moon, deepest into the penumbra receives the least amount of illumination and takes on a dusky appearance. In this eclipse, no astronaut anywhere on the moon would observe the Earth completely covering the sun, so the primary shadow of Earth, the umbra, will never touch the moon’s surface. This will be an eclipse of comparisons. Observe the moon when it is deepest into the penumbra (7:51 p.m.), then observe it an hour later and compare. My guess is you will see this slight difference, an ephemeral lunar eclipse.

896 OCTOBER 20, 2013: Sunrise Solar Eclipse: Want some adventure? Go see the solar eclipse on November 3. Total solar eclipses occur when the moon passes across and blocks the light of the sun. Day turns into deep dusk, the planets and brightest stars become visible, and the moon is surrounded by the sun’s crown, the corona. Starting at sunrise, about 150 miles south of Bermuda as a ringed eclipse (the moon’s shadow doesn’t quite reach the Earth’s surface), the eclipse quickly becomes total and remains that way across the mid-Atlantic and cloud-draped equatorial Africa, crossing Gabon, the Congo, the Democratic Republic of the Congo (separate country), Uganda, Kenya, Ethiopia, and finally ending at sunset in Somalia. At the best site for favorable weather, near Lake Turkana in Kenya, the sun is eclipsed for a mere 18 seconds. It is one of the least travel friendly eclipses to have occurred in recent history, but there is a pot of “gold” at the beginning of the rainbow. The East Coast gets to see the sun rise on the morning of Sunday, November 3, partially eclipsed, and the eastern mid-Atlantic is the place to be to see maximum coverage. From Philadelphia, the sun rises with about 30 percent of its lower surface hidden by the moon. That’s not bad considering that a ringside view to see totality on a ship or on land in Africa will cost between 5-10 thousand dollars per person. The sun is a dangerous star to view, so you will need to acquire filtration to keep your eyes safe, especially as the sun gains altitude. My suggestion is to go to a welder’s supply shop and buy a #13 and a #14 welder’s filter. Both are safe for viewing the sun, but a #13 filter is best for the low altitude sun. If you have eclipse glasses used in a previous solar event, find them, because they will be your ticket for safe viewing also. The sun will rise in the ESE around 6:30 a.m. Check your local newspaper for specific times in your area. Much Success!

897 OCTOBER 27, 2013: Halloween: Death for most of us does not carry much appeal, until the very end of October when we celebrate Halloween, a sort of “nose thumbing” to our successful efforts in eluding the Grim Reaper for one more year. All Hallows’ Eve, October 31, has its roots steeped in astronomy, just like Groundhog Day, February 2, and May Day, May 1. They fall on what are called cross-quarter days, the midpoints between the four seasonal markers of the sun: the winter solstice (low sun), the vernal equinox (mid-sun), the summer solstice (high sun), and the autumnal equinox (mid-sun again). If you think about it, the cross-quarter day of October 31 is an apt time to celebrate avoiding death. The comfortable period of warmth and light is well beyond us. Our focus upon the encroaching darkness and cold of winter overwhelms our senses as the sun becomes lower in our noontime sky and rises later and sets earlier each day. Leave it to the Celts to have envisioned the harvest festival called Samhain (SAH-win), meaning summer’s end, the first and most important of the cross-quarter days, and then add a touch of the macabre. They believed that the veil which separated the living and the dead thinned on Samhain, permitting the creatures of the netherworld—souls of the dead, ghosts, fairies, and demons—to move freely about in our world. Sacrifices of animals and plants were made to the dead, and bonfires were lit to help guide the departed along their way and keep them separated from the living. Offerings of food and drink were left outdoors to pacify and keep these creatures from entering homes. Much later, people dressed in costumes and performed antics on others to receive a treat, leading to our more modern ritual of “trick or treating.” The reaction of the Church to these frolics was to add All Saints’ Day on November 1 and All Souls’ Day on the 2nd to conclude and Christianize the Halloween festivities.