StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

MAY 2014

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

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Current Solar X-rays:

Current Geomagnetic Field:

924 MAY 4, 2014: Planets Create Visual Treat: With the cold and rain that shrouded the East Coast last week, it felt as if winter’s bony grip was going to take us right into summer. May, however, is the transition period, where near the month’s end, warmer conditions will begin to take over, and going outside to view the stars will not involve all of the thought processes of “what to wear.” By June 1 the sun will be within two degrees of its summer solstice high, so it’s just got to get warmer. This week opens with a beautiful waxing crescent moon to the left of Jupiter in the western evening sky. As the days roll on, watch as the moon trudges eastward, towards another bright and reddish starlike object high in the east, reaching it by Saturday. That’s Mars, and it will be dominating the early summer sky. Mars will also be involved in several close encounters with the moon during the next few months. The best rendezvous will occur on July 5 when Mars and Luna will approach each other to within a half degree. By the end of this week as the moon is nearing Mars, another planet, Mercury, will be rising ever higher into the WNW after sundown. On Saturday, it will be about seven degrees above the horizon 45 minutes after sunset. In the WSW at the same time and at the same altitude will be twinkling Sirius the Dog Star. By the following week Sirius will be lost in the sun’s glare, but independent Mercury will have moved three degrees higher in the sky. Mercury continues to be well placed in the WNW right into early June, but it does become substantially fainter during this time. Binoculars will be a handy tool to help to make the finding of Mercury a little easier. This week, right after nightfall, look for a bright luminary in the southeast. That will be Saturn, visible for most of the night, another planet which will dominate the summer sky. That’s quite a treat, four planets, stretching across the heavens from west to east—Mercury, Jupiter, Mars, and Saturn.

925 MAY 11, 2014: Moravian Hounds Build a Comet: It’s hard to get students to read assignments, so when senior Anika Riaz came to me last month asking if we could make a comet, I asked her the origins of her wish. “Why from your book in the section on comets,” she retorted. I hadn’t even assigned that material, so how could I refuse her? On May 2 Anika and friends gathered in the commons area between PPHAC and Collier, and we did it. Comets were formed from the primordial leftovers of the solar system, far from the sun’s heat where ices, mainly water, but including carbon dioxide, ammonia, and methane, along with silicate grit, and even complex organic compounds existed. So the basic recipe wasn’t very complicated: 1/3 gallon of water, a dapple of ammonia, a fistful of sand, a handful of dirt for the organics, and about five pounds of pulverized dry ice (frozen carbon dioxide). The dry ice at -110o F. was the toughest commodity to acquire and maintain, so thank you, Dr. Carl Salter, for providing helpful suggestions and a storage container. A large bowl lined with insulating newspaper and layers of plastic from a garbage bag helped to form the general round shape of the comet. We added the water, ammonia, sand, and dirt and mixed the contents through the plastic bag. Another interesting aspect was pulverizing the pellets of dry ice. This was a task that the females of the group seemed to relish the most. In fact no guy volunteered. It just seemed to be too dangerous as mallets came smashing down on the towel covering the dry ice. Once the women were pulled away, the dry ice was slowly poured into the water, and quickly kneaded to mix all of the contents. Amid the hissing sounds and vapors spewing from the bowl, an icy, sputtering ball emerged. A little more water to form a crust, and voila, Comet Anika was born. Complete photo documentation can be found at www.astronomy.org. Click on the comet banner and enjoy the photos.

926 MAY 18, 2014: Meteor Watch, May 24: A high school demonstration that I performed to explain the effects of gas pressure on comets involved putting a dry ice pellet into a plastic film canister. Students were then told to attach the lids, and I continued to present until unexpectedly, there was a loud pop and a lid jetted six feet into the air. Within seconds a dozen or so canisters fired and there was “chaos in the classroom.” There was no bringing them back from that one except the passing bell to the next class. The point is that this is exactly what happens as a comet, which is like a dirty snowball, approaches the sun. Comets which have had repeated passages around Sol have picked up their share of dark surface grit which is a good absorber of sunlight. The sun bakes the comet’s surface causing the ices beneath it to change directly from a solid into a gas (sublimation), putting outward pressures on the crust which eventually cracks and ejects these gases and the dust into space. The ultraviolet light of the sun causes the gases to fluoresce (glow), while the dust tags along the comet’s orbital path creating its two distinctive (ion and dust) tails. If the dross crosses the Earth’s orbital plane at the Earth-sun distance as our planet moves through it, we get a meteor shower. That’s exactly what will be happening on the morning of May 24. Minor Comet 209P/LINEAR which recently had a small orbital change induced by Jupiter’s gravity has already passed the Earth, and we are scheduled to encounter its debris on the 24th between 1:40 and 5:50 a.m. EDT. Peak hourly rates are predicted between 20-140 events from a rural locale. The meteors are expected to be distinctively slow moving, bright, and radiating from near the North Star. So get your sleeping bag, air mattress, ground tarp, and “5 hour ENERGY” drinks ready. Face north, position your eyes a little above mid-sky, and prepare yourself for a “popping” good night.

927 MAY 25, 2014: Mercury for Memorial Day Weekend: Sunday evening, May 25, Mercury is at its greatest eastern elongation from the sun. Just what does that mean? Since we are viewing Mercury’s orbit nearly edge on, as the Messenger God revolves around the sun, it appears to shift from one side of the sun to the other side. Any elongation of a planet from the sun simply means the angular distance separating the planet from Sol. If Mercury is to the left of the sun, the Messenger God is visible in the WNW after sundown and is located to the sun’s east, even though it will be setting after sundown in the west, just as the sun did. When an inferior planet, a planet that is closer to the sun than the Earth, reaches its farthest distance to the sun’s east, it is termed the angle of greatest eastern elongation. That is what happens on Sunday to Mercury. This is a favorable elongation because in the spring the ecliptic, the Earth’s orbital plane, is inclined at a steep angle to the horizon in the evening sky, so elongations of Mercury will place the planet high above the sun and allow it to be seen well after sundown. In fact on May 25, Mercury sets one hour, 50 minutes after sunset, so if weather conditions permit, this is a premier opportunity to view the classical planet which is deemed the most difficult to see. Wait until about 45 minutes after sundown and bring along binoculars to help make Mercury more accessible against a brighter sky. Mercury will still be at an altitude of 10 degrees, but a good western horizon free from any obstructions is still necessary. This often makes high-rise apartments in urban locales with western exposures ideal for spotting Mercury, especially with a little optical aid. Don’t miss Jupiter 20 degrees to the left and above Mercury for added enjoyment. By Friday, May 30 a razor thin waxing crescent moon is to the left of Mercury, below Jupiter on the following evening, and to Jupiter’s left by Sunday, June 1. Good observing!