StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

AUGUST 2009

AUGUST STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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

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676 AUGUST 2, 2009: Cooling Sun: Maybe you haven’t noticed, but the sun is currently radiating 1/10th of one percent less energy. The slacking of the sun’s output has been ongoing for 17 months, resulting in the longest period of quiescence in nearly a century. The sun is a magnetic dynamo with sunspot numbers acting as the benchmark of activity. The sunspot cycle runs in periods of approximately 11 years, with about four years to build to a maximum number of spots and about seven years to decrease to minimum activity. Because sunspots are cooler, magnetically enhanced regions within the sun’s light-producing photosphere, it would seem natural to surmise that when the sun reaches its maximum number of spots, it should be coolest. But in reality, it is just the opposite. When the sun is pockmarked with spots, brighter, hotter locales around the sunspots form. These are called faculae. Faculae overcompensate for the diminution of energy resulting from the spots themselves. Therefore, a heavily spotted sun is a slightly warmer sun. Conversely, when the sun is devoid of spots, it becomes a little cooler. Originally, sunspot numbers were to have bottomed in March of 2008, but then old Sol went on strike, producing the longest period of inactivity since the solar minimum of 1913. What does this mean for us? The next several winters could be cooler and snowier than normal, giving global warming a reprieve for several years or even longer. Revised estimates of sunspot numbers at the next maximum in 2013 are also down, translating into a cooler, maximum sun. If activity drops to nearly zero like it did between 1645 and 1715, global warming could be brought to its knees. The winters of two to three centuries ago, like in Dickens’s The Christmas Carol (1843) or George Washington’s crossing of the Delaware (1776), were indeed much colder.

677 AUGUST 9, 2009: Perseids Will Please: On the morning of Wednesday, August 12 the Perseid Meteor Shower peaks, giving observers even from suburban locales, a first class opportunity to view the most famous and one of the best meteor events of the year. Under clear skies the Perseids rarely disappoint, producing dozens of fiery steaks across the heavens each hour as dust from the tail of comet 109P/Swift-Tuttle collides with the Earth to ionize and light up the atmosphere. This year, there will be a waning gibbous moon in the sky by midnight, stealing some of the Perseid thunder, but certainly not all of the show. By midnight the star pattern of Perseus will have risen fully in the NE along with the moon in the ENE. Above Perseus will be the sideways and rising “W” of Queen Cassiopeia. Perseids are fast movers, coming and going in as little as 1/10th of a second. They will appear to diverge from the top of the constellation of Perseus the Hero, a dead give away that a Perseid event has been seen. Face towards the north and observe the sky directly overhead where it is at its darkest. You’ll see more shooting stars if you keep the bright orb of the moon away from your field of view. Perseid meteors will appear to be fanning outward from just below the “W” around midnight. As the hours pass and Perseus climbs higher into the sky, the point from which the meteors are diverging, will also get higher and become more apparent. Dress for a chilly fall evening. A sleeping bag, an air mattress or lounge chair, a flashlight covered with red cellophane are essential. A plastic tarp to wrap around your bag and air mattress to keep the dew out will add comfort to the experience. Also, invite some friends. Observing in a group always proves to be more entertaining than observing alone. See the online map showing the Perseid radiant at the URL associated with this article. Enjoy the show!

678 AUGUST 16, 2009: Cruising Among the Stars: I get questions from time to time about watching the stars from cruise ships as they sail among ports. It’s a great idea if you plan just a little in advance. Ships often have an area, usually near the stern and on a mid level open deck, that is designated for sky watching and which is a little darker than other areas of the liner. In any of these locations stairwells will always be illuminated as well as anything else that poses a safety issue. The liability of not having a sufficient amount of light when happy hour is being promoted 24/7 precludes any location from being truly dark. On the “star deck,” you’ll be pleasantly surprised, however. It will not be populated by revelers. There will be an air of solemnity with people reclining in chairs, some with binoculars, some with simple star maps, but all looking up in hushed wonder. When in doubt, go to the purser’s office where most questions can be answered in a jiffy. One thing is certain; you must bring along binoculars. Beg, borrow, or steal them if you must, but don’t expect to secure one from the bridge as was done by a passenger on the Titanic. Binoculars are without a doubt the single most important piece of optics that you can bring along on any land, sea, air, rural, or urban vacation. They gulp in light while at the same time presenting a modestly magnified, wide-angle view, the best combination for showing the heavens in their entire splendor. When using binoculars, try to block extraneous light from getting into your eyes. You can wrap a small towel around your face or view through a small box lowered against the face. Lying on a deck chair will decrease neck fatigue, and you can always wrap yourself in a blanket if you get cold or the wind becomes a problem. You may look a little odd, but hey, there are a lot of weird-looking and odd-acting people on cruises. Join the fun in your own way!

679 AUGUST 23, 2009: Two Worlds Related: My wife, Susan, and I recently attended several special events at the Franklin Institute in Philadelphia. They were worlds apart and yet completely related—Star Trek, and Galileo, the Medici and the Age of Astronomy. Susan is a Trekker without the props and without a great desire to go to any of the conventions. She loves the original 1960’s series with Kirk blazing his way across the galaxy, but gives a much cooler reception to the spin-offs which followed. I am just the opposite, favoring the more elaborate sets of New Generation, Deep Space-9, and Voyager. The scores of people clandestinely taking cell phone images of costumes and props when museum guards turned their backs, made me think about how the much-touted tricorders of the 23rd century became the I-Pods of the early 21st century. I wondered what these devices would have looked like without the Star Trek blueprint. The Galileo exhibit was a world-class event, featuring the scientific equipment and manuscripts of Medici Florence and Europe, in general. It boasted original copies of Galileo’s books, exquisite watercolors which he made of the moon, and one of the two remaining refractors constructed, owned, and used by Galileo to make astronomical observations. For me it was the telescope that stole the show. Sitting in a large, climate-controlled, Plexiglas case, the refractor was positioned in a skyward angle that allowed me to imagine the great master himself peering through the eyepiece. Here, in a four-foot long, grey, paper-wrapped tube held together with neatly tied copper wire and glue, was the most important scientific instrument ever created for unveiling the mysteries of the cosmos. Without the telescope’s ability to discern the intimate motions of celestial bodies, it would have been impossible for us “to boldly go” into space.

680 AUGUST 30, 2009: Bright Star in the East: “We saw His star in the east and have come to worship Him.” Cut...! This is not a prequel to the Christmas story, but there is a bright star in the southeast as darkness descends, and it was worshiped for centuries by the Greeks, Romans, and other cultures as the king of all of the gods. It is the planet Jupiter, and it is beautiful to behold. Jupiter’s sojourn among the stars placed it in the late evening and morning heavens during much of the spring and summer. Only recently has it become visible shortly after dusk. That’s because earlier in the year, the sun-Earth-Jupiter geometry saw Earth catching up to Jove. Earth had to spin farther into the night to bring Jupiter above the horizon. On August 14, Earth and Jupiter were opposite to each other, and Jove rose at sundown. Now that the Earth has passed Jupiter, it is rising before sunset, making it visible very low in the ESE during dusk. By 10:00 p.m. Jupiter has climbed to nearly 30 degrees in altitude in the SE, still low if buildings and trees are present. Unfortunately, Jove won’t get much higher when it transits in the south just before midnight. That’s because it is in the part of the sky where the low winter sun resides each year. By late 2012 and again in early 2014, Jupiter will be shining down upon us from an altitude of 70 degrees in the winter sky. Jupiter received some notoriety in mid-July when amateur astronomers discovered an expanding black splotch in its southern hemisphere. The consensus by professionals was that Jupiter got whacked by a small asteroid in a similar fashion, but not as spectacularly as it did in July of 1994, when 20 pieces of fragmented Comet P/Shoemaker-Levy 9 slammed into its atmosphere. This, in comparison, was a hiccup, but proof that Jupiter’s gravity still continues to gobble up debris that could potentially harm the Earth and its inhabitants.

[August Star Map]

[August Moon Phase Calendar]