StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

AUGUST 2016

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

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1042 AUGUST 7, 2016: Perseids on Fire this Year: Eclpses, comets, and the gathering of planets come and go in rhythmic patterns, but year after year, certain events reoccur with the confidence of a time-honored tradition. The Perseid meteor shower of August is one of these anticipated annual happenings, and it takes place during vacation season making this occasion even more appealing. Highest numbers are predicted for Friday morning, August 12, and this time around, rates could be elevated. Every 11.86 years Jupiter passes about 160 million miles beneath the stream of particles released by Comet 109P/Swift-Tuttle (Perseid progenitor), giving them a little nudge towards a better chance of rendezvousing with Earth. Enhanced rates were recorded in 1921, ‘45, ‘68, ‘80, ‘92, and 2004. Will 2016 also be enhanced? Activity from rural locales could top 100 meteors per hour, quarter that number from suburbia. Watching a major meteor shower is like witnessing John Denver’s Perseid description of “fire in the sky.” Unexpected outbursts, sometimes with 3-5 meteors flying in a minute’s time with an occasional brilliant fireball, can occur. The excitement can keep your adrenalin pumping for hours. An evening with the Perseids is time well spent; but don’t forget to dress warmly or at least have extra clothing on hand. I’ve always found it comfortable to nestle within the confines of a light sleeping bag on an air mattress with plastic ground tarps under and over my gear to protect it from the dew. You’ll find a pillow handy and also a thermos containing a warm, caffeinated beverage. Start looking around moonset, 12:30 a.m., August 12. Face towards the northeast but view overhead, usually the darkest part of the heavens. Shooting stars will appear to fan away from the border between Perseus and Cassiopeia. Many Perseids leave residual wakes and trains of glowing air after the initial meteor phenomenon subsides. My record for one night of Perseid viewing (1969) from dusk to dawn was 217 meteors. Much success!

1043 AUGUST 14, 2016: Mass: A Weighty Concept: “So you want to become rich?” I query my class in this thought experiment. I have become so famous as an astronomy celebrity (I’m fascinated by Neil de Grasse Tyson) that Madame Tussauds in NYC wants to make two wax “dummies” of ME and showcase them in an upcoming exhibit that will be featured in space. One dummy will be constructed in a normal fashion while the other one will be a wax coating of me under solid gold. Both will look exactly like me and be encased in a genuine NASA spacesuit. You, as the 50 millionth visitor to a Madame Tussauds museum, will be trained and flown to the International Space Station, and learn how to spacewalk so that you can choose a “Gary A. Becker” to take home with you. Obviously, you want the gold GAB and so do your 237,000 new Facebook friends. The moment has finally arrived. You’re outside the ISS in your spacesuit, and the two GABs are side-by-side in tandem with the ISS. What experiment will you perform to insure that the gold GAB, worth 3.5 million dollars, is chosen? There’s silence in my classroom. Thirty seconds—a minute flashes by… A hand slowly rises amidst a sea of students with downward looking stares. I recognize her. “Push them equally,” she says. “The gold dummy will move away more slowly than the wax dummy.” That is exactly the experiment I would perform too. On Earth the gold dummy would weigh more than the wax dummy because gold is denser than wax and has a greater force exerted upon it by the Earth due to its gravity. Gold has more matter (mass) per unit volume than wax, but up in space the concept of weight is meaningless. Just put a scale under each of the dummies and they better read zero. Since the gold GAB has more mass, it also has more inertia, resistance to change. Equal forces applied to each dummy will produce less change of motion to the gold Gary A. Becker. “That’s got to be worth a free point,” I exclaim. Another happy student… Now, on to general relativity…

1044 AUGUST 21, 2016: Venus and Jupiter in Close Encounter: When I was in my late teens and in college, I remember observing meteors on an especially dark night. My friend, Mark Adams, who became a professional astronomer, was intrigued with splitting Epsilon Lyrae, a double star with just his unaided eye. Their separation was 3 minutes, 29 seconds (209 seconds) of arc, difficult but not impossible. There are 360 degrees in a circle. Each degree can be broken apart into 60 minutes of arc, and each minute divided into 60 seconds, creating 1.296 million seconds of arc in a circle. Lyra the Harp was close to the zenith when we started observing, and within a few minutes, Mark spilt them. With less acute vision and glasses, I struggled. Every hour or so, I’d return to Epsilon to retry the experiment. Somewhere around 3 a.m., I either did it or hallucinated. I repeated the observation several more times to my enjoyment, but never again was I able to split those two stars. My best guess now is that the time of night was simply taking a toll on my rational brain. On Saturday, August 27, just after sundown this experiment can be repeated, with the third and fourth brightest objects in the sky, Venus and Jupiter. They will be just a little farther apart, under 6 minutes of arc in separation 30 minutes after sunset. Unfortunately, they will be only 4.5 degrees above the western horizon by that time, and binoculars will probably be necessary to separate them. If you want to try it, I’d start scanning the west about 15 minutes after sundown. My best guess is that Venus and Jupiter will be easy to spot with binoculars, but not yet visible to the unaided eye. Practice all this week as the two planets march closer together. On Sunday, August 21, Venus (brighter) and Jupiter are 6 degrees apart and a little higher in the sky 30 minutes after sunset. Mercury is below and to the left. By Thursday this distance has narrowed to 2 degrees, and less than 1 degree by Friday. On Saturday when they are closest, all of Jove’s four bright moons will be visible on the Venus side of Jupiter. Much success!
Footnote: On August 27, I easily split Venus and Jupiter with binoculars nine minutes after sundown, 7:50 p.m., but I was unable to divide the two visually with my unaided eye. The pair was followed to my local tree line, about two degrees above the western horizon and disappeared at 8:23 p.m. still distinctly separated through binoculars.

1045 AUGUST 28, 2016: Anticipating the Big One: Scores of Internet sites will be carrying this event live, but if you choose to participate online, you will be missing one of nature’s most spectacular happenings, a total solar eclipse. Most people who have witnessed darkness descend during midday and the wispy corona surrounding the moon want to see another. Some who are bitten by the “bug” chase them all over the world. I’ve witnessed five total solar eclipses, and I hope to be in Wyoming with friends on August 21, 2017 for my sixth. All of North America gets to see some partial aspect of this event, but along a narrow path about 65 miles wide, stretching from Oregon, through Idaho, Wyoming, Nebraska, Missouri, Illinois, Kentucky, Tennessee, Georgia, and South Carolina, the eclipse is total; in other words, the sun will be completely covered by the moon. During the partial eclipse, when part of the sun is still visible, special filters must be used to view the sun safely, but throughout totality, conditions are safe for direct observations because no part of the sun is exposed. As more of the sun is covered, the landscape grays into purplish hues, and shadows have less contrast. Several minutes before totality, the brighter planets become visible against what looks like an ominously dark cloud rising up from the horizon, the approaching shadow cone of the moon. However, it’s the last 10 seconds prior to totality that are often the most spectacular. The sun looks like a diamond ring decreasing in carat weight, until Sol is just shining through the valleys along the Moon’s limb—Baily’s beads. The viewer is absorbed in a shroud of darkness, the diminution of light so rapid that the eye cannot keep pace. Often the initial moments of totality appear to be the darkest. The intensity of light varies from three to six full moons depending upon prevailing haze and humidity. Bright stars may become visible, and the horizon has a peach-colored luminescence. If you have ever wanted to be wowed by nature, a total solar eclipse is one of your best bets.

[August Star Map]

[August Moon Phase Calendar]