StarWatch: Moravian College Astronomy

SEPTEMBER 2016

SEPTEMBER 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:

lunar phases

1046 SEPTEMBER 4, 2016: Walking the Line: It’s being touted as the Great American Eclipse, and although it’s not a great eclipse with a duration of solar totality exceeding five minutes, its path traverses the entire continental US from the cool Pacific shores of Oregon to the sultry beaches of Charleston, South Carolina. On eclipse day millions of Americans will be in the path of totality, and tens of millions more will be traveling to the centerline where the moon’s shadow will be passing. Pete Detterline, director of the Boyertown Area School District Planetarium, and I spent five days this past summer following the centerline from mid-Nebraska through central Idaho in the hope of finding appropriate locations. We agreed that our most important priority was to view the eclipse and that the weather was far too iffy to pick a location east of the Mississippi; so we are counting on mobility, our capabilities to forecast the weather at least 24 hours in advance, and at least one night where my Jeep Sahara may also serve as our motel. Minus the weather, the biggest concerns confronting western eclipse chasers will be the remoteness of the event and the fact that the infrastructure simply will not be able to handle the influx of eclipse enthusiasts. Wyoming’s population is expected to double on E-day with Casper being the focal point. As many as 150,000 people from the greater Denver area may be driving northward on I-25 on Monday, August 21, 2017. The interstate will be gridlocked, and cars will simply run out of gas. We are packing extra fuel and water in our vehicle, as well as a cabaña for shade. Shoshoni, Wyoming, west of Casper, near the centerline has one gas station. Glendo State Park, east of Casper and on the centerline, is expecting 50 times its normal daily volume of visitors. Pete asked me where I thought we would see the eclipse. My answer to him is in a cemetery in western Nebraska or more likely along a flat stretch of desolate highway in central Idaho. Regardless of our location, just getting to this eclipse will be an adventure.

1047 SEPTEMBER 11, 2016: Wedding Crasher: It was the Perseid meteor shower that made me do it, crash a wedding in NW Montana this past August. It was just too good a “thing” to let pass—a beautiful lodge by Flathead Lake, incredibly dark skies, a cooperating moon, and a meteor shower that was predicted to be much stronger than average because Jupiter’s gravity had perturbed several strands of dross from previous passages of its parent comet, P109/Swift-Tuttle, into Earth’s path. Pete, my friend with whom I was traveling, also happened to be best man, and I did know the groom as a teenager. So maybe it wasn’t a crash as much as an awkward landing, but it was fun. Pete said that he had never seen anyone “crash” a wedding so gracefully. I’ll take that as a compliment. My hosts were also gracious. I got plenty of free meals, plenty of free drinks, and saw plenty of fine Perseids on two nights of consecutive observing. Montana weather can be a little tricky. While dry and partly cloudy to mostly clear on the majority of summer evenings, it can also be responsible for three to four consecutive days of cloudy, rainy weather, and that’s what we thought we were going to experience over the best Perseid mornings of August 12 and 13. However, it cleared just after midnight on the 12th and did those Perseids fly! They were brighter during the first several hours of watching with uncorrected visual rates of 30 to 45 meteors per hour. The most impressive part of the shower was the way the Perseids bunched. This may be due to a single larger particle breaking up and its daughter particles separating very slowly over the intervening centuries. The result creates bursts of meteors occurring within a 10 to 30 second interval. We witnessed several bunching episodes where five meteors singed the air in a 30 second period, and one where I saw six Perseids in about 15 seconds. WOW, the adrenaline was really pumping! I saw 184 meteors on the first night and 99 on the second (August 13), my best two consecutive nights that I have ever experienced.

1048 SEPTEMBER 18, 2016: Proxima: To “B” or Not To Be?: When the Robinson family (1965) in Lost in Space blasted from Earth on the Jupiter 2, a futuristic saucer-shaped spaceship, little did they know that one day “art” might actually imitate science. The mission was to take a single family on a five-and-a-half-year journey to a planet orbiting the nearest star system, Alpha Centauri. In 1965 it was known that Alpha Centauri had a companion star, a low mass, hydrogen burning, red dwarf called Proxima, circling Alpha. What the scientific community didn’t realize was that Proxima actually did have a planet orbiting it, and not in just any arbitrary location. “B” was in the Goldilocks Zone. You remember the fairy tale of The Three Bears and Goldilocks coming across their bowls of porridge while Papa, Mama, and Baby Bear were out for a walk in the woods? Goldilocks couldn’t resist entering the bears’ home and tasting the gruel, finding that one bowl was too hot, the other too cold, but the baby bear’s porridge was just right, just at the perfect temperature for eating. That is where Proxima Centauri B is positioned with respect to its orbital distance around Proxima, in the zone of habitability. In our solar system, Earth and Mars lie in the Goldilocks Zone. Proxima is positioned on the sunward side of Alpha, so it is the closest star to our solar system. Proxima B, therefore, is the closest exoplanet to us. It has a mass between 1.3 and 3 Earths and a temperature of -38 degrees F, if it does not possess an atmosphere. Take away Earth’s atmosphere, and our (equilibrium) temperature would be -1 degree F. Because red dwarfs are cool stars, Proxima B is only 5 million miles from its “sun” and completes one orbit in just over 11 days. Proxima is also known as a flare star prone to large changes in energy production which would irradiate the planet if it did not have a protective atmosphere. There are lots of other “ifs” with Proxima B surrounding its possibilities for supporting life. But who knows, maybe the Robinson family got it right after all?

1049 SEPTEMBER 25, 2016: The Planetary Diet: When Isaac Newton quantified gravity during the plague years of 1665-66, he laid the mathematical foundation for Apollo astronauts going to the moon three centuries later. What he discovered was the force of attraction between two objects was directly related to their masses, how much material they contained, and inversely proportional to the square of their distances (1/d²). Newton’s revolutionary concepts allowed us to calculate the true orbits of the planets and comets, the trajectory which took Apollo to the moon, and also the amount of matter which a system contained. In an even more simplistic form of Universal Gravity, the weight of a person standing on any planet or satellite could be known if you knew the weight of that person on Earth, and the ratios of Earth’s radius and mass to that of the object upon which the individual was standing. Take for instance our moon. Its mass is approximately 1/80th that of the Earth’s mass and its radius (center to surface distance) is just a little more than 1/4 of Earth’s radius. 1/80 divided by 1/4 x 1/4 = 1/80 divided by 1/16 which yields an answer of 16/80 or 1/5th of the gravitational attraction that the Earth possesses. The correct answer, if the exact numbers are incorporated, is 1/6th Earth’s pull. The Apollo astronauts when fully suited weighed on average 360 pounds, but on the moon they only weighed 60 pounds because the force of attraction at the moon’s surface was much less, 1/6th of Earth’s gravity or 1/6th of 360 pounds or 60 pounds. No wonder they were able to take giant strides as they walked across the lunar surface and jump two to three feet into the “air” when saluting the American flag. A 200 pound terrestrial moving to Mercury or Mars would weigh an anorexic 78 and 76 pounds respectively, but still look the same if housed in an Earthlike environment. Traveling to Jupiter would be an entirely different story, however, for that same person would weigh in at 500 pounds if there was a Jovian surface on which to stand. That’s the planetary diet.