StarWatch: Moravian College Astronomy

DECEMBER 2017

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

Print Large Sky Charts For 9 p.m. EST: NORTH | EAST | SOUTH | WEST | ZENITH

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lunar phases

1111 DECEMBER 3, 2017: Geminids Coming to a Sky Over You: On the evening of December 13 and the morning of December 14, one of the great meteor showers of the year takes place. Under perfect conditions the Geminids can produce as many as 120 meteors per hour; however, those numbers are more than halved in the light-drenched suburban areas of the East Coast. Geminids move at a relatively slow pace, and some can be exceedingly bright, but cloudy weather and the chill of wintery temperatures have kept them from becoming as popular as the August Perseids. Meteors from an organized shower diverge from a small point in the sky called the radiant, and this position for the Geminids is located just a few degrees to the northwest of the bright star Castor, the mortal twin of the Gemini brothers. Their origin stems from the debris discarded by a periodic comet turned asteroid that is in orbit around the sun. The meteoroids, the small specks of dislodged cometary dust, are moving parallel to each other in an analogous fashion to a pair of railroad tracks along a straight section of track. The rails would appear to diverge from a distant vanishing point. In meteor astronomy the vanishing point is called the radiant. It is a relatively simple task for anyone who has the desire to view an organized shower of shooting stars to tell whether or not the meteor they have just witnessed belongs to that group. Its path will be traceable back to the radiant position. Because the moon is in a gibbous phase for most of this week, its light will only allow the brightest stars to be visible, and this will actually aid in finding the Geminid radiant point. Begin with Orion, the greatest hunter in mythology, at 10 p.m. in the SSE. Seven stars form his body, two for the shoulders, three for his narrow waist, and two luminaries for Orion’s knees. They are all bluish in appearance except for orangey-red, supergiant Betelgeuse, the shoulder star on the left side of the Hunter as we view him in the sky. Orion, in the Robert Frost poem, The Star-Splitter, “…always comes up sideways, throwing a leg up over our fence of mountains, and rising on his hands, he looks in on me…” You’ll see him that way in the 8 p.m. to 10 p.m. time slot of early December. From Betelgeuse, move cattycorner to Rigel, a blue supergiant, and most of the time the brightest star of the Hunter. Connecting Betelgeuse and Rigel, move leftward two of these lengths, and you will be above two bright, closely spaced, white stars which are the heads of the Gemini Twins. The star closest to your line segment is Castor, the region from which Geminid meteors will be radiating. Meteors will be plentiful coming from this locale, particularly after midnight on the morning of December 14; but for the moment, go outside and see if you can find the location of the radiant with bright moonlight illuminating the sky. A map to assist you is online at http://astronomy.org/StarWatch/November/index-11-17.html#11-26-17. Wishing everyone good radiant hunting.

1112 DECEMBER 10, 2017: It's Showtime for the Geminids: As Holiday lights continue to spring up over the Lehigh Valley, there is a celestial light show that is gaining strength in the nighttime sky. Geminid meteors are already flying this week, and their numbers will continue to climb throughout the evenings hours and mornings of December 13-14. If this shower occurred during the summer, it is safe to say that the Geminids, rather than the August Perseids, would be the biggest shooting star event of the year. They would outpace the Perseids by a margin of two to one. Meteor showers arise from the debris released by a comet as it orbits the sun, and this dross crossing near enough to Earth’s orbital path encounters our planet, penetrating the atmosphere to produce the meteor phenomenon, a tube of glowing air created by the dust particles moving up to 44.7 miles per second. Until recently, the Geminids had no comet progenitor. Then in 1983 an Apollo class asteroid, a minor planet which has its closest distance from the sun within Earth’s orbit, now known as 3200 Phaethon, was discovered with a similar path to the Geminids. Having an orbital period of only 524 days, Phaethon careens within 13 million miles of the sun at its nearest approach, a record for named asteroids. The discovery of Phaethon and its relationship to the Geminids gave credence for a proposed theory that some comets never die; they just fade away to become asteroids when their orbits are perturbed by the giant planets. In this case it was Jupiter. Meteor observing was responsible for my getting interested in astronomy. Not having enough money to buy a telescope and not really knowing what to purchase, it was just fun to lay out under the stars in a chaise lounge in the summer or nestle in a sleeping bag during the fall and late spring. Winter and the Geminids was a whole different story. The cold and the increased cloudiness are major reasons why the Geminids are not better known. During my most recent attempt in 2012 to observe them, I lasted just under four hours, even with being bundled up in several sleeping bags and numerous thermal clothing layers which just didn’t seem to ward off the cold. Several balaclavas and a half dozen hand warmers in various pockets probably kept me going for an additional hour. Watching meteors is not the same as other winter activities, such as skiing or snowboarding, where increased physical activity keeps you cozy while in the cold. You are lying motionless, and the chill just seems to seep in. My suggestion is to go outside for 10 to 15 minutes at a time, then get warm again for an hour or two. Geminid meteors will be visible as soon as it gets dark, but optimal conditions occur after midnight when the radiant, which lies very near to the bright star Castor in Gemini the Twins, gains some altitude. The shower is forecast to produce its maximum number of meteors at 1:30 a.m. EST on Thursday, December 14 which puts East Coast residents in a prime location for spotting Geminids. Bundle up, look up, and enjoy the Geminids. See last week’s StarWatch at http://astronomy.org/StarWatch/December/index-12-17.html for additional Geminid details.

1113 DECEMBER 17, 2017: A Telescope Under the Tree: It is still not too late to purchase that telescope for under the tree this Christmas, but there are some common mistakes that people often make when buying their first scope. All telescopes are compromises in one way or another, but all experts agree that telescopes are not built strictly for magnification. If manufacturers hype the power that a telescope can attain as the chief reason for purchasing their product, stay away from them as if they were the Grinch. The most important attribute of a telescope is its ability to gather light, a greater amount of light than the human eye can collect—more light to see deeper into space and to view fainter objects. In addition, a good telescope and eyepiece combination will bring the light collected by a mirror or a lens to a crisp, high-contrast focus, and in a manner which produces a comfortable view for the observer. The eye, acting as the receptor of the gathered light, essentially becomes as large as the surface of the light-gathering area of the telescope. A second consideration is the steadiness of the telescope’s mounting system. If it is flimsy and wobbles, all of that unwanted motion will be transferred to the telescope and magnified by the eyepiece making it difficult to point the scope and hold steady the object that is being viewed. Department store scopes like those sold at K-Mart or Wal-Mart are overpriced, poorly constructed, and of inferior optical quality. The idea is to be “turned on” by what you are viewing. If you are disappointed by the images which your scope is producing, it will never be used and wind up in the closet gathering dust. Inferior telescopes quickly drive potential enthusiasts to other hobby interests. Manufacturers like Orion, Celestron, Explore Scientific, and Meade produce good instrumentation in the $300 to $600 range, and all have websites hyping their products. My suggestion, if you’re thinking about a scope for Christmas, is to visit a retail store that exclusively sells telescopes and to talk to a knowledgeable individual who knows the market and can make appropriate suggestions. Places like these are few and far between, but locally serving the Greater Philadelphia, south Jersey, and Lehigh Valley regions is Skies Unlimited (skiesunlimited.com) in Pottstown, PA, at 52 Glocker Way, 19465 (888-947-2673). They normally have lots of used and new equipment on their showroom floor, real telescopes, and many at affordable prices. Skies Unlimited has been instrumental in helping me to upgrade and repair many of the donated telescopes that Moravian College has acquired during the past three years. Talk to Bob, Ted, or Dave for a no pressure introduction to the telescope market and feel free to mention my name. They will listen to your needs and make suggestions in a no pressure environment. I really think that is what makes Skies Unlimited extra special. Skies has treated Moravian College and me very fairly and will do the same for you. Happy Holidays and keep looking up!

1114

DECEMBER 24, 2017: Christmas and the Saturnalia

I am writing this StarWatch on the winter solstice, not because I wish to celebrate this season of the long shadows, but because it represents the end of a trend. The days have been growing shorter ever since the summer solstice which occurred just after midnight on June 21. This trend has now ended, and daytime is finally lengthening. The decrease in the amount of daylight is not anything we readily perceived until sometime in mid-August when the observance of earlier sunsets begins to accelerate rapidly, and summer temperatures ease just a little. As the equinox approaches on September 22, it still is not much of a concern because warmer conditions can persist even throughout October. That is called the lag of the seasons and results from Earth’s heat budget not staying in step with the solstices. In other words, at the summer solstice the Northern Hemisphere is still absorbing more energy than it is radiating back into space at night, and daytime highs are still on the increase throughout much of July until a balance is reached. Likewise, the Earth continues to cool for about five weeks after the winter solstice until the energy received during the day equals the energy released at night. This cooling trend accelerates rapidly around Halloween when the darker, colder days of November descend upon our collective consciousness, and it begins to feel as if winter is beckoning. The approach of the winter solstice or midwinter as the English describe it, represent the final invitation to the longer, colder days which loom ahead. Roman priests felt a similar sentiment as they watched for the first signs of a higher noontime sun or Sol rising just a little to the north of its southeastern limit after the winter solstice. That observation usually occurred around four or five days after the lowest noontime sun, and it signaled a time for a celebration to the god of the harvest, Saturn. Warmer conditions would return to the empire, crops could be planted, and a bountiful harvest certified. The Romans were great partiers, and this celebration associated with gift giving, called the Saturnalia, lasted over many days, in fact, sometimes as long as a week. It is easy to imagine how early Christians would have used this solstitial celebration and lapse in Roman authority to celebrate in secret the birth of their Messiah, and how over the centuries, the true date and even the season in which Christ was born would have been forgotten in lieu of observing Christmas near the time of the winter solstice. This tradition was well established by the time the Roman Emperor Constantine allowed the open worship of Christianity in AD 313. The first record of Christmas occurring on December 25 was first chronicled in AD 336 and officially accepted by the Church under Pope Julius I in AD 340. For those who celebrate, a blessed Christmas to all.

1115

DECEMBER 31, 2017: Moravian Donor Attains Immortality

On January 1, 1801 Giuseppe Piazzi (1746-1826), an Italian astronomer on the island of Sicily, was compiling a new star catalog. Piazzi noted the position of a luminary which on the next night was not present. However, a similar star was observed near to the original star’s location. Piazzi initially thought that he had discovered a new comet; in fact, it was a new planet. He named it Ceres for the Roman goddess who gave agriculture to humankind. Then another “planet,” Pallas, was discovered on March 28, 1802 and then another on September 1, 1804. A fourth “planet” came into telescopic view on March 29, 1807. It became obvious after Pallas that these objects were representative of a new classification of smaller solar system bodies called asteroids (little stars). By the early 1990’s there were thousands of them known and a few dozen that had orbits which crossed the Earth’s path and could create havoc if they impacted. Then on March 24, 1993, a startling discovery was made by Eugene and Carolyn Shoemaker and David Levy. Calculations showed that Comet Shoemaker-Levy 9 was fragmented and in orbit around Jupiter and would hit Jove between July 16-22, 1994. The enormity of the energy released by the 20 impacting fragments dwarfed all expectations made by professional astronomers and set into motion a concerted effort by experts to discover and map the orbital paths of as many asteroids as possible in the hopes of discovering all Earth-crossing members. Today, we know of over 16,000 of them. Most are negligibly small, about 7000 large enough to create localized damage including the loss of life. Eleven-hundred of them are larger than 0.6 mile and could create real problems if they struck the Earth. The heyday of asteroid discoveries by amateurs was in the late 90’s, and it was at this time (1997) that James Robinson Bruton, a former student of Kutztown University astronomy professor and Moravian donor, Dr. Carlson R. Chambliss, discovered two asteroids, one of which he named after Chambliss. Carlson was also my astronomy professor when I studied at Kutztown University (1968-72). Chambliss has underwritten about half of the funding for Moravian’s 25 percent usage time for the MDRS Robotic Observatory near Hanksville, Utah. Jim was also my student teacher at the Allentown School District Planetarium during the fall semester of 1983. His genuine interest in astronomy and his unique perspectives in teaching difficult concepts earned him an evaluation of outstanding. When Jim first observed 23707 Chambliss on October 4, 1997, he was working as a science teacher in Chinle, Arizona on a Navajo reservation. This non-spherical, main belt, silicate asteroid, 7.198 km at its greatest length (4.5 mi.) has an orbital period of 5.53 years. It rotates once every 5 hours, 4 minutes. More importantly, 23707 Chambliss has been modeled photometrically. We know its general shape, and if you would like to see it for yourself, go to https://space.frieger.com/asteroids/asteroids/23707-Chambliss. If you are into immortality, having an asteroid named for you is a wonderful way to be celebrated. Congrats, Dr. Carlson R. Chambliss, on this exceptional and deserved honor.

Unaware that an asteroid had been named after him, Carlson R. Chambliss was performing a Google search of himself when he came across the fact that former student, Jim Bruton, had discovered an asteroid in 1997 and named it for him. Only about 1000 of the more than a quarter-million asteroids which are known have been modeled, making asteroid 23707 Chambliss even more special. View a 3D model of 23707 Chambliss at https://space.frieger.com/asteroids/asteroids/23707-Chambliss.