StarWatch: Moravian College Astronomy

DECEMBER 2021

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

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Current Solar X-rays:

Current Geomagnetic Field:

lunar phases

1320 December 5, 2021: Orion: Winter’s Sign Post: The other morning while I was watching the near total lunar eclipse unfold, I was mindful of the greatest hunter, Orion, staring down at me. His one arm was raised high above his head, his hand firmly grasping a club ready to give Taurus the Bull a beatdown if he approached too closely. The other arm was holding a shield with the impenetrable skin of the Nemean Lion stretched across it to protect himself against the piercing horns of the charging beast. • December marks the beginning of Orion time, when the Hunter, as the American poet Robert Frost exclaimed in The Star-Splitter, “…Comes up sideways, throwing a leg up over our fence of mountains, and rising on his hands, he looks in on me…” In my backyard, the “fence” happens to be a stand of tall ash and maple trees placed along the borders of neighboring properties, but the feeling of “looking in on me” holds true as Frost had written it so many years ago. • Orion isn’t just a “pretty” star pattern; it contains some of the best astronomical objects that the heavens can muster. In fact, it is such a powerhouse of activity that my advisor and sponsor when I was a graduate assistant at West Chester University, Dr. George F. Reed wrote an entire book about it called The Astronomy of One Constellation. • The stars of Orion are positioned in a hydrogen-rich region of the Milky Way. All of the luminaries that outline his body and reveal his belt are young, less than 12 million years of age. Except for red Betelgeuse, their hearts beat vigorously producing a bluish hue on their exteriors, their internal thermonuclear engines pumping out massive quantities of energy, some more than 100,000 times the amount that our sun produces each second. They are called blue giants. • Take for example, the three belt stars of the Hunter, Mintaka, Alnilam, and Alnitak which make Orion’s pattern so distinguishable and which fit so neatly in the field of view of any pair of binoculars. See the Orion map below. Their luminosity is staggering when compared to the sun. Mintaka (upper right) generates enough energy across the entire electromagnetic spectrum to make it 191,000 times brighter than the sun’s luminosity; Alnilam (middle), 537,000 times; and Alnitak, 250,000 times more radiant than Sol. These three stars and many others are part of several OB associations. O and B stars are the hottest and most luminous first-generation stars to form in a star cluster. Their outpourings of mainly ultraviolet radiation push and compact the hydrogen gas surrounding them, leading to the creation of second generation, lower mass stars which complete most of the star formation in that particular cluster. Our sun was a second-generation star that was fashioned in some unnamed group that dissipated billions of years ago. The best known OB association in the Northern Hemisphere is the Orion Nebula found as the center starlike object below the belt in the sword of the Hunter. Binoculars reveal wings of expanding gas and dust and a bright spot near the center where some of the youngest stars of our galaxy have just been created. Estimates place this community called the Trapezium between 100,000 to 300,000 years of age. • Finally, two of the four brightest supergiant stars of the heavens also exist in Orion. Red Betelgeuse is nearing the end of its life and has consumed its supply of hydrogen within its core. It is more luminous than it has ever been with hydrogen now burning in a thin shell encompassing its core. Look for it to go supernova in the next million years. Catty-corner to Betelgeuse is blue supergiant Rigel, normally the brightest star of the Hunter. Definitely not a slacker, Rigel’s luminosity is about 120,000 times that of our sun. With the moon just past its new phase, this week’s sky offers the greatest constellation of the winter heavens in the southeast by 8 p.m. Orion is looking down on you tonight. Ad Astra!

1321

December 12, 2021: Bullish on Taurus

When I was in college, I was a member of a grazing occultation team sponsored by the US Naval Observatory. Our objective was to better pinpoint the location of the moon in preparation for the Apollo landings. We would observe the blinks and flashes of stars calculated to skim the limb of the moon, appearing and disappearing as they were occulted by mountains jutting outward from the moon’s boundary, and then reappearing again in the lunar valleys. I had set up my scope with permission on a farm in the Poconos for such an event. I was just getting ready to observe when the snorting and pawing of the ground by a bull caught my full attention. As I listened, I could hear the pace of his motion picking up until he was in a full charge, the thump-thump of his hoofs on the ground getting louder and louder as I stood motionless in the dark. I remember just cowering down, allowing my scope to protect me. Kind of comical when you think of it. Thank goodness, there was a fence about 30 yards away, but in the dark it could not be seen. The bull heeded the barrier, slowed, and came to a full stop, still pawing the turf, satisfied that he had scared the bejesus out of me. The actual grazing occultation was forever stripped from my memory banks because of that incident. • I am, however, reminded of that story every time I glance skyward to see Taurus the Bull rushing toward the Hunter, initiating the charge to protect the Seven Sisters (Pleiades) clinging to his back. • To find Taurus, follow Orion’s three belt stars upward into the heavens. You will encounter a near perfect “V” in the sky which is the star cluster called the Hyades, except for the brightest member, yellowish Aldebaran, which is positioned in its line of sight. See the map of this section of the sky below. Continue farther along and a small, gossamer nest of mistiness containing six to seven faint stars will be encountered, the Pleiades on Taurus’ back. • Both the Pleiades and the head of Taurus look splendid through binoculars. In fact, the gossamer nature of the Pleiades is a function of hundreds of unseen stars, plus several clouds of gas and dust through which the light of the Seven Sisters is being transmitted. On particularly clear, moonless evenings, binoculars will reveal a bluish haze surrounding some of the brighter Pleiades. • Both the Hyades and Pleiades are unique groupings of stars formed from large clouds of interstellar hydrogen and dust. Through binoculars the stars of the Hyades have a warmer hue, whereas the Pleiades look distinctly bluish, a sure indication that the Seven Sisters are younger and hotter. Blue stars have relatively short lives because they are “burning” their hydrogen at a much faster pace. Cooler stars shine with whitish or yellowish hues, indicating lower temperatures. In these clusters the blue stars are gone, evolved through their red giant phases and now sit as cooling white dwarf embers scattered among members of their group. Estimates place the Hyades at about 625 million years of age, and the Pleiades at about 100 million years. Examine the size of both through binoculars. The Pleiades cluster is smaller because it is about 430 light years distant while the bigger appearing Hyades are closer at approximately 150 light years. View them with just the eye or better yet, through binoculars to gain a brighter and more detailed sight. They can be found, mid-sky, in the southeast by 8 p.m. Ad Astra!

Map by Gary A. Becker using Software Bisques's The Sky...

1322 December 19, 2021: What Stars are These with Beams so Bright?: More lovely than the noonday light?
'Tis sent to announce a newborn King,
Glad tidings of our God to bring.
On the threshold of yet another Christmas, the heavens seem to be again adding their own rendering of Yuletide sparkle to the southwestern sky after sundown. This is not the gathering of two planets, similar to last year’s spectacular conjunction when Jupiter and Saturn were positioned only 1/10th degree apart on the winter solstice, but rather a string of four pearls, three of which are visible right now, and the fourth to make its debut most likely on Christmas Eve or Christmas. • Yes, two of the four worlds are the same performers that brightened last Christmas, Jupiter and Saturn. One year later, however, faster orbiting Jupiter has progressed well ahead of Saturn and now leads the ringed world in its eastward travels by just over 18 degrees. Jupiter’s brightness is still impressive, but both planets have faded somewhat since their greatest brilliancy in August because the Earth-to-planet distances have increased by nearly 200 million miles. Stunning Venus, the third planet currently visible, makes even Jupiter look a little dull. It is rapidly approaching inferior conjunction on January 8 when it will be positioned between the Earth and the sun, like the moon when it is new. Each day that passes brings the Goddess of Beauty closer to being in alignment with the sun and closer to the horizon, until just beyond New Year’s Day when Venus should disappear in the glare of Sol. • If you want to complete the Holiday roster by Christmas Eve or Christmas Day, a nearly perfect southwestern horizon, free from blocking trees and buildings will be required. You’ll have to be at your observing location 30 minutes after sundown by 5:10 p.m. for southeastern PA. I would also suggest bringing along a pair of binoculars because the sky will be relatively bright. With a little luck you will catch the fourth player, Mercury, lurking about three degrees above the horizon. • The good news is that Mercury will be gaining altitude each day, so if you miss it at Christmas, it will be easier to spot the following week. The best three days for seeing all four planets are December 30 through January 1, when Mercury will climb ahead of Venus. I would be at my observing site 35 minutes after sundown. Locally, that’s about 5:20 p.m. The lineup from closest to highest above the horizon will be Venus, Mercury, Saturn, and Jupiter. As always, binoculars will aid in the location of the planets, especially Saturn if sky conditions are still too bright for easy identification with the unaided eye. Maps for Christmas Day and New Year’s Day can be found below. • Don’t forget, the winter solstice is just around the corner too! The sun reaches its lowest noontime altitude, its greatest southerly rise and set positions, and the shortest time above the horizon on December 21 for the Northern Hemisphere. Happily, after the winter solstice, it is all uphill for the sun until summer begins early on the morning of June 21, 2022. Keep your eyes on the sky this Holiday Season! Ad Astra!

1323 December 26, 2021: Swansong for Comet Leonard: There was a comet in the sky, south of Venus the week before Christmas, and my wife Susan accompanied me to my favorite locale, high up on a hilltop, the only setting a few miles from home where I can still observe and photograph objects near to a true western horizon. I didn’t hype this comet because from this suburban area with all of its light pollution, Leonard never became a naked eye object nor was it even an easy target through binoculars. Unfortunately, many media outlets made it into a “big thing” with public disappointment as the resulting consequence. • Comet Leonard was discovered by Gregory J. Leonard at the Mount Lemmon Observatory in Arizona on January 3, 2021. I actually wasn’t following it until I saw Peter Detterline’s excellent December 5 image taken with the wide-field camera of the Mars Desert Research Station’s Robotic Observatory near Hanksville, Utah to which Moravian University has a 25 percent time-share in its usage. • Locally, December clouds were in full opacity for comet viewing until the 19th when we had excellent transparency on the western horizon, and it was now or never to try to capture the comet from the Lehigh Valley. I was particularly interested in netting an image of Leonard with Venus in the same frame, and to that extent, I was successful. Both Pete’s image and my photo can be seen below. Susan accompanied me on this photographic sojourn to capture Leonard and penned the following while I struggled to image it in the gusty cold. Here are her thoughts. • There’s a comet in the sky, south of Venus, opposite a huge, orange full moon that is climbing into the northeastern sky on this 32-degree December night. Venus shines steadily against a royal blue sky that is highlighted by a pale, yellow sunset. The yellow fades into a light powder blue, then to a deeper blue, then the rich blue that showcases the Goddess of Beauty. Bare trees stretch their limbs to the sky in praise of the Creator who has given us this blustery night. • Opposite the comet, the full moon now a serene yellow-white, is inching up higher into the sky. Its light is like a beacon, a guide for any without direction, a comfort for those who have wandered away from the familiar. Here in December, just one day from the beginning of winter, this landscape is a herald for the time of cold and snow. • “From a Distance” by Bette Midler is playing on Sirius radio because not all astronomical observers are out in the cold. I can also see the parade of planets, Jupiter, Saturn and Venus, in that order from the cozy warmth of Gary’s Jeep. Jupiter is highest and bright; Saturn looks like a tiny star, and Venus beams like a brilliant torch close to the horizon. It brings to mind other conjunctions like the one from last Christmas. Conjunctions are celestial lineups, a serene personification of the cosmic dance that accompanies all life. • The sunset is muted now, just a sliver of red-orange on the horizon. In a few minutes it fades to a smoky blue that blends into the darker blue of the fabric of the night. Gary reappears from the dark with his promising cometary portrait of Leonard, and “It’s a wrap” for the night. Ad Astra!