StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

NOVEMBER 2007

NOVEMBER STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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

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585 NOVEMBER 4, 2007: Comet Holmes Continues to Please: When Mark Balanda of Hershey, PA called to inform me about a comet that had suddenly brightened, I had to admit I was skeptical. Halloween was the following week, and the East Coast was shrouded in clouds. But then I went to SpaceWeather.com and saw images of 17P/Holmes that observers around the world were snapping. I was flabbergasted. When the weather cleared on October 27, I finally met Holmes for the first time in center city Bethlehem. It had been 10 years since my last encounter with an urban comet, and that was the grandest of them all, Hale-Bopp. I have been photographing Holmes on every clear night since, and you can see my shots by going to the URL below and clicking on “this week’s StarWatch.” What happened to dinky Holmes, to transform it into a fuzz ball visible to my Allen and Dieruff students in center city Allentown? It is thought that a sinkhole collapsed on the tiny one-to-two mile diameter nucleus which triggered an explosive amount of outgassing caused by the sun’s heat. The gasses pushed out huge quantities of dust which were sprayed like a turning garden hose as the nucleus rotated. The result has been a circular halo of debris now over one million miles in diameter, scattering sunlight back to us and creating the fluffy blob of light near the bright star Mirfak in Perseus the Hero. Why the media hasn’t picked up on this is anyone’s guess, but it is the top story if you’re an astronomer. Telescopes have been focused on Holmes since its October 24 eruption. Comet 17P/Holmes won’t be around forever. Its expanding coma will eventually get so huge that it will simply disappear against the sky background. Locally, we probably have this week to see it before it fades. We can always hope for another eruption which is a real possibility. Stay tuned!

586 NOVEMBER 11, 2007: Comet Holmes Down but Not Out!: The last two weeks have been really what astronomy is all about—witnessing the unexpected. Suddenly, on October 24, a faint, no nothing comet by the name of 17P/Holmes brightened by over 600,000 times to become visible to the unaided eye, the best northern hemispheric interloper since Hale-Bopp in 1997. Locally, the weather cleared on the 27, and there it was in the NE about two fists held at arm’s length above the bright star Capella at 9 p.m. During the next week the weather was mostly clear, and my nightly sojourns into my front yard with camera and telescopic mount yielded a bonanza of images detailing the expanding gas and dust shell surrounding Holmes. Against all odds, the comet grew even brighter, visible easily as a fuzzy ball below the bright star Mirfak in Perseus the Hero. See the online map and photos starting at the top of the November StarWatch articles by going to the URL below. Click on “this week’s StarWatch.” The dusty coma of Holmes has grown to over one million miles in diameter, and the comet has even sprouted a small tail seen when using sophisticated imaging systems. Because the material is thinning, the luminosity of Holmes has begun to wane. If another outburst does not occur, I suspect that its diminishing brightness will make it fade as a faint moon-sized fuzz ball against the suburban sky background sometime during this week. Rural areas with darker skies will see Holmes for a slightly longer period of time after moonset. While you’re Holmes spotting, you might catch a brilliant Taurid meteor. I saw one on November 3 which went across a fourth of the sky, wavered, and flashed near the end of its trial. The Leonid shooting stars also max on the morning of the 18th, with perhaps as many as 10 meteors per hour radiating from the Sickle of Leo the Lion. Good observing!

587 NOVEMBER 18, 2007: Comet Holmes: An Easy Target: It’s now official. The sun is no longer the largest object in our planetary system. On November 9, the expanding dust and gas cloud surrounding Comet Holmes surpassed our 864,000 mile in diameter daystar to become the most voluminous object in our solar system. The structure of Holmes was created from the ejection and interaction with the sun of several to a dozen cubic city blocks of ice laced with embedded dust. The event may have been triggered when a sinkhole collapsed on the one-to-two mile in diameter nucleus exposing fresh ices to the sun’s blistering heat. The outgassing which began on October 24, and was similar to the spray from a rotating garden hose, has now expanded the coma of the comet to about one million miles. Happily, Holmes did not fade as rapidly as I anticipated, although it has become invisible as a naked eye phenomenon from center city Allentown. It was still an easy catch with binoculars last week from the Dieruff H.S. campus in east Allentown. From suburban locales like Coopersburg, Holmes is still accessible with the unaided eye as I have continued to witness it on every clear night since its outburst on October 24. During this week 17P/Holmes will be a snap to find because of its proximity to the star, Mirfak, in Perseus the Hero. By 8 p.m. the brilliant star Capella will be low in the NE. Hold a clenched fist at arm’s length and place the bottom finger right above Capella. Move up one more clenched fist in distance, and your thumb will be just below Mirfak, the brightest luminary in Perseus. On Monday, Comet Holmes is in front of Mirfak. Use binoculars to enhance the brightness of Holmes. As we get deeper into the week, 17P/Holmes will move above Mirfak, but it will still be within a binocular field of view. Maps and photos are posted at the URL below.

588 NOVEMBER 25, 2007: Imagine the Infinite: Now that there is the crispness of autumn in the air, we have a valuable opportunity to gaze at the nighttime sky unfettered by the heat, haze, and humidity of summer. Arching overhead, the heavens go vastly unnoticed during muggy summer eves, but when it is seen for all of its glory during the cooler seasons, we are participating in an activity that links us to the ancients—stargazing. Cygnus the Swan, Lyra the Harp, Aquila the Eagle—the constellations of summer are waning rapidly in the west, setting earlier each evening, and the colorful and bright winter stars, such as Capella, Aldebaran, Betelgeuse, Rigel, Procyon, Castor, Pollux, and Sirius are arriving at their eastern gates. If we have the good fortune of possessing a clear and accessible horizon, they appear quietly, but abruptly, like a royal retinue attending kingly constellations that rise brilliantly against an indigo backdrop. What they and the night bring to us is a moment of quiet, a time to reflect upon our place in the cosmos, a wonderment in knowing that the universe holds the mysteries of our existence, and the existence of countless other beings too. Gazing skyward into the heavens, studded with diamond stars makes us pause to understand that the universe is infinitely larger than our problems and pettiness. The sky in some form or other is accessible to us all. It is a beacon for all peoples, nations, and cultures that can help bring us face-to-face with our humanity and humility. How do we comprehend the greatness? Can we exist in the far reaches of the dark? What hopeful messages can we glean from those stars that seem to ripple in the cosmic fabric and tantalize us with their secrets? Take out a thermos of coffee some clear autumn evening and let your mind flow freely to imagine the infinite that lies just above your head. Susan B. and Gary A. Becker

[November Star Map]

[November Moon Phase Calendar]