StarWatch: Moravian College Astronomy

APRIL 2010

APRIL STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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Current Moon Phase

711 APRIL 4, 2010: Caught by Surprise: A few days ago while driving home, I was caught by surprise, when “on a lark,” I stopped at one of my favorite observing sites to note the location of Venus. In next week’s StarWatch you will learn about the close encounter that Mercury will make with the moon on Income Tax day, April 15. Venus will play an integral part in finding an extremely thin waxing crescent moon next to Mercury on that evening. I was interested in knowing whether this location would permit me the opportunity of witnessing the event. The setting is on a rise which overlooks a field and distant trees. It provides me with a near perfect western horizon that is only three blocks from my home. I turned onto N. Hillside Dr. and proceeded up the block and did my standard U-turn which pointed my car in the correct direction. There was Venus shining brightly above a silhouette of distant skeletal trees. “Wonderful,” I mused, as I imagined myself setting up my photographic gear and adjusting all of the knobs and buttons to take that one perfect digital image. But as I looked though my car window, feeling the elation of a near perfect moment beginning to sweep me away, I noticed a slow, pulsating light slightly below and to Venus’s right. “Darn,” I muttered to myself. “Another beautiful image marred by an airplane. There was just no justice.” But as I strained to detect any movement of the plane, there was none to be seen. It suddenly dawned upon me that I had just discovered Mercury. It had to have ranked as one of the clearest and brightest sightings of the Messenger God that I have ever made. After checking my computer programs when I got home, I discovered that this week offers an extraordinary opportunity to view, just to the right of Venus, the most elusive of the naked eye planets. Its brightness will be rapidly diminishing by week’s end, so act now if you also want to be caught by surprise like I was last week.

712 APRIL 11, 2010: Moon, Venus, and Mercury Embrace: In the hectic rush to finish your taxes on Thursday, take a short break to witness the conjunction of Venus, Mercury, and the moon right after sundown. I’ve often referred to the motion of the sun, moon, and planets as “the heavenly dance.” All of the steps are predicable, and it just takes a little patience for the players to occasionally do-si-do. That happens Thursday when an exceptionally thin, horned moon parks next to Mercury during evening twilight. Just seven degrees above the duo will be brilliant Venus. As always, you’ll want to scout for a location with an excellent WNW horizon because the action will be unfolding very near to the sky-Earth boundary. City dwellers living in high rise apartments with west-facing vistas are exceptionally well-positioned to witness this event. You should be at your observing location 30 minutes after sundown with a pair of binoculars, if possible. First, find Venus as the light of day begins to fade. It will be farthest from the sun and in a part of the sky that is just a little darker. View about two binocular fields above and to the left of the brightest region along the horizon. Venus will not prove difficult, and it may be already visible to the unaided eye depending upon sky transparency. About one binocular field below and to the right of Venus will be the main target. An ultra-thin crescent moon with only 2-1/2 percent of its surface illuminated by the sun will be just to the right and slightly above Mercury. Mercury, viewed through a high powered telescope, will also look like a thin crescent moon, and because of this geometry, Mercury will appear about as bright as one of the stars in the Big Dipper. That is faint because Mercury will still be enveloped in a heavy dose of evening twilight. Probably the best views will occur about an hour after sundown when the trio will be immersed in the deepening cobalt and oranges of a vernal sky.

713 APRIL 18, 2010: April Lyrids to Provide Spring Shower: The Lyrid meteor shower of April 22 marks the end of an unusually long drought of meteor activity which begins each year in early January. The dearth of shooting stars during the first quarter of the year may actually be good news for mid-latitude observers. Long nights coupled with cold, cloudy weather can have their challenges. The Lyrids might be better classified as more of a sprinkle than a shower. Meteor rates rarely exceed 10 events per hour. On the positive side, typical Lyrids are about as bright as the stars of the Big Dipper, allowing enthusiasts from more light-polluted locales to see them. Lyrid brightnesses may also indicate that the stream has been active for a long period. Smaller particles released from the dusty tail of a comet, in this case Comet Thatcher (C/1861 G1), can have their orbital paths modified by nongravitational forces. The directional heating of partials by the sun and then their cooling in different orientations (Poynting-Robertson effect) and the occasional jetting action of gases sputtering from the dust itself can modify the orbits of very small cometary dross. Even the pressure of sunlight has an effect. These same forces have almost no influence in changing the orbital paths of larger gains. If clear skies prevail, the morning of April 22, after 2 a.m., will be the ideal time to spot Lyrids. The waxing gibbous moon will be near its setting position and the radiant, the area of the sky from which the meteors will be diverging, will be above mid-sky in the east. That location is in the constellation of Lyra the Harp which also sports Vega, the fifth brightest star in the nighttime heavens. See the map showing the Lyrid radiant in the online version of this article. If a shooting star is seen and its path can be traced back to Vega, it will most likely be a Lyrid. Dress like it is winter. Face east and view overhead, normally the darkest part of the sky.

714 APRIL 25, 2010: Ernie's Telescope: I do not consider myself a person who is envious of the possessions of others. So when Priscilla Andrews, a good friend of mine, contacted me about selling her father’s telescope, I was honestly humbled. Eventually nine months later, I made the purchase. Priscilla’s dad, Ernie, who died in 1996, was the rector of Zion’s Reformed United Church of Christ in center city Allentown, PA; but it was not through professional affiliations that we became acquainted. It was purely through the joy of astronomy. Ernie was one of those singular individuals who had the ability of instantly making you like him. In a hobby that can be very competitive, he was sincere, considerate, unassuming, and passionate about the universe. He believed that the most lavishly constructed places of worship could not come close to emulating the beauties of the starry heavens under which he used to pray. Ernie was particularly zealous about Mars and humankind’s exploration of the Red Planet. The telescope which he purchased, a 4-inch Quantum Maksutov reflector, was specifically designed for lunar and planetary work, and it was portable enough so that he could still use it as the infirmities of age began to take their toll. His patience was unending. Ernie would spend hours looking at Mars, waiting for that transitory moment of perfectly calm air when intricate surface details would be revealed. In fact, friends told me that one Saturday he spent the entire night watching Mars though the eyepiece of a large refractor. Those same buddies took him to breakfast in the morning, and then to church where he presided over what they said was an electrifying service. In his honor, I pointed Ernie’s scope at Mars on the first evening of its use. It is a superb piece of optics, but more than that, it is a fond and gentle reminder of a passionate and compassionate soul that was kind enough to call me his friend. Ad astra!