MAY STAR MAP |
MAY 2, 1999: Spring's Galaxies
- The winter sky is ablaze with bright stars because we are looking down one of the arms of our home galaxy, the Milky Way. When we look in the direction of Orion, we peer into a region of space ripe with clouds of hydrogen, the prime ingredient of the stellar birthing process. You can see the curtain call of winterís splendor low in the west, right after it gets dark. Now let your gaze drift towards the left and the hordes of brightly twinkling luminaries thin to just a few. Arcturus and blue-white Spica gleam as almost solitary sentinels in an otherwise bland sky. You can find them by following the arc of the handle of the Big Dipper southward. Arcturus is first, then Spica. Face north to see the Dipper almost overhead and upside down. Our view of the universe in spring is directed away from our galaxy which is basically pancaked in shape with a central bulge. You are never seeing very far into space when viewing the heavens in the plane of the Milky Way. Dust ejected from countless supernova events over eons of time has created a haze of pollution which even our most powerful optical telescopes fail to penetrate. The dust is most easily seen on clear summer evenings when the Milky Way arches across the sky. From rural locations darker rifts seem to bisect the soft glow of the Milky Way. This is the dust in the central plane of our galaxy. However, that bland sky of spring is a marvelous window into the deep reaches of space. Here in the region of Spica and lonely Arcturus can be found the countless galaxies which allow us to gain better insights about the vastness of the universe in which we live.
MAY 9, 1999: Venus by Day
- With winterís glorious stars setting earlier each evening and springís bland sky facing fully towards us, itís time to say a few words about those incredibly bright starlike objects flanking both the western and eastern skies in the very early evening hours. In the west gleams the planet Venus, while in the east youíll easily notice cream-colored Mars to the left of twinkling, blue-white Spica. Weíll focus on Venus this week. It is easy to imagine how the Greeks and Romans could have called her the goddess of beauty and love. She is absolutely gorgeous, shining at magnitude -4.1. In fact, Venus is so bright that she can be seen in broad daylight with the unaided eye, if you know exactly where to look and the sky is a vivid enough blue. If youíre interested in attempting a daylight sighting of Venus, find it first about 30-45 minutes after sundown, high in the west, and then go out earlier each succeeding clear evening to see it again. Chose an observing position which will be shaded from the sun while still affording a view of the sky where Venus can be seen. I have observed Venus in mid-afternoon, but I would start with early evening observations and hope to catch it a few minutes before sunset. Returning to the same observing spot is essential, because youíll have a mental image of Venusí location framed against a familiar terrestrial backdrop. Since observing Venus during the day is not a test of sky darkness, the city dweller has every reason to participate too. Give it a try. Youíll be surprised at how visually acute your eyes can be!
MAY 16, 1999: Moon to Occult Regulus
- A rare naked-eye occultation (eclipse) of the star Regulus by the moon will take place this Saturday morning low in the western sky just after midnight. Regulus is the brightest star in the constellation of Leo, the lion, and it is the 21st brightest star of the nighttime sky. The moon will be at first quarter on Saturday morning, making it appear as if it is only half illuminated. Since the moon will not be overwhelmingly bright, and Regulus will disappear in back of the unlit portion of the moon, the event should be seen by the unaided eye if sky conditions are very clear. The use of binoculars, and especially telescopes, will add immeasurably to your enjoyment, because you will be able to isolate the unlit portion of the moon and see Regulus more clearly. Through telescopes youíll notice that the dark part of the moon will be highlighted against an even darker sky. Thatís because some sunlight reflected from Earth is reflected back to us again from the moonís unlit hemisphere. Start observing around 11:45 p.m. Friday, so you can watch the event unfold. Regulus should appear just above and slightly to the left of the moon through binoculars. Telescopes will flip the image around, but identifying Regulus will be a snap. Watch as the moon slowly overtakes Regulus during the next half hour. As the star gets very near to the moonís limb (edge), be prepared for an abrupt disappearance. There will be no gradual fadeout because Regulus is essentially a pinpoint of light, and the moon possesses no atmosphere. Regulus will appear to simply vanish in an instant. The predicted time of Regulusí disappearance for Allentown is at 12:17 a.m. Saturday.
MAY 23, 1999: Mars Brightens Evening Sky
- With the clear and mild spring weather we have been experiencing, you should easily find Venus high in the west about one half hour after sundown. This bright gem doesnít set until 11:45 p.m., keeping Venus well-positioned and high enough in the sky for easy observations until about 10:30 p.m. You may have also noticed another bright starlike object in the south, southeast around the same time. This is the planet Mars. While Venus glows almost pure white, Mars is more cream-colored, and it is companioned with blue-white Spica, the brightest star in Virgo, the Virgin. If you compare Mars and Spica, youíll immediately notice that Mars shines with a steady light. Spica is twinkling ferociously, a dead giveaway of how you can usually tell a planet from a star. Mars has been grabbing the spotlight for quite a while. It was said to have been the abode of life one century ago when it was falsely believed to possess canals. Several years ago, samples of two meteorites discovered in Antarctica were thought to contain evidence of fossil bacteria. These meteorites were probably lobbed off the surface of Mars when other larger meteorites struck the Red Planet tens of millions of years ago. The frenzy has died down in favor of a nonbiological explanation. However, our two Viking Landers in 1976, Pathfinder in 1997, and now the Mars Global Explorer continue to whet our appetites about this planet which does have many Earth-like characteristics. Go to the web page listed below and click on the Mars button to find out the latest information (including photos) about our remote explorations of the Red Planet.
MAY 30, 1999: Sunspots Galore
- If asked what is the brightest star in the sky, most people will immediately answer Polaris, the North Star. Upon quick reflection the response quickly changes to the sun. Polaris is famous for its stationary position, not its brightness which ranks it 49th in the sky, if the sun is included. The sun is just like many of the other stars we can observe at night, just closer, and therefore, brighter. Changing hydrogen into helium at the prodigious rate of five million tons of mass loss per second, it is halfway through its 10 billion year life span. Most of us just nix the sun as an object which we can observe in detail. If stared at, even for a few seconds, its infrared radiation can cause permanent retinal burn. Concentrated sunlight easily ignites paper when held at the eyepiece of an unfiltered telescope or when focusing its light using a magnifying glass. However, with the proper filtration, the sun currently is yielding a wealth of detail in the form of sunspot activity. About every 11 years this activity culminates in a multitude of dark membrane-like splotches which sometimes gird the solar disk like soldiers on parade. Sunspot activity is on the rise right now, and the public is invited to take a peek next Sunday, June 6, at the 10th annual Rose Garden Childrenís Festival, 8th Ave. and W. Union Blvd., Bethlehem. Itís right across the street from Nitschmann Middle School. Members of the Lehigh Valley Amateur Astronomical Society, including your StarWatch author, will have their telescopes set up and focused on Sol between 12:30 p.m. and 5:30 p.m. Weíll also try daylight sightings of Venus if sky conditions are clear enough. Come join us for a look at the supreme star of the sky.