MAY  2012

MAY STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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820    MAY 6, 2012:   Safe Solar Observing

Two events involving the sun are forthcoming within the next month. On May 20, a ringed solar eclipse tracks across the western US from Crescent City, CA to Sundown, TX during the early evening hours to sunset. See last week’s StarWatch at http://www.astronomy.org/StarWatch/April/index-4-12.html#4-29-12 to get the full details. The second event happens on June 5 and involves a transit of Venus across the solar disk, the last opportunity to see such an event until December 11, 2117. The Venus transit will be the topic of next week’s StarWatch. The task at hand when observing the sun is to diminish to safe levels the ultraviolet light, and particularly, the infrared radiation (heat) coming from the sun. To this effect, NEVER, NEVER, NEVER use sunglasses, multiple pairs of sunglasses, UV absorbing sunglasses, colored cellophane, colored filters, neutral density filters from photo stores, polarizing filters, fully exposed color negatives or fully exposed black and white photographic negatives (not containing a silver base), or glass smoked by the soot of a candle flame to make filtered, direct observations of the sun. All of the above methods can cause retinal burns and vision loss. So what is a solar enthusiast suppose to use? You can purchase a #14 welder’s glass or use any combination of welder’s glass that adds up to 14. To combat the green image that will result, purchase a gold-coated #14 welder’s glass for a few dollars more. Check for welding supplies online. Another consideration would be to purchase eclipse/transit glasses from a company like Rainbow Symphony— http://www.rainbowsymphonystore.com/gensolecshad.html. They are constructed from black Mylar, offer full protection for both eyes, a natural yellow view of the sun, and are under one dollar per unit. If you order this week, you’ll have the glasses by e-day for sure. Safe solar observing!

821    MAY 13, 2012:   Rare Venus Transit, June 5

On Tuesday, June 5, North America is posed for the rarest of astronomical events, a transit of Venus. Transits occur when a much smaller body passes in front of a much larger body. In order for a transit to occur, Venus must be crossing the plane of the Earth’s orbit at the exact time it is between the Earth and the sun. Because Venus makes almost exactly 13 circuits around the sun during the time that Earth makes eight revolutions, transits of Venus occur in pairs separated by eight years. The time interval between two pairs of transits is what makes this such an extraordinary phenomenon. Those intervals are 121.5 years and 105.5 years. The last pair took place in Decembers 1874 and 1882, while the next pair debuts in December 2117 and December 2125. The 243 year interval between 1882 and 2125 also reflect a periodicity relationship between the orbital intervals of the Earth and Venus equal to 243:395. With the proper filtration to dim the sun (See last week’s StarWatch article), Venus will appear as an easily seen black dot slowly moving in front of old Sol. Venus makes first contact with the sun at 6:10 p.m., EDT, June 5. For the next 18 minutes, Venus’ disk moves to a point of inner tangency with the sun (Contact II) at 6:28 p.m. For the next six hours and four minutes, Venus “sails” slowly across the speckled solar disk passing closest to the sun’s center at 9:30 p.m. At 12:32 a.m. June 6, Venus reaches inner tangency for the second time (Contact III) and slides off the solar disk 18 minutes later at 12:50 a.m. (Contact IV). Most of North America, except for the eastern third of the country, sees the transit past the point where it is closest to the sun’s center. Only Alaska and Hawaii view the entire transit from start to finish. Check Fred Espenak’s great website about eclipses and transits at http://eclipse.gsfc.nasa.gov/ transit/venus0412.html for more material.

You can have your transit and eat it too! The transit of Venus this June 5 will not look as yummy as this pre-birthday cake presented to me by Mark Balanda of Palmyra, PA on June 8, 2004, but it will give readers a little idea of what the phenomenon will look like. There are no second helpings after this event until 2117. Gary A. Becker photo...

822    MAY 20, 2012:   Venus Takes the Plunge

Venus is making its plunge towards the sun as it heads for a near sundown transit across Sol’s disk on June 5. Transits happen when a smaller object like Venus passes in front of a much larger object like the sun. The story leading up to June 5 began when Venus became visible in the western sky late in November of last year. Since December 2011, the Goddess of Love has ranked supreme in the west, tangling with Jupiter in mid-March and reaching its greatest elongation east of the sun on March 27. Since that time, Venus has edged ever closer to the sun, picking up speed as it has approached the Earth. There is nothing strange about what has been happening. It is just a natural consequence of Venus and the Earth circuiting the sun. Venus takes only 225 days to Earth’s year for one orbit. So as we watch Venus from Earth, sometimes we see the planet to the sun’s right and at other times, like now, it is to the sun’s left, what astronomers call an eastern elongation. But soon Venus will move between the Earth and the sun. Almost always the angular tilt of Venus’ orbit to the Earth’s orbit causes it to pass either above or below the sun’s disk. This time around, however, Venus crosses Earth’s orbit while exactly in front of the sun, resulting in a transit. Observers with the proper filtration will get to see a black dot, Venus, moving across the sun’s face. See the May StarWatch articles online at www.astronomy.org. A similar event happened on June 8, 2004. Before that it was 1882, and in the future, this event will not take place again until December 11, 2117. For now, however, sit back and watch as the angular distance between Venus and the sun rapidly contracts. On May 20, Venus is 23 degrees from the sun. By the following week Venus’ distance narrows to 14 degrees. On June 1, Venus is lost in the sun’s glare, ready to transit just four days later.

823    MAY 27, 2012:   Milky Way Awaits

The sun sets in a rural location. The sky darkens, and the stars begin to be revealed, first in a denim lapis sky followed by more points of light as the heavens fuse into a deep cobalt blue, and finally to black. It is a wonderful night to view the Milky Way. Stare as hard as you can, but there will be no faint, gossamer band of light straddling the cosmos, no fuzzy cotton candy path representative of 400 billion stars arching across the boundless sky. It’s May, and you’ve just picked the worst time of the year to view our galaxy because it is surrounding you all the way around the horizon. There is hope, however, because what is down must eventually come up, and what is now on the eastern horizon and nearly invisible is the best that the Milky Way has to offer for the Northern Hemisphere. In the NE after sundown lurk the star clouds of Cygnus, the Swan, which are not quite overhead by dawn. In the east and SE rises the dark rift of obscuring dust from countless supernovae that seems to split our galaxy in two. A little farther south, the swirls and knots of stars and glowing gases mark the broadening bulge of our galaxy which meets the horizon just beyond its widest expanse. If this sounds like a fairy tale, plan a summer sojourn away from the light domes of our cities to a rural locale where stars and horizon meet. Two-thirds of Americans have lost touch with our island universe. Civilization has its perks, but communing with the heavens fills a primordial need as old as humanity. I vividly remember as a teenager one star filled night when through the bare branches of skeletal trees, I spied a white mist encroaching upon my clear sky. I mentally prepared myself for when the haze would obscure everything, but it was moving so slowly. I realized finally that the clouds which would ruin my night were actually the best clouds of the heavens, the star clouds of our Milky Way

Rising Milky Way: In May the Milky Way Galaxy begins to rise in the NE about 11 p.m. with the bright star Vega of Lyra the Harp taking the lead. Here it can be seen silhouetted against Fajada Butte in Chaco Canyon National Historical Park. By dawn when it is arcing over the heavens from NE to S, its photographic appearance will look much more like the image below. Gary A. Becker photography...

The Milky Way from Bryce Canyon, UT: You don’t have to go to one of the ultimate dark sites in the US to view the Milky Way, but it doesn’t hurt. This 2006 digital image was taken shortly before moonset. Gary A. Becker photo...