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What's Up In the Sky, May, 2011

posted Apr 26, 2011, 8:57 AM by Marvin Stewart
            On May nights the Big Dipper is high in the north sky and upside down above the Little Dipper. To an older generation of farmers this was a sign of rain. Water would pour out of the dippers bowl onto the Earth below.
            By using the two stars that form the lip of the bowl, Merak and Dubhe, it is easy to find the north star. Just draw an imaginary line from the bottom star, Merak, through Dubhe about five times the distance those two stars are apart and it will end at the north star, Polaris. Don't forget since the dipper is upside down your line is drawn downward.
           The Little Dipper has the honor of having the pole star as the last star in its handle. The first star map that shows Polaris nearest its present position was published in 1518. So if Columbus used it or an empty point just beyond it as north is unknown. Today Polaris is about one and a half full Moon's width away from true north. This isn't a problem for navigators today, nor would it have been in 1492. There are some that believe that the north star is the brightest star in the sky, but it isn't. Polaris is an apparent second magnitude star, and it ranks as the forty ninth brightest star in the sky. In reality it is 2000 times brighter than our Sun, but we are seeing it from a distance of 430 light years away. ( Remember, light years are a measure of distance not time.) Approximately half the stars we see have at least one stellar companion, Polaris has two. The first was discovered by William Herschel in 1780, it is called Polaris AB and is about the same distance from Polaris as the planet Uranus is from the Sun. That fact is made more interesting because it was Herschel that discovered Uranus. It took the Hubble Space Telescope to find the second, Polaris B, which is 100 times further away than AB and takes thousands of years to to orbit Polaris.
           the Big Dipper may be high over head in May but the Full Moon is low in the night sky because it follows the path of the winter Sun. Next Month it will be at its lowest point in the night sky. The last quarter Moon is visible in the day time. Following its path also allows you to trace the path the winter Sun will travel.
          Early risers are in for a treat on May eleventh. Around 4A.M. CDT, the planets Venus and Jupiter will only be about one full Moon distance apart, the closest they will be until 2014.Very nearby will also be Mercury, to the right and below Venus and Mars to the left and below Jupiter. Four planets so close they are almost within the field of view of a pair of binoculars. But don't just wait for the morning of the eleventh. Start looking a few mornings before and keep looking a few days after. This is like watching a parlor trick. It is amazing to watch the planets move when they are this close. There is nothing up my sleeve, no strings attached, but, still they move.
         May 01   Today starting at 2 A.M., the Moon will pass Mercury, then 12 hours later Jupiter and at 3 P.M. CDT, Mars.
                 03    New Moon.
                 06    Eta Aquarid meteor shower peaks.
                 10    First Quarter Moon
                 11    See Venus and Jupiter closest in the early morning sky.
                 17    Full Moon.
                 24    Last Quarter Moon.
                 30    The Moon close to Venus around 11 P.M.