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The Night Sky of May

Dr. Wayne Wooten
Professor of Astronomy

For May 2010, the Moon will be waning gibbous on May 1st, with full moon on April 28th. The last quarter moon rises about midnight on May 6th. The waning crescent moon passes about six degrees north of Jupiter in the morning sky on May 9th, then seven degrees north of Mercury in morning twilight on May 12th. The new moon occurs on May 14th, and it will wax in the evening sky in the last two weeks of this month. On May 16th, the waxing crescent moon with earthshine on its upper dark side passes close to Venus in the western evening sky. The first quarter moon passes Mars almost overhead on May 20th, and then passes seven degrees south of Saturn in the southeast on May 22nd. The rose moon, the Full Moon for May, will be on May 27th.

To the west, Venus dominates the twilight until well into fall. It is still small and almost fully lit in the telescope. It passes the Pleiades cluster on April 25th, and then six degrees north of orange Aldeberan, the eye of Taurus the Bull, on May 3rd. Mars is overhead and still conspicuously bright and red, but fading fast as the earth leaves it behind. It moves from Cancer into Leo, approaching the bright star Regulus as May ends. It is so distant and small that our telescopes will hardly show more than a red ball and perhaps some polar caps. It was much closer, bigger, and brighter in our scopes at the end of January, when the earth passed it at opposition.

Saturn is the brightest object in the southeast as darkness falls. Its rings are now opened up to eleven degrees, much more visible than when they were edge-on during last year's Saturnian Equinox. You may also see some belts and zones on the planet's disk. The largest moon, Titan, will be seen in any small telescope, but others will need larger scopes to spot. As the planet is now only half are bright as when the bright rings are tilted more open, up to six moons may be spotted, in a straight line with the rings, with an eight inch telescope.

The winter constellations will soon be swallowed up in the Sun's glare, but Orion is still visible, with its famed Orion Nebula, M-42, seen below the three stars marking his famed belt. Dominating the southwest is the Dog Star, Sirius, brightest star of the night sky. When Sirius vanishes into the Sun's glare in two months, this sets the period as "Dog Days".

The brightest star in the NW is Capella, distinctively yellow in color. It is a giant star, almost exactly the same temperature as our Sun, but about 100X more luminous. Just south of it are the stellar twins, the Gemini, with Castor closer to Capella, and Pollux closer to the Little Dog Star, Procyon. Mars was just east of the twins for the last few months, but has now moved eastward toward Leo the Lion as it orbits the Sun.

Overhead, the Big Dipper rides high. Good scouts know to take its leading pointers north to Polaris, the famed Pole Star. For us, it sits 30 degrees (our latitude) high in the north, while the rotating earth beneath makes all the other celestial bodies spin around it from east to west. If you drop south from the bowl of the Big Dipper, Leo the Lion rides high. Note the Egyptian Sphinx is based on the shape of this Lion in the sky. Saturn lies just SE of triangle of stars that mark Leo's tail this year.

Taking the arc in the Dipper's handle, we "arc" SE to bright orange Arcturus, the brightest star of spring. Cooler than our yellow Sun, and much poorer in heavy elements, some believe its strange motion reveals it to be an invading star from another smaller galaxy, now colliding with the Milky Way in Sagittarius in the summer sky. Moving almost perpendicular to the plane of our Milky Way, Arcturus was the first star in the sky where its proper motion across the historic sky was noted, by Edmund Halley. Just east of Arcturus is Corona Borealis, the "northern crown", a shapley Coronet that Miss America would gladly don, and one of few constellations that look like their name. The bright star in the crown's center is Gemma, the Gem Star.

Spike south to Spica, the hot blue star in Virgo, then curve to Corvus the Crow, a four sided grouping. It is above Corvus, in the arms of Virgo, where our large scopes will show members of the Virgo Supercluster, a swarm of over a thousand galaxies about 50 million light years away from us. One of the most photogenic members is the Needle Galaxy, NGC 4565, seen almost edge on the phot. It lies just north of Virgo in Coma Berenices, a historic constellation.

When the Pharaoh of Egypt Ptolemy III went off to battle, his queen Berenice vowed to cut off her long tresses as a sacrifice to Venus, should he come back safe. Upon his triumphant return, she donated her hair, but it then vanished from the temple. The fast thinking priest of Venus assured her that Zeus himself had taken her hair and placed it among the stars, pointing to this faint cluster of stars north of Virgo as the site it had been saved to in the heavens. It was a story that saved the careless priest's life, made the queen and hubby happy, and gave us a constellation filled with faint fuzzy galaxies to enjoy.

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