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The Night Sky of May

Dr. Wayne Wooten
Professor of Astronomy

For May the waning crescent moon passes just south of Venus in the dawn, both rising about 5 a.m.. The moon is new on May 4th. The waxing crescent passes three degrees south of Mars on May 7th. The first quarter moon is May 11th, and the May full moon, the Flower of Strawberry Moon, is on May 18th. The waning gibbous moon passes just south of Jupiter on the morning of May 20th, then even closer to Saturn on May 22nd. The last quarter moon is on May 26th.

While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up into deep space, far beyond our own Milky Way, binoculars are better for spotting specific deep sky objects. For a detailed map of northern hemisphere skies, about April 30th, visit the www.skymaps.com website and download the map for the new month; it will have a more extensive calendar, and list of best objects for the naked eyes, binoculars, and scopes on the back of the map. Also available is wonderful video exploring the sky, available from the Hubble Telescope website at: www.hubblesite.org.

The May meteor shower is the eta Aquariids. They will be active from May 1st to the 28th. The Eta Aquariids are a strong shower when viewed from the southern tropics. From the equator northward, they usually only produce medium rates of 10-30 per hour just before dawn. Activity is good for a week centered the night of maximum activity. These are swift meteors that produce a high percentage of persistent trains, but few fireballs.

A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky called Radiant. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. The Meteor Data Center of the IAU lists over 900 suspected meteor showers of which about 100 are well established. To keep up to date on the latest meteor shower visit www.amsmeteors.org.

Mercury and Venus are both too close to Sun to be easily seen this month. Mars is the only evening planet, faint and distant in the west, moving from Taurus into Gemini by midmonth. As May begins, Jupiter rises in the SE in Ophiuchus about midnight, and about 10 p.m. by month’s end. Saturn is farther east in teapot of Sagittarius, and rises about two hours later. Both will be well placed for evening gazes by mid June.

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 Northwest 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.

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.

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 shapely 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. Note Jupiter now near Spica. The arms of Virgo harbor the Virgo Supercluster of Galaxies, with thousands of "island universe" in the Spring sky.

To the northeast Hercules rises, with his body looking like a butterfly. It contains one of the sky’s showpieces, M-13, the globular cluster faintly visible with the naked eye. Find it with binoculars midway on the top left wing of the cosmic butterfly, then take a look with a larger telescope and you will find it resolved into thousands of stars!

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