The Night Sky of May

Dr. Wayne Wooten
Professor of Astronomy

For May 2011, the Moon will be New on May 3rd. On the first, the waning crescent moon lies just above a fine grouping of four planets in the dawn. Mars stis atop Jupiter, with fainter Mercury just west of them, and bright Venus still farther west. Worth setting the alarm clock to see, about 6-6:15 AM CDT locally. The first quarter moon rises about noon on May 10th. The waxing gibbous moon passes about six degrees south of Saturn in the SE evening sky on May 14. The rose moon, the Full Moon for May, will be on May 17th. The last quarter moon is on May 24, and at month’s end, the waning crescent moon again passes the dawn planets, above Jupiter on May 29, then above the alignment of Mercury, Venus, and Mars on May 30th and 31st.

While the naked eye, dark adapted by several minutes away from any bright lights, is a wonderful instrument to stare up at the Galaxy arching overhead, binoculars are better for spotting specific deep sky objects all along the plane of the Galaxy. For a detailed map of northern hemisphere skies, about April 30th visit www.skymaps.com website and download the map for May 2011; 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 as the next month begins is wonderful video exploring the May sky, available from the Hubble Space Telescope website at: http://hubblesite.org/explore_astronomy/tonights_sky/.

Saturn is the brightest object in the southeast as darkness falls; it lies just above the bright star Spica in Virgo now. 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.

As noted earlier, the other four naked eye planets all lie just west of the Sun in the dawn sky. Several nice groupings of these wanderers occur in May. Mercury passes 1.4 degrees north of brighter Venus in May 8th, and Venus overtakes Jupiter and passes .5 degrees south of it on May 11th, the two brightest planets about a moon diameter apart in the dawn, a nice photo op, since Mercury lies two degrees south of Jupiter at the same time. Then on the 18th, Mercury again passes 1.4 degrees south of Venus, then two degrees south of Mars on the 21st. Venus passes a degree below Mars on the 23rd, and the moon joins the four planets in the dawn by month’s end. To bad all of this dancing isn’t happening in the evening skies, but still some neat groupings for early risers.

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.

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 the triangle of stars that mark Leo’s tail this year. If you instead turn to the handle of the Big Dipper, just south of the end star you can find the famed "Whirlpool Galaxy", M-51, with large binoculars. The spiral arms are resolved with telescopes 8" and larger on dark, clear moonless nights. It has a smaller galaxy colliding with it, creating the tidal distortion as noted in our photo.

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. As noted earlier, Saturn is the only planet now in the evening sky, and is located to the upper right of Spica, and more yellow in color and slightly brighter than Spica as well. 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, just above Saturn.

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