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Wyoming Skies for May


April 30, 2010 — A monthly look at the night skies of Wyoming, written by Ron Canterna, professor in the University of Wyoming Department of Physics and Astronomy

The prominent summer constellations are previewed in our May skies.

The Big Dipper (Ursa Major) is directly overhead at dusk, with its cup opened northward. The Big Dipper's handle arcs southward in the sky, arriving at Arcturus and ending at Spica. This process is called "arcing to Arcturus." Arcturus is the orange, bright star in the kite-shaped constellation Bootes, the herdsman or "Bear driver."

Later in the early evening, rising above the eastern horizon, the three bright stars of the "summer triangle," Vega, Deneb and Altair, will start their summer celestial ride.

Start saying goodbye to Regulus, the brightest star in the Constellation Leo the Lion, and the Gemini twins, Castor and Pollux.

For planet watchers May is a great treat. Mars and Saturn are aligned along the ecliptic setting late in the mid evening. The brightest object in the western sky after sunset is Venus, now an evening "star."

Peaking at May 5 and 6 are the low frequency Eta Aquarids meteor showers observed before the morning sunrise low and to the southeast. May 19 is the international sidewalk astronomy night when local amateur astronomers will show off their expertise and telescopes. Ask them to show you the wonders of the night skies.

May 2010 Interest: The "outer limits" of the Solar System

In the 1950s the famous Dutch astronomer Jan Oort noted that comets seem to come from all directions and generally from an average position of 50,000 Earth-sun distances (an astronomical unit = AU). Realizing that no comets have origins beyond this region, he proposed a cloud of primeval comets surrounding the sun.

The Oort cloud may have up to a trillion nascent comets. Named after and studied by Gerald Kuiper, a disk-shaped belt of small icy bodies from 30-50 AUs from the sun has been proposed. The Kuiper Belt is estimated to contain more than 35,000 small irregularly shaped objects with dimensions less than 100 km.

Sometimes perturbed from their home by Neptune, some Kuiper-Belt bodies become trans-Neptunian objects, where nearly 1,000 have been charted so far. The Hubble telescope has even discovered several of these objects that are 20 km in dimension.

The Oort cloud and Kuiper Belt objects are not just the most distant objects in the solar system; they are pristine fragments of the original nebula from which the Earth, sun and the entire solar system formed. Their properties and compositions will tell us much about our origins.

For more information, visit the Wyoming Skies home page (http://wyoskies.uwyo.edu) or send an e-mail to canterna@uwyo.edu.


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