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Northern Rockies Skies for July

June 28, 2012

A monthly look at the night skies of the northern Rocky Mountains, written by astronomers Ron Canterna, University of Wyoming; Jay Norris, Challis, Idaho Observatory; and Daryl Macomb, Boise State University.

This month presents the Milky Way galaxy in all its splendor.

The constellation Scorpius, located right above the southern horizon, can be seen. Search for its red supergiant, Antares. Above Scorpius is Ophiuchus, also known as “the serpent-bearer." It is accompanied by the fainter and smaller constellation Serpens, referred to as “the snake.” Nearly overhead, one hour after sunset, is the constellation Hercules, “the strongman.”

Look midway between the southern horizon and the zenith with binoculars so you can see several star clusters, hundreds to thousands of stars that are held together by their own gravitational attraction. Now, turn to the east where Cygnus, “the swan,” also sometimes referred as the Northern Cross, guides the eye through a major section of the plane of our Milky Way galaxy. Midway between Cygnus and Hercules is the tiny constellation, Lyra, with the brilliant bluish-white star known as Vega.

With binoculars, you may see the Ring Nebula M 57 just a few degrees southeast of Vega. To the north, on the northern horizon, is Cassiopeia that appears as a great “W” in the sky. The Milky Way is brilliantly displayed through the constellations Scorpius-Cygnus-Cassiopeia.

Planet alert: Keep your eye on Saturn and Mars near Spica, in Virgo at sunset. The morning star, Venus, with its companion, Jupiter, rises about two hours before sunrise.

Famous Astronomers: Laplace
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History remembers the mathematician and astronomer Pierre-Simon Laplace (1749-1827) as being born of ordinary circumstances in Beaumont-en-Auge, Normandy. However, his natural analytic abilities were recognized early on, and resulted in his introduction to a famous mentor, the mathematician and physicist Jean le Rond d'Alembert. This assured Laplace's placement at a university and further development of his skills. His contributions across many disciplines account for Laplace, the “Newton of France,” being regarded as one of the greatest scientists of all time, and probably the greatest of the Napoleonic era.

His earliest works expanded on the nebular hypothesis for the origin of solar system, and developed mathematics on quasi-stability of the solar system (although the motions of the planets are now known to be chaotic over sufficiently long time scales). His study of planetary motions led him to be the first to suggest (correctly) the possibility that Newton's law of gravitation did not act instantaneously over finite distances.

Laplace also was the first to anticipate the concept of black holes -- stars so massive that light could not escape from their surfaces. Although ownership of the idea of (gravitational, electrical and fluid) potential functions is now understood to be distributed among several mathematicians of the 18th century, Laplace contributed much to the formal development of potential theory via the calculus. Laplace (along with Kant) suggested that some nebulae might be external to the Milky Way, and are galaxies in their own right -- predating 20th century verification by Edwin Hubble and others.

Laplace contributed a vast body of analytical work -- foundations to mathematical and engineering physics, including the famous Laplace transform. But he often was known for incomplete descriptions of his analysis, sometimes settling for essential sketches rather than complete proofs of his discoveries, the mark more of a physicist than that of a mathematician. However, Laplace did help to develop the Bayesian theory of probability.

Perhaps Laplace's most enduring quote is, "The weight of evidence for an extraordinary claim must be proportioned to its strangeness."

To view this month's sky chart, click here.

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