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Northern Rockies Skies for January: Auriga, the Charioteer

December 19, 2013

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.

Named for its stars outlining a pointed helmet of a charioteer, the winter constellation Auriga is best seen directly overhead around 10 p.m. during January. Auriga also denotes the location of the anticenter of the Milky Way galaxy. Its brightest star, Capella, is the sixth brightest star in the sky and third brightest in the northern hemisphere. Capella, a multiple star system about 40 light years away from the sun, is part of the Hyades moving cluster of stars, the nearest moderately aged cluster of stars.

The second brightest star in Auriga, Menkalinan, is a triple star system located about 80 light years from the sun. Menkalinan belongs to the Ursa Major moving star group that is made up from many stars in the Big Dipper. Due to its position in the galaxy, there are only a few open clusters of stars and very few nebulae in Auriga.

January 2014 Interest: Famous Astronomers: Isaac Newton III -- Optics

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Newton's work spanned the flowering of experimental science in the Age of Reason and the gradual disappearance of pseudosciences such as alchemy, which included the search for methods that might transmute baser metals into gold. Yet, it was his interest in the quests of alchemy that, to some degree, motivated Newton's revealing experiments in optics.

Newton adhered to "corpuscularianism,” part of the dogma of alchemy, that viewed light as particles subtler than particles of matter, and as divisible into finer pieces (unlike the theory of atoms, which were conceived as indivisible). This viewpoint led Newton to experiments with prisms, whereby he showed definitively that prism-refracted light spread out into the colors of the spectrum -- red to violet -- refuting Aristotle’s long-standing theory that light was white or colorless and that colored light was caused by interaction with the darkness of matter.

Instead, Newton's experiments showed that the colored light reflected from different materials was the result of differential absorption by matter of the pure spectral hues. For example, the perceived color sensation of purple arises from the combination of red and violet hues reflected from material substances.

Newton published this correct theory of color in his book “Opticks” (1704), along with experimental results and several other conjectures, including the idea of diffraction of light that arises from closely spaced optical elements. However, his work did not advance the additional modern understanding that light has a wave-like nature as well. Two more centuries elapsed before elucidation of the full theory of light by quantum mechanics -- the understanding that light behaves both like waves and particles (Newton's corpuscles, which we now call photons).

Alchemy's failed searches for a method to transmute one element into another also awaited the era of modern physics, when astrophysicists' cousins -- the first particle physicists -- discovered radioactivity and the nuclear processes of fission and fusion, the latter being the process that powers stars.

The wavelength-dependent refraction that light suffers when passing through glass lenses ("chromatic aberration") prompted Newton to invent a telescope using a mirror as the primary objective element -- the Newtonian reflector -- the fundamental construct behind today’s large, modern reflecting telescopes.

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

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