A Mini Tour of the Late Summer Sky

Late_Summer_StarsSummer’s getting long in the tooth in the northern hemisphere, but don’t give up on stargazing just yet. The Milky Way from Cygnus through Sagittarius remains visible during the longer nights. In the image above, for example, you see a patch of sky that’s particularly rewarding for observers with just a short time for stargazing. This part of the sky, which includes the constellations Ophiuchus and Aquila, is strewn with star clouds, open star clusters, and nebulae. It beckons stargazers in the northern and southern hemispheres to grab some good optics and take a closer look.
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Star Factories in Sagittarius

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Composite image by Terry Hancock of star forming regions in the constellation Sagittarius

The golden age of star formation in the Milky Way is long past, but there’s still plenty of activity in dusty spiral arms of the Milky Way. In this astonishing wide-field composite image by astrophotographer Terry Hancock of Downunder Observatory, for example, you see a half dozen emission nebulae in the Sagittarius Arm of our galaxy in which new stars ignite and set aglow the clouds of gas and dust from which they form.

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The Lazy Person’s Guide to Dark Matter, Part 2

abell-383-galaxy-clusterIn the first part of this ‘lazy person’s guide to dark matter’, you learned of the unsettling conclusion that four-fifths of the matter in the universe is unidentified, revealing its presence not by emitting or absorbing light but by exerting through gravity an influence on the motion of galaxies and galaxy clusters. All attempts to explain this so-called “dark matter” in terms of known particles and objects– everyday atoms and molecules, dust, dark stars, and rogue planets– have so far failed, and astronomers and physicists have slowly turned to more exotic possibilities to account for dark matter. Although dark matter remains unexplained, observations and calculations of galaxy motion and the structure of the early universe have given astronomers a good idea of its key properties. Particles which are candidates for dark matter must be…

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The Sky This Month – August 2014

perseidThe thickest region of the Milky Way in Scorpius and Sagittarius reaches its highest point above the southern horizon in the mid-evening hours for northern stargazers in August, and it remains high overhead in the south.  The Perseid meteor shower builds slowly during early August and peaks before dawn on the 12th.  This year, the nearly-full Moon will obscure the Perseids at their peak. So have a look earlier in the month, after midnight after the Moon has nearly set, for this reliable and active meteor shower.  And if you don’t mind rising before dawn, you can see the planets Venus and Mercury make their closest apparent approach since 2000. Here’s what to see in the night sky this month…

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Miss Leavitt’s Stars and the Size of the Universe

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Henrietta Leavitt

Nature does not give up her secrets easily. But sometimes, with great skill and effort, someone makes a truly important discovery and reveals knowledge even the wisest philosophers once believed to be beyond the reach of mankind.

The composition of stars is one example.  In 1835, the French scientist Auguste Comte declared the composition of stars to be an example of knowledge forever beyond human understanding.  Just a few years after Comte’s death, 19th century astronomers carefully measured starlight with spectroscopes and discovered that stars are made of the same material found on Earth… hydrogen and carbon and oxygen, and other common elements.

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