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The Sky This Week, 2018 January 8 - 16

Watch out for the Hunter.
Orion and environs
imaged from near Morattico, Virginia on 2016 January 3.

The Moon is visible before sunrise this week, waning through her crescent phases as she dips low along the path of the ecliptic.  New Moon occurs on the 16th at 9:17 pm Eastern Standard Time.  Luna and the planets Mars and Jupiter deliver a fine photo opportunity for early risers on the 11th, forming a tight triangle in the gathering twilight. 

This week finds some 3000 astronomers from around the world converging on the Washington area for the 231st Meeting of the American Astronomical Society.  2017 was a year full of exciting announcements ranging from the first detected collision between neutron stars to the discovery of the first interstellar asteroid.  The latest results from ongoing planetary exploration missions, high-energy astrophysics, and instrumentation will highlight the week’s proceedings.  Among the highlights is a public talk by the editors of the popular Astronomy Picture of the Day website entitled “The Year’s Best Astronomy Images”.  While pictures made with the Hubble Space Telescope grab most of the public’s “wow” reactions, the work of many dedicated astro-imagers give the HST a good run for the money.  The talk will be held on the evening of the 9th at 7:00 pm EST at the meeting’s site at the Gaylord National Hotel at National Harbor.

January’s evening skies are dominated by the impressive collection of stars that make up the constellation Orion and the surrounding bright stars of the Great Winter Circle.  The long, chilly nights are lit by the glow of 9 of the 25 brightest stars in the entire sky, with Orion serving as a sparkling centerpiece.  Visible from virtually every inhabited place on the Earth, Orion is one of the oldest star patterns that we can find in ancient records.  He occupies a prominent place in the mythology of many past civilizations with his oldest descriptions dating to the Old Kingdom of Egypt, where he was identified as Osiris, god of the underworld.  By the time of the Fifth Dynasty the pharaoh was believed to transform into Osiris upon his death, and in the famous “pyramid texts” this transformation is incorporated into the king’s mortuary cult.  The origins of this transformation probably date back to early dynastic times around 3200 BCE.  Our “modern” skylore, which derives from Greek and Roman traditions that are almost 2000 years old, depicts Orion as a Hunter, but he has no prominent place in their legends.  Orion is perhaps the most widely-recognized star pattern in the sky, with the bright red-tinted star Betelgeuse and the ice-blue star Rigel separated by the three “belt stars” Alnitak, Alnilam, and Mintaka.  Most of Orion’s stars are very far away at distances of over 1000 light-years, which means that they are highly luminous.  Alnilam, the middle star in Orion’s belt, is some 300,000 times more luminous than our Sun!

Orion is a wonderful constellation to explore with binoculars or a small telescope.  From the city you can admire the beautiful blue colors of the belt stars and Rigel, which contrast with the distinctive red-amber hue of Betelgeuse.  From a dark location the constellation’s fainter stars come out, and careful scrutiny of the stars that form the diminutive “sword” under the belt stars will show the fuzzy glow of the Great Nebula set in a grouping of blue-tinted stars.  Direct a small scope at the nebula and you’ll see swirling clouds of glowing gas surrounding a heart of four bright stars that are newly-born from the surrounding gas and dust clouds.  Long-exposure images from dark skies show the entire constellation suffused with the glow of star-forming nebulosity.  It’s one of the most active star-forming regions in our Galaxy.

The morning sky is where you’ll now find the elusive planets.  The easiest ones to spot are Jupiter and Mars.  The red planet passed Old Jove at the end of last week, and he will soon abandon his giant rival.  This will take a few weeks to play out, but this week you’ll get a fine chance to see the pair with the waning crescent Moon.  Mercury, Venus, and Saturn remain too close to the Sun to easily see before daybreak.

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