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The Sky This Week, 2019 October 1 - 8

A night to celebrate the Moon!
The Moon, imaged 2019 July 11 from Alexandria, Virginia.
The Moon at age 8 days, imaged 2019 July 11 from Alexandria, Virginia
with a 102 mm (4-inch) f/6.5 Explore Scientific refractor and a Canon EOS Rebel SL2 DSLR.

The Moon wends her way through the southern part of the sky this week, passing the bright planets Jupiter and Saturn before moving into the autumnal constellations.  First Quarter occurs on the 5th at 12:47 pm Eastern Daylight Time.  Luna meets up with bright Jupiter on the evening of the 3rd.  On the night of the 5th she may be found close to golden Saturn.    

October is generally one of my favorite months for observing the night sky.  The weather tends to be clear, the summer’s humidity is all but a memory, the nights aren’t too cold, and the sky is fully dark at a decent hour.  These are the main reasons that the United Nations has designated October 4 – 10 as World Space Week.  This year’s theme is “The Moon:  Gateway to the Stars”, and appropriately October 5th is International Observe the Moon Night.  Throughout the world amateur observers and professional observatories will open their domes to the public to showcase our only natural satellite.  Here in the Washington, DC area there will be a number of venues to get a good look at the Moon.  The University of Maryland will host an open house at its observatory in College Park, MD, while the National Capital Astronomers will have telescopes set up for public viewing near the Nature Center in Rock Creek Park in DC.  Also in DC, the Phoebe Waterman Haas Public Observatory at the Smithsonian’s National Air & Space Museum will be open for lunar views from 7:00 pm until 10:00 pm.  The Northern Virginia Astronomy Club will host its 37th annual Star Gaze at C.M. Crocket Park in Fauquier County, Virginia.  While this day-long event is free, the park has a nominal entry fee.  In all of these events the Moon will be the main attraction, but participants at the NOVAC Star Gaze will also have the chance to see many other celestial objects through a variety of telescopes.  Outside the Washington DC area there will be observing events at science centers and planetariums throughout the country and the world.  Why the Moon?  It is our closest neighbor in space at some 385,000 kilometers (239,000 miles) distance.  Despite this great distance telescopes reveal an astonishing variety of landscapes on Luna’s desolate surface that bear mute testimony to the violent collisions of proto-planetary bodies as the solar system formed.  Take advantage of this opportunity; it only comes once a year!

While the Moon gradually comes to dominate the early evening sky, the late night still affords a chance to view the splendors of the late summer constellations and the rising stars of winter.  From a dark sky site the Milky Way crosses overhead, stretching from the southwest to the northeast horizons.  Sprinkled along the Galaxy’s path are the bright stars of the Summer Triangle, the “W”-shaped constellation of Cassiopeia, the Queen, and the “wishbone” formed by the stars of Perseus, the Hero.  If you follow the left-hand “tine” of the wishbone, you will see a familiar sight of the winter sky rising in the form of the Pleiades star cluster.  Most of us can see six or seven stars in this small grouping, but if you happen to be blessed with sharp eyesight and are under a really dark sky about a dozen stars will reveal themselves.  Look at the Pleiades through binoculars and a dozen more stars will appear, and a good four-inch telescope will bring the count up to around 100!  At a distance of 440 light-years, this is one of the closest galactic star clusters to us.  One of the most striking features of the cluster are its brightest stars, which glow with an icy-blue tint.  These are some of the youngest stars we know of, and they likely formed from a vast cloud of gas and dust some 100 million years ago.  Long-exposure images of the Pleiades show wispy clouds of nebulosity suffused throughout the cluster, the remnants of the cloud of material that formed its stellar cohort.  Despite its diminutive size, the Pleiades cluster figures prominently in the sky lore of just about every culture that can see it.  Even the denizens of J.R.R. Tolkien’s Middle Earth recognized the cluster, calling it “Remmirath”, the “Netted Stars”.

The early evening still hosts the bright glow of Jupiter, but not for very long.  The giant planet sets at around 10:00 pm, so your “window” to see him is becoming more limited.  The best time to get a look at him through the telescope will be during evening twilight before he gets too low and suffers distortion from turbulence in our atmosphere.

As evening twilight fades you will find Saturn just west of the meridian.  The ringed planet still offers a couple of hours of good viewing time before he heels over to the southwestern horizon.  Saturn will be close to the Moon on the 5th, so if you’re attending one of the Observe the Moon Night activities he will add a cosmic bonus to your observing list.