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The Sky This Week, 2018 October 23 - 30

Hanging on to summer's stars.
The Summer Triangle, imaged 2014 June 2 from Sky Meadows State Park, Paris, Virginia
The Summer Triangle, imaged 2014 June 2 from Sky Meadows State Park, Paris, Virginia
30-second unguided exposure @ISO1600 with a Canon EOS Rebel T2i DSLR.

The Moon moves into the rising stars of the winter sky this week, waning from the Full Hunter’s Moon to the Last Quarter phase, which will occur on the 31st at 12:40 pm Eastern Daylight Time.  Late-night skywatchers can see Luna pass in front of the scattered stars of the Hyades star cluster on the night of the 27th and wee hours of the 28th. 

The Moon’s bright glow washes out the view of the sky’s fainter stars and the Milky Way early in the week.  For these evenings you’ll have to be content with looking at the sky’s brighter stars, but we still have some of summers brighter constellations to enjoy in the evening hours.  High overhead in early evening are the three stars of the Summer Triangle asterism, Vega, Deneb, and Altair.  Two of these stars, Vega and Altair, are among the closest bright stars to the Earth.  Vega, brightest and westernmost of the trio, is just 25 light-years distant and glows with a distinct blue hue.  It’s one of my favorite stars to look at in a small telescope thanks to this distinct color.  A low-power telescope or binoculars will show the remaining stars of Vega’s compact constellation of Lyra, the harp.  These stars form a small parallelogram that extends southeast from Vega.  Just to the northeast of the bright star you may notice a close pair of stars in your binoculars.  This wide pair is known as Epsilon Lyrae, and each component is itself a close double star that can be split with a good three- or four-inch telescope.  The four stars comprise the so-called “double-double”, one of the most popular targets for amateur astronomers.   Moving on to Altair, southernmost star in the Triangle, we find a bright whitish star that’s located a mere 16 light-years away.  Look about 12 degrees east of Altair for another compact constellation, Delphinus the Dolphin.  This is a wonderful little star pattern, easily visible in binoculars, that consists of a compact rhombus of stars trailed by a pair of trailing stars.  It’s not difficult to imagine a tiny dolphin leaping up from a starry ocean below.  The final star in the triangle is Deneb in the constellation of Cygnus, the Swan.  It’s almost as bright as its companions, but it is over 100 times more distant than Altair!  There’s one more first-magnitude star to find in the evening sky, but it’s one that not many people notice.  You’ll find it on the meridian about 20 degrees above the southern horizon at around 10:00 pm.  This star is Fomalhaut, brightest star in the very obscure constellation of Pisces Austrinus, the Southern Fish.  Fomalhaut is also just 25 light-years away, and it is the subject of intense study due to a surrounding “debris disc” that has been imaged directly by large earth-based telescopes.  Images made with the Hubble Space Telescope have revealed a planet within this disc, so Fomalhaut is the first star to reveal its planetary system directly to our astronomical instruments.

You can still catch Jupiter low in the southwest during fading evening twilight.  Old Jove now sets just over an hour after the Sun, and while you might be able to catch a glimpse of him in the telescope before he sets, turbulence in our atmosphere will render him as little more than a cream-colored blob.

You’ll have better luck with an early evening view of Saturn.  He, too, is low in the southwest as twilight fades, but you’ll have about an hour after twilight ends to get a good look at him before he also settles into the turbulence above the horizon

Mars marches steadily eastward through the stars of Capricornus.  By the end of the week he approaches the third-magnitude star Deneb Algedi, the “Tail of the Goat”.  Mars is now the brightest planet that you can see during the evening and late-night hours, and he is easily identified by his subtle pink hue.  His disc, now half the apparent size that it was at opposition, will show a noticeable gibbous phase when viewed in a telescope.

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