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The Sky This Week, 2018 November 6 - 13

Scoping out autumn's best sights
Messier 27, the Dumb-bell Nebula, imaged 2018 October 7 from Mollusk, Virginia.
Messier 27, the Dumb-bell Nebula, imaged 2018 October 7 from Mollusk, Virginia
with an Explore Scientific AR-102 102mm (4-inch) f/6.6 refractor telescope and a Canon EOS Rebel T2i DSLR.

The Moon returns to the evening sky this week, waxing through her crescent phases as she moves along the southern reaches of the ecliptic.  First Quarter occurs on the 15th at 9:54 am Eastern Standard Time.  Look for the Moon close to the planet Saturn in the southwest during the early evening hours of the 11th.  Luna ends the week drawing a bead on ruddy Mars.

Now that we’re back on Standard Time we have ample time to get out and have a nice evening under the stars and still retire at a decent hour.  Astronomical twilight now ends at around 6:30 pm, offering several hours of darkness to explore some of the wonders of autumn’s crisp skies.  It’s one of my favorite times to visit some of the best celestial objects available to owners of small telescopes.  There are a number of “showpiece” objects representing many different types of “deep sky” objects spread across the sky at this time of year, and you can visit all of them over the course of a couple of hours.  The first thing to draw your attention is the Milky Way, which bisects the sky from the southwest to the northeast.  Many of the best star clusters and nebulae can be found along its luminous path.  You can spot many of these as bright concentrations of stars in binoculars, and a low-power telescope can pick up some of the brighter glowing nebulae.  One of the best of the latter is located just over 8 degrees southeast of the star Albireo, which lies almost at the center of the Summer Triangle asterism.  Located in the obscure constellation of Vulpecula, the Fox, Messier 27 looks like a pale puff of smoke set in a dense field of background stars.  This object, popularly known as the “Dumb-bell Nebula” due to its bi-lobed shape, is one of the brightest and closest of the so-called “planetary nebulae”.  These objects are the remnants of low-mass evolved stars that have undergone a core collapse.  The central star is a hot white dwarf emitting copious amounts of ultra-violet radiation, causing the surrounding shell of tenuous gas to glow.  Our next target is Messier 15, a globular star cluster located just four degrees northwest of the second-magnitude star Enif, which crosses the meridian at around 6:45 pm.  M15 is a tightly-bound mass of hundreds of thousands of stars that will easily resolve in a 4-inch aperture telescope.  Globular clusters contain some of the oldest stars in the universe and probably represent the cores of dwarf galaxies that have passed multiple times through the dis of the Milky Way.  It is located about 30,000 light-years from Earth.  By 8:30 pm the Great Square asterism that forms part of Pegasus is crossing the meridian.  Extending northeast from the star Alpheratz, which marks the upper left corner of the square, is a diverging chain of stars.  “Star-hop” to the second star in the brighter chain, then hop up past two fainter stars.  Under a dark sky you should see what looks like a small detached part of the Milky Way.  This is Messier 31, the Great Andromeda Galaxy, the closest large galaxy to our Milky Way.  This soft glow is the combined light of some 300 billion stars that’s located around 2.5 million light-years away.  It’s a stunning sight in binoculars that only gets better with the use of larger instruments.  A good 3-inch telescope should reveal two of the galaxy’s dwarf elliptical galaxy companions.  Our final showpiece is high in the northeast by 9:00 pm and is located in the Milky Way between the W-shaped constellation of Cassiopeia and the bright star Mirfak in Perseus.  Binoculars will show two bright knots of light which will each resolve into hundreds of stars in the telescope.  Known as the Perseus Double Cluster, it is one of my favorite objects to show to first-time telescope visitors.

We’re now down to just two bright planets to look for in the evening sky.  Jupiter is now lost inn evening twilight and will pass behind the Sun on the 26th.  That leaves Saturn and Mars to mind the evening hours.

Saturn hangs low in the southwest as twilight fades.  He sets at around 8:00 pm, so you don’t have much time to catch a glimpse of him in the telescope.  You’ll find him just west of the thin crescent Moon on the evening of the 11th. 

Mars crosses the meridian at around 7:00 pm.  He continues to trek eastward against the faint stars of the autumn constellations and steadily moves away from the third-magnitude star Deneb Algedi.  By the end of the week he enters the bounds of the constellation Aquarius, the Water Bearer.  His small disc now shows a distinct gibbous phase in the telescope eyepiece.

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