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Jewel Boxes in the Sky

by Geoff Chester, USNO Public Affairs | 03 November 2020

by Geoff Chester, USNO Public Affairs | 03 November 2020

NGC 884 and NGC 869, the "Double Cluster" in Perseus
The "Double Cluster" in Perseus, imaged 2018 OCT 7 from Mollusk, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a Canon EOS Rebel T2i DSLR


The first full week back on Standard Time finds the Moon cruising high on the ecliptic as she wends her way through the rising stars of the winter constellations.  Last Quarter occurs on the 8th at 8:46 am Eastern Standard Time.  Luna begins the week between the “horns” of Taurus, the Bull, then passes through the constellation of Gemini, the twins and the obscure stars of Cancer the Crab.  Early risers will find the Moon passing through the “head” of Leo, the Lion, mid-way between the bright star Regulus and the gold-hued glimmer of Algieba.

“Falling back” to Standard Time is usually a bit of a shock for me.  I enjoy being out under the stars, but usually not until after dinner.  Now the sky is dark when I sit down for my evening meal, and when I do head out with my telescope it’s as if an entire season has suddenly elapsed.  The three stars of the Summer Triangle, Vega, Deneb, and Altair, along with their attendant constellations, are now poised to set, leaving the barren autumn stars patterns to occupy the sky over my yard.  That said, I don’t have to wait too long before the bright stars of winter begin to rise.  One of my favorite sights is the figure of Orion seeming to climb over the horizon, ready to ward off the charge of nearby Taurus.  

High overhead is the diminutive W-shaped group of stars that form Cassiopeia.  This area of the sky is rife with an array of beautiful star clusters that glitter like tiny jewel boxes in the telescope eyepiece.  From a dark site you can see a fairly bright portion of the Milky Way behind the constellation’s main stars that trails off into the neighboring constellation Perseus.  This constellation has a shape that reminds me of the “winner’s portion” of a wishbone, with the bright star Mirfak at the wishbone’s center.  Embedded in the Milky Way between Perseus and Cassiopeia is one of the true treasures of the sky, the “Double Cluster”.

From a dark sky the Double Cluster appears as a fuzzy patch of light to the naked eye, but a pair of binoculars will begin to resolve its starry splendor.  My favorite view is through my 4-inch telescope at low magnification where the two star clusters can be seen in the context of the Milky Way background.  Each cluster resolves into hundreds of stars, and at a distance of some 7500 light years, the brighter members must be enormously luminous to appear as they do in the eyepiece.  Most of the bright stars are blue supergiants, which means that the clusters are quite young on the cosmic scale, forming just 10 to 15 million years ago.  Careful scrutiny will also show a smattering of red supergiant stars scattered between the two main clusters.  These stars are analogous to Betelgeuse in Orion, but they are over five times farther away.  
Shifting our gaze back to Perseus, another much closer star cluster surrounds the constellation’s brightest star, Mirfak.  This group, known as Melotte 20, is widely scattered and is best seen in binoculars.  It is about 510 light-years away. Ten of its members are visible to the naked eye, but binoculars will reveal dozens more.  Most of the stars, apart from Mirfak itself, have a pleasing blue tint.

Returning to Standard Time places Jupiter and Saturn into the early evening sky, and if you wait too long they will be gone for you.  Jupiter sets at around 9:30 pm with Saturn following a bit over 20 minutes later.  Your best views are still in evening twilight, so plan on a late dinner if you still want to see them at their best.

Mars actually benefits from the return to Standard Time.  The red planet crosses the meridian at around 10:00 pm, so you have the best part of the night to give him a look through the telescope.  Keen-eyed observers will note that he is already beginning to fade after his close opposition a few weeks ago, but his disc can still reveal tantalizing features to patient observers.  I enjoy looking at Mars since it is the only place in the solar system other than the Moon and Mercury where I’m looking at a solid surface.  

Venus remains visible before sunrise, glowing brightly among the stars of Virgo.  On the morning of the 5th she passes one degree south of the beautiful second-magnitude double star Porrima.  Closer to the horizon look for the first-magnitude star Spica.  Early in the week the glimmer of elusive Mercury may be seen a few degrees east of the star.


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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