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The Shapes of the Seasons

Oct. 11, 2022 | By Geoff Chester

Saturn, 2022 October 11, 01:16 UT
Imaged from the U.S. Naval Observatory, Washington, DC
with the historic 1895 12-inch Clark/Saegmüller refractor

The Moon wanes in the late evening and early morning sky this week, climbing to the northern reaches of the ecliptic as she passes through the rising winter constellations.  Last Quarter occurs on the 17th at 1:17 pm Eastern Daylight Time.  Luna rises with the Pleiades star cluster late in the evening of the 12th.  On the morning of the 15th she forms a compact tringle with the star El Nath, the star that marks the northern “horn” of Taurus, the Bull, and ruddy Mars.  By the week’s end you will find the Moon near Castor and Pollux, the “Twin Stars” of Gemini, as morning twilight gathers.

As Luna slips into the morning sky we once again have a great view of the departing constellations of summer and the more subdued star patterns of autumn.  By 8:00 pm EDT the stars of the Summer Triangle asterism crosses overhead.  From dark sky observing sites the Triangle is bisected by the softly glowing star clouds of the Milky Way.  The brightest parts of our home galaxy still linger in the southeast, where you can still spot the “Teapot” asterism of Sagittarius, the Archer.  Just above the Teapot’s “spout” you will find the brightest and densest part of the Milky Way, indicating the direction to the center of the Galaxy some 30,000 light years away.  We don’t actually see this mass of billions of stars, though.  The “wall” of stars that form the Sagittarius star cloud is about 8000 light years distant, backed by huge clouds of cool opaque gas and dust.  You can clearly see this dark material as a “rift” that can be traced back up through the constellation of Cygnus.  This stretch of the Milky Way is speckled with bright glowing knots that reveal star clusters and glowing gaseous nebulae that can be picked out with a pair of binoculars.

As the Summer Triangle heels over toward the west, the sky becomes a bit less flashy.  By 10:00 pm another geometric figure approaches the meridian.  Four second-magnitude stars form the Great Square of Pegasus, the winged horse of classical Greek mythology.  Now that we’re in the playoff stage of baseball season, it seems entirely appropriate to have a diamond in the sky.  Where the Summer Triangle abounds with star clusters and glowing gas clouds, the Great Square offers a “window” into intergalactic space.  We are looking away from the disc of the Milky Way as we gaze in the direction of Pegasus, so any fuzzy patches of light that waft through the telescope eyepiece are distant cousins of our home galaxy.  One of these, located in the constellation of Andromeda off the northeast corner of the Square, is even visible to the unaided eye on a clear night under dark skies.  

As midnight approaches, the arc of the Milky Way passes high overhead.  Located in its path is a small constellation that resembles the letter “W”.  This is Cassiopeia, another character in the Greek myth that includes Pegasus and Andromeda.  Once again the backdrop of Cassiopeia includes star clusters and glowing nebulae.  It is one of my favorite areas of the sky to explore with a wide-field telescope.

Saturn is well placed for viewing during the early evening hours.  You will now find the ringed planet near the meridian at around 9:00 pm local time.  The planet’s low declination limits the amount of time you have to look at him with minimal distortion from turbulence in the Earth’s atmosphere, but when you catch those moments of steady air the view is always striking.  A six-inch aperture telescope will show the planet, surrounded by the subtly colored rings, floating among a bevy of its icy moons.  It’s a view that, to me at least, never gets old.

Jupiter grabs your attention almost immediately after sunset.  Old Jove outshines everything in the night sky after the Moon and Venus.  Even in proximity to the full Moon, Jupiter isn’t overwhelmed by Luna’s brilliant glow.  Jupiter reflects more than half of the sunlight that strikes him, and his enormous girth sends lots of photons our way.  Small to modest telescopes are best to show off his darker cloud belts; in larger instruments he is almost too bright!
 
Ruddy Mars is rapidly slowing his eastward progress against the stars.  This week he forms a large triangle with the bright stars Capella and Aldebaran.  Note the red planet’s similar hue compared to Aldebaran and the contrast with the yellow light of Capella.
 
 
Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529