The Sky This Week
U.S. Naval Observatory's Weekly Blog

Treats to See in the Halloween Sky

by Geoff Chester, USNO Public Affairs
26 October 2021

NGC 6960, the "Witch's Broom Nebula" in Cygnus, imaged 2021 October 2
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor,
and a ZWO ASI183 MC CMOS color imager from Great Meadow, Old Tavern, Virginia.
The bright star is 52 Cygni.

The Moon wanes in the morning skies this week, passing through the winter and early spring constellations as her crescent becomes slimmer each day.  New Moon occurs on November 4th at 5:15 pm Eastern Daylight Time. You’ll find Luna near Castor and Pollux, the Twin Stars of Gemini, on the mornings of the 27th and 28th.  Look for the Moon to the north of the bright star Regulus as morning twilight gathers on the 30th.   

As the Moon moves into the morning sky it is time to take a few moments after dark and look up at the stars for science.  The next observing campaign for the Globe at Night citizen-science project begins on the evening of the 27th and runs through November 5th.  This month’s featured constellation is Perseus, The Hero, which may be found rising in the northeastern sky in the mid evening.  To my eyes, Perseus resembles a wishbone with the bright star Mirfak at the juncture of the wishbone’s tines.  The longer tine is formed by an arc of stars that point to the rising Pleiades star cluster, while the shorter one ends in the eclipsing binary star Algol, which fades from magnitude 2.1 to 3.4 every 2.86 days.  Point binoculars at the star Mirfak and you will find it surrounded by a coarse cluster of blue-tinted stars.  Perseus contains a rich range of stars to help determine your local sky brightness; go to the Globe at Night web app to record your observations.
 
The transition from October to November is marked by the annual observance of my favorite “cross-quarter” day, Halloween.  Once an integral part of traditional calendars, cross-quarter days marked the halfway point between the seasonal markers of the equinoxes and solstices.  They were widely observed in many traditions, and were particularly associated with Celtic cultures.  Halloween is derived from a pagan festival called Samhain, which marked the end of the harvest season and beginning of the “darker half” of the Celtic year.  As Christianity spread throughout northern Europe Samhain evolved into the Christian feast of All Saint’s Day, which was celebrated on November 1st.  The older darker aspects of Samhain were still celebrated on the previous evening as All Hallows Eve when the spirits of those who had died during the previous year were believed to roam among the living.  Lamps were lit to guide the souls to their kin, and feasts were prepared to give everyone sustenance.  Here in the U.S. Halloween is the most widely observed of the cross-quarter days.  Two others may still be found on our calendars as Groundhog Day and May Day.  The fourth one, Lammas, is still celebrated in parts of Europe, but it isn’t well known on our side of the Atlantic Ocean.

The night sky of Halloween is one of transition.  The stars of the Summer Triangle are still prominent in the early evening, and by 10:00 pm the Great Square of Pegasus crosses the meridian.  By midnight the bright stars of the winter sky are rising in the east, anchored by the dominant constellation of Orion.  It won’t be very long before Orion and his cohorts illuminate the longest nights of the year!

The dazzling planet Venus reaches her greatest elongation from the Sun on the 29th.  Despite this, she isn’t far above the southwest horizon as evening twilight fades.  This is due to her far southerly declination, which is at its lowest point for the current apparition.  She will begin to climb northward over the next few weeks, but by mid-December she will start to move toward the advancing Sun.

Saturn and Jupiter keep watch over trick-or-treaters as they prowl the neighborhoods on Halloween.   Both planets are well-placed near the meridian at 8:00 pm local time.  If you have a telescope, this is a great opportunity to provide your ghoulish visitors with an extra treat in addition to candy.  Saturn’s rings and Jupiter’s four bright moons will be easy to spot, just beware of flying witches.

You still have a chance to glimpse the elusive planet Mercury in the brightening sky of morning twilight.  The fleet world is making his last good appearance for Northern Hemisphere observers for this year.  He is located about 30 degrees south of the bright star Arcturus and should appear brighter than the star.
 
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