The Sky This Week

Messier 45, the Pleiades star cluster in Taurus, imaged 2017 December 17
with a 10.2-cm (4-inch) f/6.5 Explore Scientific AR102 refractor
and a Canon EOS Rebel SL2 DSLR from Great Meadow, Old Tavern, Virginia.

The Moon returns to the evening sky this week, skirting the southwestern horizon as she draws a bead on dazzling Venus.  She will pass our bright planetary neighbor on between the evenings of the 7th and 8th.  First Quarter occurs on the 11th at 7:46 am Eastern Standard Time. 

This is the week when we exercise the semi-annual ritual of changing our clocks from Daylight to Standard Time.  Technically this is supposed to happen at 2:00 am local time on the 7th, when we set clocks back one hour.  Love it or hate it, almost all of us are required to do it by Federal statute.  15 U.S. Code, chapter 6, subchapter IX §§ 261–264 specifies the rules governing the observance of standard time in the country, including the rules governing the beginning and end of Daylight Time.  Under the current rules, as amended by the Energy Policy Act of 2005, actually place us on Daylight Time for a longer portion of the year than the duration of Standard Time, but there are moves afoot to set us all on one standard time regimen.  Most people prefer having more light in the early evening than in the morning, so Congress is considering setting our clocks to a permanent state of “Daylight Time”.  

The idea of advancing clocks to give us more daylight in the evenings is not new, nor is the idea of “permanent” Daylight Time.  The first year that Daylight Time was enacted was 1918, but it was quickly repealed the following year.  Daylight Time observance became a state and local issue for the next few decades until World War II, when President Roosevelt enacted “War Time”, advancing our clocks for the duration of the conflict.  Local rules returned until 1966, when the Uniform Time Act finally codified Daylight Time in the U.S. Code specified above.  During the “energy crisis” years of 1974 and 1975, daylight Time was enacted in January and February, respectively.
 
The return to Standard Time seems to hasten the seasonal change of the constellations.  If you go out at 8:00 pm Standard Time, the stars of the Summer Triangle seem to suddenly be lower in the western sky, and the stars of winter are rising in the east.  By 10:00 pm Standard Time the stars of the Great Winter Circle are rising in the east, and one feature that has traditionally led those stars is now becoming a prominent feature.  On crisp, clear evenings even suburban skywatchers may notice a small knot of stars that lies just northwest of the bright red-hued star Aldebaran, the fiery “eye” of Taurus, the Bull.  From dark locations the knot resolves into a group of stars that resemble a tiny version of the “Little Dipper”.  These are the Pleiades, or the Seven Sisters, mythological daughters of Atlas and half-sisters of the Hyades, the scattered grouping of stars near Aldebaran.  This diminutive group probably has more folklore associated with it than any other constellation in the sky, with references traceable to almost every culture that has left records of their stories and sagas.  Their name derives from the Greek “plein”, which means “to sail”, since their appearance just before sunrise signaled the opening of the safe sailing season in the Mediterranean Sea.  They form a true star cluster that will reveal more members as one uses optical aids.  Most of us can see six or seven stars with the unaided eye, but people with keen sight may see up to fourteen.  The total number of stars in the cluster is about 1,000.  The cluster’s brightest stars are some of the youngest stars we can see, barely out of the cradle at around 100 million years old.

As mentioned earlier, Venus entertains the Moon as the week winds down.  The pair should make for some nice photo opportunities on the evenings of the 7th and 8th.  Viewed through the telescope, the planet shows a virtually featureless disc that resembles a first quarter Moon.  Her dense, cloudy atmosphere reflects nearly 70 percent of the light that strikes it, which is why she is the third-brightest object in our sky.

Thanks to the clock change, by the week’s end Saturn and Jupiter will be well-placed for viewing during the early evening hours.  Saturn crosses the meridian at around 5:30 pm EST with Jupiter following an hour later.  The two giant planets are on opposite sides of the constellation Capricornus, the Sea-Goat, with Jupiter slowly drifting eastward near the third-magnitude stars Deneb Algeidi and Nashira.  Follow the planet’s progress with a pair of binoculars as he approaches a small arc of fifth-magnitude stars, 42, 44, and 45 Capricorni.