Star Cluster Pleiades Sign of Season

 

 

   For the last couple of weeks many of my clear nights have been spent stargazing naked eye or with binoculars in the back yard.  This has been a pleasure especially during the warm spell toward the end of November.

 

   A sure sign of approaching winter is the appearance of the star cluster Pleiades (M45) rising up in the east once twilight fades to darkness this time of year.  Even the nighttime coolness at the end of August seemed to be enhanced when I watch the Pleiades rise up near midnight out of the murky eastern night sky in the late summer.

 

   The Pleiades star cluster, also known as the Seven Sisters, is one of the most beautiful clusters in the night sky.  It is easily identified as it appears as a tiny dipper shape of seven stars. Do not confuse the Pleiades star cluster with the little dipper containing the North Star.  In urban areas usually five stars of this cluster are seen with the unaided eye but under a dark rural sky up to nine stars can be seen.  Binoculars, with their wide field of view, offer the best way to observe this cluster.  Binoculars of the size from 10x to 15x at 50mm aperture reveal the best images of the cluster but the Pleiades are spectacular through any binocular field.  With binoculars the number of stars visible increase to over a hundred.  Under an exceptionally clear and dark sky look closely and you might be able to glimpse filmy wisps of nebulosity surrounding some of the brighter cluster stars.  These gentle clouds of dust and gas are all that remain of a once vast nebula from which the Pleiades were formed.  I find that the thing that makes the Pleiades fascinating is not just the crowded richness of 3rd and 4th magnitude stars but the icy blue colours of the stars.  This young cluster (in astronomical time) is a mere 70 million years of age.  The Pleiades is an open (galactic) group of stars fairly close to us lying at a distance of 440 light years away.

 

   The near full moon passes in front of the Pleiades star cluster twice this month.  We will only be able to see this at the beginning of December when the event occurs at nighttime as the second event occurs during the daytime.  The moon begins to occult (pass in front of) the brighter stars of the Pleiades star cluster on December 3 beginning shortly after 8 p.m..  With the moon very bright now the use of binoculars or telescope will be needed to see the stars disappear behind the moon’s leading dark limb, or what there is of it at this point.  The moon’s trailing (western) limb leaves the brighter stars of the Pleiades around 10:30 p.m..

 

   The Geminid meteor shower is one of the strongest meteor showers of the year.  At a peak of around 100 meteors per hour this shower is not observed as much as the Perseid meteors of August when the weather is warm.  The Geminids peak at the time of year when the nights are clear and cold.  This year they peak on the night of December 13-14.  Geminid meteors are slower moving and more graceful therefore tend to last longer than the meteors of other showers.  The best time to view the Geminid meteors is around midnight when the radiant (point from which the meteors appear to radiate from in the sky) near the star Castor in the constellation of Gemini is high up in the sky.

 

   Saturn is the only planet easily visible this month.  Rising in the east around 11 p.m. at the beginning of December it is easily identified as a bright yellow “star” at a magnitude of 0.4 in the constellation of Leo the Lion.  By month end Saturn will rise by 9 p.m..  The waning gibbous Moon can be seen just above Saturn on the night of December 9.

 

   The winter season officially begins in the northern hemisphere when the sun is at its furthest point south on the celestial sphere.  This, the winter solstice, occurs this year on December 21 at 7:22 p.m. EST.  Our neighbours in the southern hemisphere will be celebrating this event as their first day of summer.     

 

 

Clear Skies

Ted Bronson