Messier 45, The Pleiades, imaged 2017 December 17 from Great Meadow, Virginia
with an Explore Scientific AR102 10.2-cm (4-inch) f/6.5 refractor and a Canon EOS Rebel T2i DSLR
"Many a night I saw the Pleiads, rising thro' the mellow shade,
Glitter like a swarm of fireflies tangled in a silver braid."
Alfred, Lord Tennyson - Locksley Hall
The Moon returns to the evening skies this week, waxing through her crescent phases as she climbs through the faint autumnal constellations. First Quarter falls on the 21st at 11:45 pm Eastern Standard Time. Luna starts the week near Jupiter and Saturn, appearing closest to the pair of planets on the evening of the 19th. By the week’s end she will approach the ruddy glimmer of Mars.
If you have an unobstructed view of the northern horizon, this is the time of year when the familiar asterism known as the Big Dipper reaches its lowest point in the sky, scraping the tree-line in its endless journey around Polaris, the North Star. The seven stars of the Dipper are the brightest members of the larger constellation of Ursa Major, the Great Bear. Our present association of a bear with these stars has a long tradition dating back at least to classical Greek times, and it may possibly date back even further to folklore that developed in prehistory. Many cultures in the Northern Hemisphere identify it as a bear, including many Native American peoples. One of my favorite stories comes from the Iroquois people who inhabited much of the northeastern U.S. before Europeans arrived. They saw the four stars of the “bowl” of the Big Dipper as a bear, while the three stars of the “handle” represented three hunters. The hunter closest to the bear carried a bow and arrows, while the hunter at the end of the “handle” carried firewood. The star we now call Mizar, which forms the bend in the “handle”, was a hunter who carried a pot, represented by the naked-eye companion to Mizar, the star Alcor. Every year the hunters pursued the bear around the pole, and each autumn, as the bear neared the northern horizon, they caught it and cooked it in the pot. The blood from the bear’s arrow wounds dripped down to Earth, staining the trees red and causing the leaves to fall. The hunters, in turn, had a well-stocked larder for the coming winter.
Later in the evening, if you look to the east, you will find another star pattern associated with boreal winter. While it is a very diminutive group that can barely be seen from the city, it stands out in the sky as you move to darker skies. This group is the Pleiades, also known as the Seven Sisters in our Greco-Roman derived sky lore. Ancient Chinese records dating to some 4500 years ago mention them, and recent work by archaeoastronomers has shown that many Mesoamerican cultures built their ceremonial centers to align with the Pleiades’ rising. Virtually every culture that has left some record of their sky legends mentions the group, and they even appear in the lore of the fabled Middle Earth of J.R.R. Tolkien’s epic tales of hobbits, elves, and magic rings, where they were known as “Remmirath”, the “Netted Stars”. In Japanese they are known as “Subaru”, and you can see a stylized representation of them on every car of that name. They are often associated with the coming of winter in northern climes, and sailors regarded them as portents of gales and fierce seas. Others associate them with agriculture, marking the time to plant when they set just after the Sun in the spring and time to reap when they appear in the fall.
The Pleiades are a true star cluster, located about 440 light-years from Earth. Its brightest members have a dazzling blue tint as seen in a telescope and under very dark conditions it is possible to see the remnants of the clouds that formed them some 100 million years ago. Most of us can see six or seven stars with the unaided eye, but very keen-eyed people can see a dozen. A small telescope will reveal about 80 members, while large telescopes have identified over 1000 stars in the cluster.
Jupiter and Saturn may still be glimpsed in the southwest as evening twilight fades to darkness. They will get a visit from the Moon on the evenings of the 18th and 19th. If you have been watching them for the past few weeks you’ve probably noticed that the gap between them is narrowing; Jupiter is gradually gaining ground on the ringed planet. The gap will continue to close, and in a month we will see the closest appulse of these two planets since the year 1623.
Mars has resumed his eastward motion against the stars, but it will be a few more weeks before this becomes noticeable. He still dominates the sky throughout the evening hours beaming down from among the faint stars of Pisces. Although his disc is now shrinking, a modest telescope on a night of steady seeing will reveal his dusky surface features and small polar ice cap.
You will find Venus in the pre-dawn sky without much difficulty. Her bright glow remains visible right up to the time of sunrise. If you look for her at around 5:30 am you should see her near the bright star Spica as the week begins. She moves rapidly east from the star over the next several mornings.