From the USM Southworth Planetarium
“Keeping a watchful eye on a complex sky”
THE DAILY ASTRONOMER
July 28, 2009
Pre-dawn Pleiades
After a decade-long hiatus, the sultry weather has finally arrived here in the place where dampness and frigidity are manufactured and shipped to all parts of the world.
We realize that this announcement is of little interest to those spoiled subscribers basking in the perpetual heat of the desert southwest. However, we here in the rain-swept world are giddy with glee over today’s hot, humid and hazy forecast. (Thanks, Roger.)
To commemorate the summer heat’s return, we focus now on a winter pattern that has emerged in the pre-dawn eastern sky. The Pleiades, otherwise known as the Seven Sisters, dissolves into invisibility by May, when the Sun moves from Aries into Taurus.
The star cluster rests on the Bull’s shoulder and is considered a part of the Taurus constellation. It returns to the pre-dawn sky in July: the first of the many stellar sights that adorn our winter evening sky.
One of the many mythological stories pertaining to these sisters involves Orion, which is still obscured by the Sun. Orion is depicted as pursuing these seven sisters in amorous earnest across the sky. All of these maidens are afflicted with what most men consider a double-curse: enchanting beauty coupled with discerning standards.
Upon seeing this massive and rather uncouth hunter in rapid pursuit, they fled hastily away and have managed to maintain a pious distance from their lustful suitor. Protecting the Pleiades is Taurus the Bull who is pressed horn to shield against Orion and prepared to engage the latter in mortal combat.
Astronomically, the Pleiades is one of the closest galactic star clusters. Also known as open clusters, galactic star clusters are smaller, younger and contain fewer stars than Globulars, the other type of star cluster.
The Pleiades is 440 light years away and contains about 200 stars. Of these, only six or seven are resolvable with the unaided eye. It is for this reason that the cluster is called the “Seven Sisters.”
When one sees the eastern horizon tinctured by the first hints of twilight, one shall also see these sisters rising into the eastern sky. Even though we’re about to enter the hottest -let’s hope- part of Summer, the winter sky stars are starting to enter stage left, as they always do this time of year.
