THE SOUTHWORTH PLANETARIUM
207-780-4249       www.usm.maine.edu/planet
70 Falmouth Street  Portland, Maine 04103
43.6667° N                   70.2667° W
Founded January 1970

THE DAILY ASTRONOMER
Tuesday, July 7, 2016
Bye, Bye Bees!

In winter and early spring, one can observe both of our sky's prominent galactic star clusters, the Pleiades (Seven Sisters) and Praesepe (the Beehive) in the evening sky.  They resemble diffuse light patches located at either side of the Milky Way's diffuse light bridge.  In fact, they look like fragments that flaked off the galaxy b and.    Unlike the much larger globular clusters lurking around the galactic halo, these open systems travel around the Milky Way's spiral arms with us.   Consequently, these open clusters tend to be more prominent owing to our closer proximity to them.    The mammoth globulars, confined to the galaxy's center, are far more distant and therefore much more difficult to see.


Beehive Star Cluster:  a galactic cluster in Cancer the Crab has vanished into the dusk, destined
to return to the pre-dawn early autumn sky.   Image:  Michael Sherick
​
We have no difficulty observing the Seven Sisters and the Beehive in the winter and spring as they are quite distinctive objects within the star fields.  They are particularly beautiful when observed telescopically, as such observations permit us to resolve many more stars: hundreds more, provided the telescope is sufficiently powerful.       Even without a telescope, one can still behold lovely clusters, the collective light of which produces a phantom-like glow in the sky.

In May, we lose the seven sisters for awhile as the Sun obscures our view.   Throughout the rest of May and June, we can still watch the Beehive Star Cluster drawing closer to the setting Sun.  In July, Prasepe sets soon after dark and by mid month we lose it altogether.    On August 1, the Sun is directly over the Beehive, itself.      By September, it slowly emerges in the pre-dawn eastern sky, where one will currently find the Seven Sisters.

This week, we prepare to bid adieu to the Beehive Star Cluster, so named as they resemble a bee swarm when seen through a telescope.     Their passage out of the evening sky marks the arrival of middle Summer.*  Their return to the morning heralds the return of earliest autumn.     While we're still protected from autumn for the moment, we at least know that summer's progressing along nicely.   The Beehive's imminent disappearance serves as a handy reminder that the natural cycles continued unabated.

For some, that is quite a comfort.





*"Middle summer" is not the same as Mid-summer, as the former term applies to the middle of summer, while the latter term "mid summer" means summer's beginning (solstice.)