THE SOUTHWORTH PLANETARIUM
70 Falmouth Street Portland,Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
2021-2022: XXIII
"In dreamless sleep, we return to the source: to the life force that animates every living thing. Space collapses, time ceases to exist and we no longer interact with the cosmos as discrete beings. Instead, we mingle with the infinite and experience the eternal as it truly manifests itself, as the absence of temporal flow. In that suspended state no disturbance is possible. We know only the serene breathings of a living Universe that each night bestows on us the rejuvenation of body and the rebirth of spirit."
THE DAILY ASTRONOMER
Monday, October 4, 2021
October 2021 Night Sky Calendar
Part I
A Sky of Simple Shapes
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A format change to our calendar
We will continue to post the night sky calendar in multiple parts.
However, the first part will be an overview of the sky, including information pertaining to constellations and other night sky features.
The second part and any of those subsequent to it, will feature the events listed by day.
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Describing celestial body positions presents a particularly difficult challenge to those who write about it. One must try to communicate locations using degrees, directions and other night sky "landmarks" (a funny term) in the hope that the reader will easily locate a given object or objects. At times, as in early autumn, the task is rendered easier because one should be able to readily find the sky's most prominent features.
First of all, as soon as darkness descends, look straight up. There, in the zenith region, one will find the Summer Triangle.
So named as it remains visible throughout most of the night in the summer, the Summer Triangle is actually easiest to find now. Again, simply look up in the early evening. The three stars comprising it, Deneb, Vega and Altair, seem as though they are adjacent to each other. This apparent proximity is illusory, a result of the way our sky conceals depth. In fact, immense tracts of interstellar space separate them. Altair is approximately 17 light years away. Vega's distance is 26 light years. Deneb, however, is 1000 times more distant: 2,612 light years away. Consequently, when one observes these stars, one is seeing them as they were in the past. Tonight, one sees Altair as it was in 2004. To look onto Vega is to see it as it was in 1995. Deneb appears to us tonight as it was in the 6th century BCE, around the time when Pythagoras of Samoa, the world-renowned mathematician best known for the theorem that still bears his name.*
Dark-sky observers might detect the faintly luminescent band that appears to flow through this triangle. That light is the "Milky Way," an edge on view of our home galaxy. The name is somewhat misleading because every single naked eye star is contained within our home galaxy. However, the "Milky Way" defines the region of highest stellar density: where one finds more stars per unit area than in any other sky region.
Remember as you admire the sky that we're all traveling through the galaxy at 143 miles per second. Our solar system is located approximately 25,000 light years from the nucleus. Like the majority of stars, the Sun is moving along the main disc, part of which we see when we look at the Milky Way band. The stars located far from the band are either located "north," or "south" of the galactic plane.
Just east of the Summer Triangle one will find another simple shape, the Great Square of Pegasus. The square represents the body of Pegasus, the elegant winged horse who was born out of Medusa's blood and eventually tamed by Bellerophon who rode on Pegasus' back when he slew the Chimera. Pegasus is depicted as flying upside down, a reference to Bellerophon's audacious attempt to fly Pegasus up to Olympus. The winged horse prudently refused to ascend to such an exalted height and turned herself over. This sudden inversion caused Bellerophon to plummet to his death after a descent requiring seven days and seven nights.
Just to the north of Pegasus one will find Cassiopeia, a circumpolar constellation resembling the letter "w." A circumpolar constellation is one that doesn't set at our latitude. Cassiopeia represents an ancient Ethiopian queen poised on her throne. Notorious for her appallingly supercilious behaviour, Cassiopeia was hoisted up into the sky as a punishment for she must suffer the indignity of hanging upside down for at least half the night.
The last simple shape, the Big Dipper, begins the night resting on the horizon. Even though it, too, is circumpolar,the Big Dipper might be hidden from view by houses ,trees or other obstructions.
These simple shapes will hopefully help an observer find his/her way around the early evening sky.
Part II of the October 2021 Night Sky calendar tomorrow.
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