THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W 
Altitude:  10 feet below sea level
Founded January 1970
Julian date: 2458764.5
2019-2020:  XXVII
            "By the pricking of my thumbs, 
                     Something wicked this way comes."
                                   -2nd MacBeth witch


THE DAILY ASTRONOMER
Wednesday, October 9, 2019
October Night Sky Tour Part I


Up Next at USM Theatre
The Women Who Mapped the Stars
by Joyce Van Dyke
Oct. 4-13th, 2019
For more info: usm.maine.edu/theatre

We begin with an ardent apology.
As much as we love our subterranean hobbit hole star dome theatre, it doesn't do the real night sky justice.    The actual sky, the panoramic portal onto our own little galactic niche, is certainly bigger to the point of being unbounded.  Yet, it also bristles with ceaseless energy, is envlivenened by vibrant color, bears the imprint of the ancient and immortal, and every incandescent stellar pinpoint is like a luminescent window along an expansive urban skyline:  the remote light of another realm displaced from our own, but still part of an unfathomably larger system.


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Venture outside tonight at 8:00 p.m.   Directly overhead and looming high and bright is Cygnus the Swan, more popularly known as the "Northern Cross."  Ironically, more people have heard of the Southern Cross, a famous star pattern that only observers south of the 30th north parallel can see.      Here in the mid latitudes, the Northern Cross is perfectly placed this evening.  Even the casual observer, or the sour-souled curmudgeon who steps outside at the insistence of his exasperatingly persistent grandchildren, will experience no difficulty finding the cross early this evening. Just look up toward the zenith and there it shall be.

Like the other constellations, the Northern Cross has retained its shape over thousands of years despite the rapid motion of its component stars.   Although these stars speed through the galaxy at more than 100 miles per second, their apparent positions change imperceptibly over a human lifetime and by minute amounts over the centuries because they are so distant.   If only we had lifespans extending tens or hundreds of thousands of years would we ultimately observe the distortions and eventually disassociations of the constellations as a consequence of these motions.

How far?  Light years away!
We toss around that term quite often.  A "light year" is the distance that light travels in one Earth year when moving through a vacuum at the speed of 186,290 miles per second: about 5.8 trillion light years.   Deneb, the brightest star in Cygnus, is about 2615 light years away.   We're seeing that star tonight as it actually appeared around the time that Nebuchadnezzar II was building the Hanging Gardens of Babylon.    Our portal permits observations of distant space and remote times.

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A bit closer to home is Venus, that dazzlingly bright planet one can now see in the western early evening sky.     On viewing this gorgeous world, we can well understand why Venus was named for the Roman goddess of love and beauty, the counterpart to the Greek Aphrodite.    One would hardly find it beautiful and lovely were one to venture down onto its surface which roasts at 900 degrees Fahrenheit.  The suffocatingly thick carbon dioxide atmosphere traps the Sun's intense heat, producing the hell furnace conditions from pole to pole.  

Wow!
Yes, not that you're looking toward the east where we pointed, you can't see anything in particular, apart from the star-adorned firmament.  We just saw a flicker of light: an early Orionid meteor appearing to travel from the east.    The problem with meteors is that by the time a companion observes one and alerts you, it's gone,   Meteors are the rapid lights generated by descending meteoroids that burn out more than 50 miles above Earth's surface.  The infiltration of these particles excites the nearby atoms which elevates their electrons into higher energy states.  When the electrons settle back down to their original states, they release the photons we see as meteors.   These meteoroids are fragments of Halley's Comet, currently trudging slowly along the outer part of its orbit.  It is destined to turn around in December 2023 for a 2061 excursion through the inner solar system.

Part II tomorrow.


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