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
Julian date: 2457669.16
"The happiest place on planet Earth."
*THE DAILY ASTRONOMER*
*Thursday, October 6, 2016*
*Fox and Arrow*
Envisioning the characters around the constellations is not a task for the
faint-hearted. Most star patterns do not truly resemble whatever creature
or object they are meant o represent. (The adversarial constellations
Orion and Scorpius are notable exceptions.) For this reason, we often
encourage sky watchers to seek out shapes and other prominent patterns
before they begin to imagine the constellation figures associated with
those shapes.
Today, we're going to point out two small constellations and will
understand if you decide not to bother with the imagination part. These
constellations, called Vulpecula the Fox and Sagitta the Arrow, are
literally tucked away inside the Summer Triangle. Since this triangle is
high overhead in the early evening, one could consider early autumn as the
best season to find them. Then again, they are so difficult to see even
during the best season.
*Vulpecula and Sagitta: The Fox and the Arrow.*
*Two constellations hidden within the Summer Triangle. Whereas Sagitta
dates back to at least the Greco-Roman era, Vulpecula is of more recent
vintage, having been first created by Johannes Hevelius (1611-1687) One
can find them tonight high in the evening sky. Or, more correctly, one can
attempt to find them tonight high in the evening sky.*
Just south of Cygnus the Swan, Vulpecula the Fox consists of a few stars in
a crooked line arrangement. Created by acclaimed seventeenth century
astronomer/Uranographer Johannes Hevelius (1611-1687), Vulpecula was
originally depicted with a goose in his jaw, and so was known as "Vulpecula
cum Anser," (Fox with Goose.) Even though the goose eventually
vanished, the constellations brightest star is named "Anserine," the goose
star.
Look out of the fox to find the small constellation Sagitta. While it is
as inconspicuous as Vulpecula, Sagitta is a much older constellation. Its
origin extends back to the Greco-Roman era. Mythologically, Sagitta
represents the arrow that Hercules used on Aquila, the Eagle who gnawed
Prometheus' liver. Prometheus, the best ally humans ever ignored, brought
fire to the mortals, much to Zeus' chagrin. Zeus punished Prometheus in a
rather clever and cruel manner. Prometheus was chained to a rock and
condemned to have an eagle gnaw at his liver from dawn to dusk. At night
the liver regrew, only to be devoured by the same eagle the following day.
This continued for many years. Had Hercules not eventually intervened by
slaying the eagle and releasing Prometheus, this constant
feast-regeneration-feast-regeneration would still be happening today.
The arrow Sagitta rests just above the eagle which was slain by it.
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FROM THE CATACOMBS OF INFINITE KNOWLEDGE
*"M27: The Dumbbell Nebula"*
*M27: "The Dumbbell Nebula" A planetary nebula in the constellation
Vulpecula the Fox. This nebula is approximately 1,360 light years from
Earth. It formed after a star cast off its outer layers, leaving only a
white dwarf behind. Image: ESO*
Our Messier tour continues (and we know we're lagging behind a bit.)
Today's DA took us to the constellation Vulpecula the Fox. While we're
here, anyway, we should take a moment to admire the beautiful Dumbbell
Nebula, a planetary nebula that Charles Messier, himself, discovered in
1764. In fact, this object was the first planetary nebula Messier
discovered. A planetary nebula forms when a a star that is less than
eight times more massive than the Sun ends its life cycle. It casts off
its outer layers, leaving only a white dwarf core behind. These objects
were called planetary nebulae because they resemble planets when observed
telescopically.
The Dumbbell Nebula is about 1,360 light years away. By analyzing the
expansion rate of the nebula's outer layers, astronomers estimate that the
its progenitor star perished between 11,000 - 13,000 years ago.
Eventually, this nebula will dissipate into invisibility and its
constituent material will enrich the gases within its proximity.
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*Tucked away in an alcove within the catacombs of infinite knowledge*
The central white dwarf star within the Dumbbell Nebula has a radius 5.5%
that of the Sun's, making it one of the largest white dwarf stars known
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*On piece of neglected papyrus within the catacombs*
The Sun will end its life as a planetary nebula is about
6.5 billion years.
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