For those living in the northern hemisphere, spring is usually considered the wet time of the year,
famous for the April showers that bring May flowers. However, not until fall does the "wet" portion of the starry skies become visible.
For example, during November, constellations associated with water, such as Cetus, Pisces, Aries, and Eridanus, are prominent in the
evening skies.
Above the southeastern horizon is the constellation Cetus the Monster, sometimes known as the Whale.
Perhaps you can imagine Cetus swimming along the river constellation, Eridanus, and resting along its banks. Various cultures have described
Cetus as the whale that swallowed Jonah, or an easy chair leaning back towards Orion. In Greek mythology, Cetus was a monster, while
according to Chinese and East Indians, Cetus is a dragon. Coincidentally, the two myths share the common theme of the rescue of a maiden
from the threats of a monster.
Click here or on the graphic to see a larger animated
graphic showing the constellations; the stars described here; and the constellation patterns as designed by H.A. Rey rather than the classical patterns. Probably the most interesting star within Cetus is Mira, a long-period, pulsating, variable
red giant.
A pulsating star is one that expands and contracts rhythmically.
Scientists theorized that pulsations occur because the red giant star is in the process of running out of hydrogen and is starting to fuse helium
in its core.
Mira has a period that averages 330 days. It is the brightest of the long-period variable stars, and its brightness
also varies the most greatly. Most of the time, Mira is too faint to be seen with the unaided eye; however, its brightness increases from
its minimum to its maximum in 110 days, considerably faster than it dims to its minimum brightness. Having reached its maximum brightness
this past August Mira may now be too faint to see with the naked eye meaning you will have wait nearly another year.
So if you can't wait for Mira to reappear, then look toward the northeast for the star Algol,
the Demon Star. Algol, represents Medusa's head as it is held by the hero Perseus. Algol is an eclipsing binary, variable star in which
a dimmer star orbits a brighter star. From Earth, we see the effects of a partial eclipse of the brighter star when the dimmer star swings
around in front of it and blocks the brighter star. This stellar eclipse lasts approximately ten hours. Algol normally shines as brightly as the stars
of the Big Dipper. However, every 2 days, 20 hours, 48 minutes, and 56 seconds, Algol dims to two fifths its normal brightness.
Click here to
go to the Sky & Telescope web site to use a calculator for finding the dates and times for the minima of Algol.
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