Sunday, December 1, 2013

Venus Brightly Shining

You may have noticed an unusually bright "star" in the southwestern sky these past few weeks just after sunset.  It is, of course, the planet Venus approaching its brightest aspect of the year in early December.  It's brighter than any of the other stars or planets in our night sky.

Why is Venus so bright?  For one, it's a near neighbor (the next planet in closer to the Sun).  It's also about the same size as the Earth.  And, most importantly, it's shrouded in light-colored clouds which reflect about 75% of the sunlight hitting the planet (Earth reflects only about 30%).

Venus is also only seen in the evening just after sunset or the morning just before sunrise (it alternates over the span of several months).  Why?  Because it's closer to the Sun than we are - the geometry is easier to show with a diagram.

Earth is shown in green.  Keep in mind that if you're on the half of the Earth that faces the Sun it will be daytime and you won't see Venus.  When you're just moving into darkness (on the left side of the Earth in the diagram), you'll see Venus at positions 3-6 as shown (in different phases, just like some of the phases of the Moon).

If you're just coming into dawn (on the right side of the Earth in the diagram), you'll see Venus if it's in positions 7-8 or 1-2 as shown.

If Venus is in the green areas, it won't be seen since it will be lost in the daytime glare of the Sun.

To complicate things, keep in mind that the diagram is just a snapshot.  In reality, both Venus and the Earth are moving in their orbits at different speeds (Venus is moving faster).  Right now, in early December, the situation is as shown below where Venus is approximately in position 5 vis-à-vis the diagram above.

Ever wonder where the name for Venus come from?  Venus, after all, is the name of an ancient goddess of beauty and love.  Most people are familiar with the famous painting by Botticelli shown below.

The Birth of Venus by Sandro Botticelli (1486)

The mythology of Venus, by the way, is a great story.  The Greek poet Hesiod (c. 700 BCE) wrote in the Theogeny the following story about how Chronos lopped off the penis of his father Uranus and tossed it into the sea.  From there was born the goddess Aphrodite (the Greeks earlier name for Venus).

Then the son from his ambush stretched forth his left hand and in his right took the great long sickle with jagged teeth, and swiftly lopped off his own father's members and cast them away to fall behind him...  And so soon as he had cut off the members with flint and cast them from the land into the surging sea, they were swept away over the main a long time: and a white foam spread around them from the immortal flesh, and in it there grew a maiden. First she drew near holy Cythera, and from there, afterwards, she came to sea-girt Cyprus, and came forth an awful and lovely goddess, and grass grew up about her beneath her shapely feet. Her gods and men call Aphrodite, and the foam-born goddess...

Venus was blown to shore on a scallop shell by the god of the winds, Zephyr, who is embracing the breeze Aura shown on the left side of the painting.  Walking ashore, she was recognized as the most beautiful of women and all men desired her as their wife.  She was the goddess of love and feminine beauty.

By the way, here's even more trivia, the pose shown by the goddess here, with her hands covering herself, is referred to in art as the "Venus pudica" where "pudica" is derived from the Latin pudendus which means "which is to be ashamed of" and, of course, the external female genitalia (which is nothing to be ashamed of, but people have always had hang-ups about such things).

The Greek name Aphrodite likely derives from the Greek word ἀφρός (aphrós) for "foam" recalling the circumstances of her watery birth.

The Birth of Venus by William-Adolphe Bouguereau (1879) & the featureless planet
Not too much in common...

So, how did she become associated with the planet?  Even more strangely, the ancient  Akkadians, Assyrians, and Babylonians had a goddess of love and beauty as well whom they called Ishtar.  Guess what?  She also was considered the personification of the planet Venus.

Ishtar (c. 1800 BCE) - British Museum

So, imagine yourself back in ancient Mesopotamia thousands of years ago.  Dark desert skies, no light pollution, and little to do after dark provide excellent conditions for skywatching.  A very bright "star" appears in the evening sky for a few months, disappears, and then appears in the morning sky.  Over and over again.  You know it's special, not like all of the other fixed stars.  With years of observation, you can start to predict its appearances and disappearances.  Why identify this with a beautiful female diety?

Nobody knows for sure.  One speculation that I like is that it simply is beautiful.  Venus is the brightest object in the sky other than the Sun and Moon.  On a clear dark night, it shines brightly and dazzles the eye - much as a strikingly beautiful woman.  Why not?

In any case, pop outside some evening this week around dinner time, gaze to the southwest, and find Venus.  It's unmistakable - nothing else will be as bright.  Feast on her beautiful visage for a few moments before the cold December air forces you back into your warm house.

1 comment:

  1. All of your material is to me a window onto a much wider world of learning. Thankyou !!