Venus, Burning Like a Silver Flame

Venus, the second planet from the Sun, is a dazzling sight in the southwest after sunset. Burning like a silver flame, it outshines all the stars in the night sky as well as all the planets in the Solar System. One reason it is so bright is that it is relatively close to us, though its distance from Earth varies greatly. Its brilliance is mainly due to its thick atmosphere, whose clouds reflect about two-thirds of the sunlight that hits it.

Venus orbits the Sun just inside the Earth. Because of this, Venus always rises and sets within a few hours of sunrise or sunset. Indeed, ancient civilizations identified it as the Morning Star and the Evening Star, not realizing that both were the same object. It’s currently in its Evening Star appearance, and will remain visible from now until May when it disappears again into light of the setting sun.

Imagine Venus in its orbit directly behind the sun. At this point, it would rise and set with the sun. We would not be able to see it, as Venus is lost in the daylight. Venus orbits the Sun faster than we do, however, and gradually it starts to catch up with us in our orbit. As it does so, it moves out from behind the sun so that it remains visible after the sun sets—thus, the Evening Star. Finally, Venus catches up with us in our orbit, and at that point it lies directly between Earth and the Sun where it cannot be seen. After it passes us, it eventually moves far enough away from the sun that it rises before the sun does—thus, the Morning Star.

It stays in the morning sky until it returns to the point where we started, directly behind the sun. It takes about 580 days for Venus to complete this cycle, spending 290 days in the evening sky and 290 days in the morning sky. Of course, we can’t see it until it moves far enough away from the sun to escape the twilight. The 580 day cycle was known to early civilizations, particularly the Maya whose religious calendar was partly based on the regular appearances of Venus.

Although Venus looks beautiful in the night sky, it is truly an alien world. Its atmosphere, which makes it so bright in our sky, is so thick that the pressure on its surface is about what the pressure is at a depth of 3300 feet in Earth’s oceans. Not only would we be crushed, we would also melt, as the average surface temperature is above 800 degrees Fahrenheit due to a runaway greenhouse effect. The Soviet Union sent a number of spacecraft to the surface of Venus in the 1970’s and 80’s. They returned valuable data to Earth, but none of them lasted more than a few hours. In the early 1990’s, the Magellan spacecraft used radar to penetrate the atmosphere and map 98% of the surface of Venus.

Another Venusian oddity is that it rotates on its axis backwards, and more slowly than any other planet in the Solar System. If you were on the surface of Venus, the sun would rise in the west and set in the east. But you would also have to wait a long time, as it is about 60 Earth days from sunrise to sunset.

When the clouds part here on Earth, you can get a good view of Venus as soon as the sun sets. These days in Chicago, Venus sets around 9 pm CST, but as winter turns to spring, the dazzling second planet from the sun will set later and later.


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