Venus reappears
That brilliant “star” very low in the southwest in evening twilight is Venus. You’ll need a clean western horizon to see it. You’ll probably need binoculars to see the elusive planet Mercury just below it.
As the brightest object in the nighttime sky besides the moon, the sun’s second planet is hard to miss. If it’s cloudy tonight, take heart. Venus will be visible through the end of winter. As the days and weeks pass, it will be a bit higher every night.
Watch it slowly migrate to the west along the horizon. The ancient Greeks were at first a bit confused about the planet. Because Venus is closer to the sun than Earth, it always appears close to the sun and is thus visible only in the evening just after the sun has set or in the morning just before sunrise. Because it appeared sometimes in the morning and sometimes in the evening, the early Greeks thought it was two objects — Hesperus, the evening star, and Phosphorus, the morning star.
This time around, it’s the evening star. The Romans identified Venus as the goddess of love and beauty, and it’s easy to see why. Few objects in the sky look so beautiful. My daughter, who is a Latin scholar at SUNY Buffalo, reminds me that the Roman goddess — and hence the planet —was sometimes called Hesper, or Vesper, which means evening. A holdover of that meaning can be found in the Catholic celebration of Vespers, or evening prayers.
Astronomers used to think that Venus was Earth’s twin sister. At about 8,000 miles wide, the planet is about the same size as Earth. At 67 million miles from the sun, it’s only 25 million miles closer than our planet.
However, despite the similarities, we’ll find no life on Venus. Venus turns out to be Earth’s evil twin. The problem is its atmosphere, which is mostly a very thick layer of carbon dioxide covered over completely with sulfuric-acid clouds. The air pressure is so great that an unwary astronaut who landed there would be crushed flat like a bug under a heavy atmospheric boot.
The clouds let in only about 2 percent of the sun’s light, which suggests that Venus should be cold, despite its proximity to the sun. The trouble is that the dense atmosphere is very efficient at trapping the heat from the sun’s feeble rays.
On Venus we find an out-of-control greenhouse effect with temperatures of 900 degrees Fahrenheit everywhere on its surface. You wouldn’t want to visit a planet where sulfur lies in molten, steaming pools on the ground. The weirdness doesn’t end there. Venus has the slowest rate of rotation in the solar system. Our planet turns once on its axis every 24 hours. Venus rotates once every 5,832 hours, or once every 232 Earth days. A Venus year — the time it takes to make one revolution around the sun — is only 225 days long. A Venus day is thus seven Earth days longer than its year!
Daytime on Earth begins as the sun rises in the east and ends when it sets in the west, a phenomenon caused by the Earth’s west-to-east rotation. Venus rotates in the opposite direction, i.e., from east to west. On Venus, the sun rises in the west and sets in the east.
The mythical inhabitants of Venus would think it perfectly natural to see the sun rising in the west. They would have a harder time with the high temperatures and atmospheric pressure. The gentle sulfuric-acid rain would be a major inconvenience.
But the worst thing about living on Venus would be the clouds. Imagine the sun as a feeble red orb, Earth and all the planets blocked by the unvarying cloud cover. Imagine a sky without the beautiful constellations or the galaxies of stars. Imagine a civilization with no sense at all of the vast universe that surrounds it, its imagination limited to the paltry confines of its tiny planet.
We’ll find no life at all on Venus. Thank goodness for that.
Tom Burns is director of Ohio Wesleyan University’s Perkins Observatory in Delaware, Ohio. He can be reached at tlburns@owu.edu.
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