Do you remember the Disney song, “When You Wish Upon a Star” from Pinocchio? When most people think of that song, they may imagine the seeing the evening star, the first star that is visible in the evening as the sky gets dark. You can see it in the west tonight or any clear evening for the next several months. Unfortunately, in this day of TV and streetlights, many folks don’t think of stars at all. Old folks, like me, remember “Twinkle, twinkle little star,” or “Star light, star bright, first star I see tonight.” What were we talking about?
First, the “evening star” isn’t a star. It’s the planet Venus. Venus is bright because it can be the closest planet to Earth and its clouds are highly reflective. The ancient Greeks called the evening appearance of the planet Hesperus and the morning appearance Phosphorous. They thought they were seeing two different planets. We now know that we are seeing the planet in the evening sky when it comes around from behind the Sun and races toward us around its orbit. As it passes us heading away, we see it in the predawn sky.
I remember watching Venus for the first time in 1953 with my new homemade telescope. As Venus approached the Earth, it started as a tiny round object low in the west. It slowly changed from to a larger half-moon shape fairly high in the sky. Finally, it became a large thin crescent as it got lower and lower and disappeared into the evening twilight. Then, it passed the Earth and moved into the morning sky. (See the image of Galileo’s drawings of Venus from 1610-13)
I hope you will go outside after dark for the next few months and watch our bright evening star do a slow dance higher and then drift downward. It will be highest in the west by mid-May and look like a half-moon in a small telescope. By August, Venus will be a thin crescent on the horizon right after sunset. You may need binoculars to see it by then. Take time to savor this process. You will end up with a better sense of our cosmic neighborhood. Enjoy!
Back in the 1990s when I used data from a NASA robotic spacecraft named MESSENGER on its mission to Venus. It orbited the planet for several years and used an instrument called a synthetic aperture radar to map the planet’s surface in more detail than ever before. It used radar rather than a regular camera, because Venus’ atmosphere is so dense with sulfuric acid clouds that you can’t see the surface with visible light.
We learned that Venus has a runaway greenhouse effect that makes its surface temperature about 900 degrees. It’s how we first understood “global warming”. The mission gathered so much data that we are still mining the results and discovering new things. Just last week, researchers going through archival images saw the first evidence that Venus has active volcanoes and lava flows. So, studying Venus helps us to understand our own Earth. Amazing.
For questions or comments: James Hill, Mississippi NASA/JPL Solar System Ambassador. jhill6333@gmail.com
