The backyard astronomer: Lovely Venus, where it rains battery acid and a pizza would cook outside in nine seconds
Throughout history, keen skywatchers would follow the weekly and monthly movement of bright objects against the background sky. The early Greeks referred to the planets of our solar system as the “wanderers”, and there are five that can be seen and followed with the unaided eye.
The planet Venus is now seen high in the western sky shortly after sunset. Other than the moon, Venus is the brightest nighttime object—and for good reason. It is completely surrounded by thick clouds comprised of carbon dioxide and reflects about 75 percent of sunlight that falls on them.
On a moonless night out in the dark countryside and away from any light source, this beacon will cast a shadow on a sheet of white paper. It can also be a great subject for astrophotography.
However, what goes on under the clouds is something out of a science-fiction novel. Thanks to its 50- to 75-kilometre cloud deck, pressures at the surface are 90 times that of Earth. That is comparable to being a kilometre under the ocean, or in a car crusher. It rains sulphuric acid (battery acid) that never reaches the ground.
The clouds also produce the greenhouse effect, trapping the solar energy and locking it in. This keeps the day and night side a toasty 400° C, which is hot enough to cook a large pizza in nine seconds. It is safe to say that human astronauts will never visit the Venusian surface.
However, in 1970 the Russians launched the Venera 7 probe, which became the first spacecraft of its kind to land on another planet. The craft only lasted about 50 minutes, but it opened the door to the planet’s hidden secrets. Today, X-ray images pierce the Venusian clouds to reveal its landscape and volcanoes that still seem to be erupting.
Venus and Mercury are termed inferior planets, as they reside inside Earth’s orbit. It takes only 224 days for Venus to circle the sun, and the planet takes on different phases when viewed through a telescope, much like what we see with the moon as more or less sunlight illuminates its surface.
On March 1, Venus will only be illuminated 62 percent. It reaches its farthest point from the sun on March 24, then begins to move lower to the horizon.
Over the next few weeks, the planet will position itself between the sun and Earth. If you follow this progression through a telescope, you will notice the planet growing in size as it moves closer to us but shrinking in illumination. On April 3, it will appear to be located in the Pleiades Cluster, and on the night of May 21-22, it will team up with Mercury low in the northwest sky but will be a thin four-percent lit crescent.