On Astronomy — A parade of planets

Published 12:22 pm Saturday, October 9, 2021

As fall approaches and we have clearer skies, perhaps you’ve noticed a bright star in the East and a bright star in the West at sunset. Well, they’re not stars but planets. In the East is the giant planet Jupiter, and a little to the right is the dimmer, ringed planet Saturn. As the evening progresses, Jupiter and Saturn rise higher in the sky, while in the West, the bright goddess of love and beauty, Venus, is setting. Between the planets are the constellations Sagittarius, the teapot, and Scorpius, the scorpion. The band of planets and the easily recognized teapot and scorpion are a stunning sight. For you early risers, later in the month, Mercury makes an appearance as the morning star.

Jupiter is the fifth planet from the Sun and by far the largest. It is a swirling ball of toxic gases. The giant red spot is an anticyclonic storm with winds up to 268 mph. It can be seen in small amateur telescopes and has been observed for hundreds of years. Galileo’s observation of four moons circling the planet was one of the final nails in the coffin of the idea that the Earth was the center of the universe, that everything circled the Earth. The four Galilean moons are barely glimpsed with 10X50 binoculars and are easy to see in small telescopes. The Galilean moons are so bright you could observe them with your naked eyes were it not for the glare of bright Jupiter.

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Saturn to the right of Jupiter is dimmer and slightly reddish. The ringed planet is the sixth from the Sun and the second largest. The rings are composed primarily of chunks of water ice. Some scientists speculate that the pressure and composition of Saturn’s atmosphere cause diamonds to fall like hail in the atmosphere.

Venus, beautiful Venus, is the third brightest object in the sky, outshined only by the Moon and the Sun. Under ideal conditions, you can observe Venus in daylight. To try, start when Venus is a morning star, and follow it carefully as the dawn brightens. While it is a beautiful sight, Venus is no place to picnic. The atmosphere is primarily carbon dioxide, and the average surface temperature is 867 degrees Fahrenheit. There is sulfuric acid in the atmosphere, and its pressure is 92 times that of the Earth.

Mercury is the first planet from the Sun. The term planet is from ancient Greek for “wanderers” as they moved against the background of fixed stars. Mercury moves quickly and is named for the Roman fleet-footed messenger of the gods. Have you ever seen Mercury? It’s relatively easy if you know where and when to look. Mercury is well-positioned for observation as the morning star from October 21 to 27. Look low to the horizon to the East just before daylight. Mercury rises higher as dawn breaks but it’s soon lost as the day brightens.

Mars appears too close to the Sun for easy observation. However, the October parade of planets is your chance to enjoy four of the five bright planets.