February: Venus and Jupiter Dance at Sunset

February 2012

Venus and Jupiter Dance at Sunset

By Calvin L. Chrisman

Venus and Jupiter are putting on a show that will continue into March. The two planets are extremely bright and high in the sky during the early evening and will continue to close on one another as we move into March, eventually passing each other in the middle of the month. Currently, they are hard to miss, about one-third of the way up the sky in the West-Southwest. For a special treat, weather permitting, watch this pair on the evenings of the 23rd to the 26th of February. During this period they will be approached and passed by the waxing crescent Moon. It will be spectacular.

If you want to prove to yourself that these planets are getting closer as the evenings pass, you can measure their progress with your fingers! If you hold your hand out at arm’s length and spread your fingers, they will measure out about 20 degrees of sky. Your closed fist will cover 10 degrees and your thumb 2 degrees. By doing this you can measure the diminishing separation between Venus and Jupiter.

Jupiter, named after the king of the Roman gods, is the largest of the planets. It is over 11 times the diameter of the Earth and over 300 times its mass. Jupiter, like all of the planets beyond Mars, is basically a giant ball of gas while all of the planets from Mars in to Mercury are rocky. The planet rotates on its axis in a little less than 10 hours vs. 24 for our planet. Seen through a telescope, one of the best-known features of Jupiter is its “Giant Red Spot”, which is actually a (very permanent) super hurricane in Jupiter’s atmosphere with winds of up to 400 mph. The Red Spot is four times the size of the Earth and was first seen in 1664.

Many people with telescopes enjoy watching the movement of Jupiter’s largest moons. At present, Jupiter has 66 moons and more continued to be discovered by our exploring satellites. Through a typical amateur telescope, four moons are visible. Galileo, who discovered them, named them the Medicean Stars, after his patrons the Medici’s but they are now known as the Galilean satellites in his honor. The movement of these moons was what made him realize that they orbited Jupiter as it moved through space and was one of the things that led to his support of the Sun-centered theory of the solar system. Several places, including Sky & Telescope magazine and its website, publish tables of their movement. They regularly pass before and behind the planet and cast shadows on Jupiter’s surface which can be seen under good conditions. One of these moons, Europa, is covered with frozen water and may have liquid water below. It is thought to be a possible spot for the discovery of living organisms – no, not little green men, maybe little microbes of unknown colors!


Clear Skies!

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