A Permanent Super Hurricane
By Calvin L. Chrisman
August offers two terrific sights; the planet Jupiter is bright and visible most of the night and the Perseids meteor shower peaks in the middle of the month. 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 to the Sun are rocky. The planet rotates on its axis in a little less than 10 hours vs. 24 for our planet. It can be seen in the southern sky near the teapot of Sagittarius and shines at a bright magnitude -2.6.
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. It is four times the size of the Earth and was first seen in 1664. In recent years, another large storm, formally known as Oval BA and informally as “Red Spot Junior”, has appeared on the planet. In late 2006 Junior passed very close to the Giant Red Spot and observers watched closely to see if it would be absorbed. It survived the encounter and these two will come close again this year.
Many people with telescopes enjoy watching the movement of Jupiter’s largest moons. At present, Jupiter has 63 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 and 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 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!
The annual Perseids meteor shower will be active starting in early August and will peak early on the morning of August 12. They will be most visible after midnight during the month when the planet is facing most directly into the on-coming meteors. On the morning of the 12th, all but the brightest meteors will be blocked by moonlight until about 1:00 a.m. DST. After that, assuming clear skies, you should be able to spot a meteor every minute or two. You do not need to look toward the constellation Perseus, as the meteors will be visible across the entire sky. Their tails will point back toward Perseus. Just find an area of visible sky and settle back to watch. If you have ever wondered, a meteor is what you see crossing the sky. If it survives a trip through the atmosphere and makes it to the Earth, it is then referred to as a meteorite. The light trail that you see is not the space rock burning up; it is a trail of ionized gases caused by the shock wave of the rock passing into the atmosphere at high speed.