Science. Education. Community. Fun.

Looking Up

Looking Up This Month
August means the Perseid Meteor Shower. Each year in Au-gust, the Earth plows through the stream of dust left by Comet Swift-Tuttle, first seen in 1862. Swift-Tuttle takes 133 years to make a trip around the Sun. Comets are like Hansel & Gretel, dropping breadcrumbs in the forest. Instead of breadcrumbs, comets shed dust particles roughly the size of a pencil eraser. When they enter the atmosphere at roughly 130,000 mph, they slow down in the air, just like tossing a small stone into a water-filled aquarium. At about 50 miles above the Earth, they ion-ized the air and the result is a glowing streak in our sky. The path of the meteors are all parallel but, from our line-of-site, they appear to be coming from a spot near the constellation Perseus. On a good, dark night, during the morning hours, one might see an average of one meteor per mi-nute. This year, the view will be hampered by a bright Moon as the peak occurs only about three days ahead of a full Moon. Though the max is predicted to be the evening of the 12th and the morning of the 13th, it might be wise to start looking the week-end just prior to these dates and look in the pre-dawn hours when the Moon has either set or will at least be low in the west. Report what you see!
But there are other things to see in the sky this month. On paper, we lose Mars this month and gain both Venus and Mercury. Two of the three planets will be extremely low this month and, for the most part, unobservable. Mars passes behind the Sun (from our point of view) at the end of the month. Venus also passes behind the Sun, though going in the opposite direction, on August 6. Given the angle between the orbit of Venus and the western horizon is very small, Venus will set just after the Sun for most of the month. It may not be until almost October before we start eas-ily seeing it in the southwest.
Mercury probably has its best morning view this month. Great-est separation from the Sun (about two fists held at arm’s length) occurs on August 10. On that morning, Mercury rises just after 4:30am, just north of east (see the image). Be careful, though, as, just above the planet, are the stars Castor & Pollux. In fact, the two stars of Gemini point down to Mercury. By the morning of the 17th, Mercury is rising to the left of the bright star Procyon and rising at 5am. Mercury also come out from the Sun’s glare in the evening sky right at the end of August, but this is not a great show-ing for Mercury. At its highest, Mercury still only sets about 40 minutes after the Sun.
Of course, we haven’t mentioned Jupiter and Saturn yet! Both are show planets this month, roughly sitting due south as the Sun sets. In fact, Jupiter transits the meridian in the evening twilight. Jupiter is above and left of the red star Antares. The Moon is near Jupi-ter on August 9 and to the right of Saturn two days later.