In the minds of vacationers, the most anticipated astronomical event is without doubt the Perseid meteor shower, which returns faithfully each year and almost always offers an interesting show. As a bonus this August 2016, all the naked-eye planets are visible in the twilight: a unique opportunity to get to know Mercury, Venus, Mars, Jupiter and Saturn.
The Perseids
Every year around mid-August, the Earth passes near the orbit of periodic comet Swift-Tuttle. Dust particles, liberated by the comet, affect Earth’s upper atmosphere giving rise to the best known of meteor showers—the Perseids.
In 2016, maximum activity of the Perseids is predicted for the morning of August 12. The pre-dawn hours of the night of August 11 to 12 will be best for observing the event. Moreover, the Moon will set shortly after midnight; and Perseus, the constellation from which the meteors appear to emanate, will be high in the sky. Find an observing site far from light pollution, dress warmly, and enjoy the shooting stars: under a very dark sky, over fifty should be visible per hour!
If the weather is less than ideal on the night of August 11 to 12, it’s good to know that the Perseids can be observed—albeit in less numbers—on the nights that precede and follow the maximum.
And here’s an interesting aside… Algol, one of the brightest stars in Perseus, is actually an eclipsing binary system: two stars that orbit one another, whose orbital plane is oriented edge-on toward Earth, which causes the stars to eclipse each other at regular intervals. Algol reaches minimum brightness every 2.87 days: During an eclipse, the total luminosity of the binary system fades visibly for a ten-hour period. One such minimum will occur on August 12 at 9:34 p.m. EDT, and you can to watch it gradually return to full brightness over the following five hours.
Planets on the menu
This month, you’ll also be able to see all of the naked-eye planets. The first group of planets can be found with a little effort, low on the western horizon just after sunset: Binoculars will help you spot Venus, Jupiter and Mercury, in decreasing order of brightness. On the evenings of August 5 and 6, a thin crescent moon will frame Jupiter. Later, on the evenings of August 26 and 27, Venus and Jupiter will be extraordinarily close to one another, so that to the naked eye they’ll seem to merge, offering a great opportunity for magnificent landscape photos.
A second group of planets, a duo composed of Mars and Saturn, will be visible in the twilight above the west-southwest horizon. On the evening of August 11, the gibbous moon will form a large equilateral triangle together with the two planets. Notice Mars’ rapid movement toward the left with respect to the background stars: from evening to evening, the Red Planet approaches Saturn and the red supergiant star Antares, in Scorpius. From August 22 to 25, Mars will be less than 2 degrees north of Antares, passing directly between the red supergiant and ringed planet on the 23rd and 24th.
Had your fill of planets? Then enjoy the Summer Triangle, which is easy to locate, immediately overhead near the zenith. The beautiful constellations of Cygnus, Lyra and Aquila extend a warm invitation to discover the starry universe.
Clear skies!
