For many of us, the month of August is synonymous with shooting stars. However, planet-lovers won’t be wanting because Mercury, Venus, Mars, Jupiter and Saturn will all be visible to the naked eye at one moment or another during the night.
The mid-August Perseids are perhaps the best known and most widely observed annual meteor shower, and this year looks promising if the weather cooperates: The crescent Moon will set early, so moonlight won’t impede observations. A clear dark sky will reveal the luminous trails caused by interplanetary dust particles entering the atmosphere at high speed. These particles are spread along the orbit of comet Swift-Tuttle, which bears the name of its discoverers — Lewis Swift and Horace Tuttle — who first observed it in 1862. The comet orbits the Sun every 130 years, replenishing the particle stream on a regular basis.
The best time to view the Perseids is just before dawn, on the nights of August 11 and 12. There’s an online App that estimates the number of meteors visible per hour, based on the observer’s geographical location and sky quality. For example, under light-polluted city skies, one can expect to see less than a dozen shooting stars an hour; but in the country, under a pristine sky, over sixty meteors per hour should be visible! Perhaps there’s still time to alter your vacation plans accordingly…
The Moon and planets from dusk to midnight…
Venus shines as the Evening Star this summer and can be seen low on the western horizon at twilight: It sets an hour-and-a-half after the Sun. At the beginning of the month, Venus occupies the constellation of Leo; on August 9, a thin lunar crescent, just three days old, will appear near the dazzling planet. Venus enters Virgo on the 11th and as the evenings progress it gradually approaches the bright star, Spica, whose name describes a stalk of wheat held in the maiden’s hand.
Saturn is visible in the southwest at the end of twilight: It’s to the left of the star, Spica, and slightly brighter. Note how the gap between Saturn and Spica slowly diminishes as August advances. At month’s end, the ringed planet sets less than two-and-a-half hours after the Sun.
Over the course of four consecutive evenings — from August 10 to 13 — the crescent Moon will leap-frog past Venus, Spica and Saturn. On August 10, half-an-hour after sunset, the Moon will appear to the left of Venus; the following evening, the lunar crescent will be to the lower right of Spica; and on the 12th, it will be mid-way between Spica (to the lower right) and Saturn (above and to the left). And finally, on the 13th, the Moon will be to the left of the ringed planet.
On August 15, the first quarter Moon will stop next to the star, Antares, in Scorpius, and over the following two evenings it will pass above the constellation of Sagittarius.
…and before dawn
Mercury, Mars and Jupiter can be seen shining in the morning sky among the stars of Gemini as the month begins. Mars rivals the twin stars, Pollux and Castor, but Jupiter outshines them all. Jupiter, Mars and the waning lunar crescent will form a brilliant celestial trio on the mornings of August 3 and 4 — a sight not to be missed!
Mars moves rapidly among the stars throughout the month: the Red Planet crosses the border of Gemini and Cancer on August 25, and forms a nearly vertical line with Pollux and Castor above.
Mercury is visible at dawn until mid-month: Look for it above the eastern horizon about half-an-hour before sunrise. The tiny planet precedes the Sun until the 24th, when their roles become reversed: Mercury will then pass behind our daytime star and enter the evening sky, where it will follow the setting Sun until October.
The Summer Triangle is directly overhead around midnight. It consists of three bright stars in three different constellations: Deneb in Cygnus, Vega in Lyra and Altair in Aquila. Below Altair, near the southern horizon, there’s group of stars in the shape of a teapot: It’s part of the constellation of Sagittarius, superimposed against the bright center of the Milky Way. In fact, the Milky Way, which stretches from south to north, gives one the impression of steam escaping from the teapot’s spout. This region of sky is particularly rich in nebulae and star clusters. Some of these deep-sky objects are visible in binoculars, such as the Lagoon nebula (M8), the Omega nebula (M17), the Sagittarius cluster (M22) and the open cluster M25. Sagittarius, the archer, aims his arrow toward Antares — a red supergiant star ten thousand times more luminous than the Sun — at the heart of Scorpius. The scorpion is one of the few constellations that actually looks like the creature it represents.
Clear skies !