Ares & Anti-Ares in the Summer Sky

When hiking the mountains and meadows of summertime Montana, it's always good to watch your step'lest you encounter the occasional bison or moose patty or one of the rodents, snakes, lizards, or other creepy-crawlies that inhabit the various terrains of the region. The terrain of the sky offers reminders of this by providing its own creepy-crawlies to discover.

The sky's only arachnid is Scorpius, the scorpion, its fishhook-shaped outline of stars shuffling along the southern horizon this season. Nearly stepping on it is Ophiuchus the serpent-bearer, almost knocking heads with the upside-down Hercules as he grips the wriggly snake Serpens, the head (Caput) to the west, the tail (Cauda) to the east. Above circle birds waiting for scraps when the tussle is over: Aquila the eagle, the vegetarian Cygnus the swan, and Lyra—ostensibly the Greek lyre, but seen by some as a vulture in the sky.

The beating heart of the scorpion is marked by the bright star Antares, a red supergiant some 600 light years distant. Its name means "rival of Ares," referring to the Greek god of war—the Roman Mars. The rivalry is thus made clear in the competing red colors of the star and the planet Mars, which follows behind several constellations to the east of Antares this summer.

Mars had a sinister reputation of its own as an agent of strife. Its associated god was popular in ancient Rome as the purported father of the city's founders, but it was known to the Babylonians as Nergal and was linked to war, pestilence, and the dead. And no one overlooked that it was the color of blood.

The ruddy planet will be bright and well-placed for viewing this summer, for this is the every-other-year when the speedier Earth catches up and passes (that is, laps) the slower Mars in their respective orbits around the sun. Mars will rise in the east around midnight in late June, and by about 10 p.m. in late July. On August 28, as the Earth slips between Mars and the sun, the Red Planet will appear opposite the sun in the sky, rising at sunset and visible all night. (Thereafter it will already be up in the east at nightfall.) This is the time when Mars lies closest to us, and thus appears brightest in the sky.

In fact, the slowly changing eccentricities (out-of-roundedness) of the two planets' orbits have conspired to place Mars ever so slightly closer to us in late August (at a little under 35 million miles) than it has been in some 60,000 years—or will be again until the year 2287. Look for the planet well to the east of Scorpius, past the fantastical Sagittarius the centaur archer and Capricornus the sea goat, and you'll find it bathing in the starry stream of water from the urn of Aquarius the water-bearer. Its brilliance and hue will render it unmistakable. And in brightness, at least, Antares will be no rival this summer, for Mars will shine 36 times brighter than the star.

There are no tales of rivalry between the god of war and the scorpion, but Scorpius and Orion are another matter. The Greeks say that when the boastful hunter claimed that he could kill just about any of Earth's creatures, the Earth-goddess Gaia sent a sneaky Scorpius to creep up to Orion, sting him fatally on the foot, and prove him wrong. And so Scorpius did, but became a victim of collateral damage when the large and stricken Orion fell upon the scorpion and squashed it flat.

The gods then placed the foes in opposite parts of the heavens to avoid further unpleasantness. And so the summer sky belongs to Scorpius. But when it scuttles out of sight into the west, look for wintry Orion to stride over the eastern horizon—watching his step as he comes.

The Taylor Planetarium offers guided tours of the universe daily at the Museum of the Rockies, 600 Kagy Blvd., 994-2251.