In late June, you can connect Mars, Saturn and Scorpius’s brightest star Antares to make a nifty right triangle in the southern sky at nightfall. Mars has begun to fade a bit but remains the single brightest “star” in the south direction, its color somewhere between lava and fire. The planet is coming to the end of its retrograde loop, where it appears to stray to the west for a time as our faster planet passes it by. Come June 30th (Thursday) Mars will stop, shift into reverse and resume its normal eastward motion across the sky.
In spring, the Red Planet zipped westward through neighboring Scorpius the scorpion; now in early summer it resides in Libra (LEE-bruh) the scales. Libra is the only constellation in the zodiac that represents an inanimate object. All the others are animals, gods and goddesses or a curious mix of both. In the days of the ancient Greeks, the stars of Libra were considered the claws of the nearby scorpion. These roots are reflected in the Arabic names of its two brightest stars, Zubeneschamali (Zoo-BEN-ess-shah-MAH-lee), the Northern Claw, and Zubenelgenubi (Zoo-BEN-el-jeh-NEW-bee), the Southern Claw.
Later Greeks as well as the Romans knew Libra as the scales of justice held by Virgo the virgin, one constellation to the west. Scales are not only useful for weighing materials but make a nice visual metaphor for “weighing” the different sides of an argument in a dispute.
You may struggle to see a scale with its sample and weight pans here, but the general outline, which resembles a diamond, stands out pretty well even if none of Libra’s stars is particularly bright. The brightest, Zubeneschamali, gleams from the apex of the diamond at magnitude +2.6, a bit fainter than the stars of the Big Dipper.
Its partner in claw-dom, Zubenelgenubi, shines about one fist held at arm’s length to lower right or southwest. At magnitude +2.8 it’s only a tad fainter that the other Zuben. Situated 77 light years from Earth, the light that tunnels from this star into our retinas tonight departed Zubenelgenubi in 1939 at the start of World War II.
Zuben-G appears single to the naked eye, but possesses a fainter 5th magnitude companion about 1/10 of a moon diameter to the northwest or immediately to the upper right of the star. Nearly hidden in the brighter star’s glare, seeing it makes for a challenging test of vision. Give it a try, and if you don’t succeed, any pair of binoculars will easily cleave it.
The sun passes through Libra in November. By that time Mars will be long gone, having chugged three constellations to the east into Capricornus the sea-goat.