The brightening Moon now sits to the left of Spica tonight, helping guide the way to Libra’s lovely double star, Zubenelgenubi.
The waxing Moon has now moved to the left of bright Spica in the evening sky, while Mars still sits to the lower left of Porrima. Look to the Moon’s upper left to find Zubenelgenubi. Credit: Stellarium/USGS/Celestia/Clementine
- At 11:00 AM EDT, the Moon will be positioned 1.2° south of the star Spica.
- In the evening, a celestial alignment will be visible, with Spica located between Mars and the Moon.
- The double star Alpha Librae (Zubenelgenubi) in the constellation Libra, separable by naked eye (though binoculars or telescopes are recommended), consists of a blue-white primary star (magnitude 2.8) and a fainter orange-yellow companion (magnitude 5.2) separated by 4 arcminutes.
- Sunrise, sunset, moonrise, and moonset times, along with the Moon’s phase (waxing crescent at 19% illumination), are provided for a specific location (40° N 90° W).
The Moon moves 1.2° south of Spica during the daylight hours, sitting due south of Virgo’s luminary at 11 A.M. EDT. By this evening, a new line has formed in the sky, with Spica now between Mars and the Moon, which sits to the star’s left. An hour after sunset, Spica is still some 7° high in the west, so take some time to enjoy the view before the region sets.
While your eyes are on this part of the sky, look to the Moon’s upper left, where you’ll encounter the constellation Libra. Its two brightest stars — Alpha (α) and Beta (β) Librae — are roughly the same magnitude, although Beta is a tad brighter at magnitude 2.6 (Alpha is magnitude 2.8). But Alpha is the one that deserves your attention tonight.
Also called Zubenelgenubi, this is a double star that is within the ability of the naked eye to separate! Its components are 4’ apart, with the brighter of the two shining at magnitude 2.8 and the fainter companion to the northwest, shining at magnitude 5.2. That fainter star is cataloged as Alpha1 Lib, while Zubenelgenubi itself is Alpha2. Even if you have trouble seeing them with your eyes, binoculars or any telescope will readily separate them. With magnification, they form a lovely contrasting pair, as the brighter star shines blue-white and the fainter star orangey-yellow.
Sunrise: 6:23 A.M.
Sunset: 7:39 P.M.
Moonrise: 10:48 A.M.
Moonset: 9:30 P.M.
Moon Phase: Waxing crescent (19%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
For a look ahead at more upcoming sky events, check out our full Sky This Week column.
