I enjoy a good occultation. Tonight, the gibbous moon occults the star Zuben-el-akrab in Libra. You can watch it snap out of view in a small telescope during the early evening hours. The star is better known as Gamma Librae; the Arabic name translates to “claw of the scorpion,” a reference to the stars of Libra originally being a part of neighboring Scorpius.
Although “visible” across the U.S. and Canada, the best views will be around nightfall in the Eastern Time Zone and in evening twilight in the Central Time Zone. Further west, the occultation occurs before sunset with the sky likely too bright for the star to show. Zuben-el-akrab only shines at magnitude +3.9, unlike the 1st magnitude stars Aldebaran and Spica, which can also be covered by the moon.
Maybe you planned to look at the moon tonight anyway, since the 2-day-past-half phase is absolutely the best time to see the most craters in the best lighting. If you start your explorations early, you can catch the occultation.
Here are a few approximate times, accurate to within a minute or so, when the star will disappear behind the moon’s dark limb. The moon moves east (to the left) with its dark edge approaching the star ever more closely until it disappears in a split second, a most exciting thing to see. Lack of a lunar atmosphere means there’s no transition or slow fading from bright to “utterly gone.” The star will then reappear about an hour to an hour and a half later along the opposite or bright side of the moon.
PS. If you really want to see this and can’t determine a time, please drop me a comment and I’ll send you a customized one.
Cities / Disappearance time (all times are local):
- New York — 10:53 p.m.
- Philadelphia — 10:53 p.m.
- Miami — 11:29 p.m. (barely gets covered by the southern edge of the moon)
- Columbus, Ohio — 10:40 p.m.
- Toronto — 10:39 p.m.
- Indianapolis — 10:35 p.m.
- Chicago — 9:29 p.m.
- Duluth, Minn. — 9:14 p.m.
- Minneapolis — 9:13 p.m.
- Des Moines — 9:18 p.m.
- Denver — 8:00 p.m.