Saturday, July 13, 2024

Half-Moon Occults Spica (evening)

On Saturday afternoon, July 13, the waxing gibbous moon will be visible crossing the bright, southeastern sky. For observers across North and Central America, the Caribbean, and west to the eastern tip of Russia, the moon will pass in front of, or occult, Virgo's brightest star, Spica, after dusk. In the Eastern Time Zone, the dark, leading edge of the moon will begin to occult Spica just before they set in the west. Observers in the Central and Mountain Time Zones will see the entire occultation in a dark sky. For those located even farther west, the event will occur in a bright sky. Lunar occultations of bright stars can be seen with sharp, unaided eyes in a dark sky, and through binoculars and backyard telescopes, even when the sky is bright. Exact times for this event depend on your location, so use an app like Starry Night to
look up your circumstances. You can also use the app to simulate where on the lit half of the moon the star will re-appear. In Denver, Colorado, the dark limb of the moon will cover Spica at 8:48:45 p.m. CDT. The star will emerge near Mare Crisium at 10:10:28 p.m. CDT.


Consecutive Shadows Cross Jupiter

From time to time, observers with good quality telescopes can watch the small, round, black shadows of the Galilean moons traverse Jupiter's disk. On
Saturday morning, July 13, sky-watchers located in western North America can watch two shadows cross the southern hemisphere of Jupiter, one after the other. At 2:49 a.m. PDT (or 09:49 UT), the small shadow of Europa will begin
to cross Jupiter's south polar zone. As it is leaving Jupiter's disk at 5:10 a.m. PDT (or 12:10 UT), Io's larger shadow will begin its own crossing. By the time its trip is complete, around 7:19 a.m. PDT (or 14:19 UT), the sky will be brightening.


First Quarter Moon

The moon will complete the first quarter of its orbit around Earth, as
measured from the previous new moon, on Saturday, July 13 at 6:49 p.m. EDT or 3:49 p.m. PDT and 22:49 UT. The 90-degree angle formed by the Earth, sun, and moon at that time will cause us to see our natural satellite half-illuminated on its eastern side. At first quarter, the moon always rises around mid-day
and sets around midnight, allowing us to see its pale orb in the afternoon daytime sky, too. The evenings surrounding the first quarter phase are the
best ones for viewing the lunar terrain when it is dramatically lit by low- angled sunlight.

(Data courtesy of Starry Night)
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