The Sky As we speak on Saturday, October 4: Io and Europa overlap

Jupiter’s moons Io and Europa overlap as they start to transit the gasoline big early this morning, following their shadows throughout.

Io and Europa overlap (with smaller Europa showing in entrance) as the 2 moons start a transit of Jupiter on Oct.4. Ganymede lies east of Jupiter and Callisto lies to the west, outdoors the sector of view proven right here. Credit: Astronomy: Roen Kelly

Jupiter’s Galilean moons usually transit the planet’s disk one by one — tonight, nonetheless, Io and Europa cross the disk collectively. The two moons even seem to partially overlap as their transits start early this morning at 4:04 a.m. EDT, with smaller Europa passing in entrance of bigger Io. 

You’ll spot brilliant Jupiter excessive within the east round this time, to the decrease proper of Castor and Pollux in Gemini (the planet outshines the 2 stars). Make certain to get your telescope out early — round 3:30 A.M. EDT, Io and Europa are approaching Jupiter from the east, however their shadows are already crossing the disk. Europa’s shadow is nearest the western limb, whereas Io’s is nearer to the jap limb (and the 2 moons). The moons’ transit begins at 4:04 A.M. EDT, with Europa’s shadow slipping off the other limb 13 minutes later. 

Keep watching as Io shortly pulls forward of Europa; the volcanic moon is on a smaller, closer-in orbit round Jupiter, and thus strikes quicker throughout the face of the planet. By the time Io’s shadow disappears at 5:03 A.M. EDT, the 2 moons are effectively separated and Io is roughly midway throughout the disk. Continue watching the moons so long as you possibly can; all the U.S. ought to have the ability to catch Io’s exit round 6:20 A.M. EDT, though the sky is rising brilliant for these on the East Coast. Europa’s transit ends round 5:53 A.M. CDT, proper round dawn within the Eastern time zone. 

Sunrise: 7:00 A.M.
Sunset: 6:37 P.M.
Moonrise: 5:25 P.M.
Moonset: 3:53 A.M.
Moon Phase: Waxing gibbous (92%)
*Times for dawn, sundown, moonrise, and moonset are given in native time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. native time from the identical location.

For a glance forward at extra upcoming sky occasions, take a look at our full Sky This Week column.