Jupiter’s largest moon seemingly disappears as it slides into the giant planet’s shadow to start the week, while a waning crescent Moon passes near Venus to wrap it up.
Friday, May 24
Head outside late this evening and you can’t miss Jupiter. The giant planet rises before 10 p.m. local daylight time and climbs highest in the south around 2 a.m. Jupiter shines at magnitude –2.6, which makes it the brightest point of light in the sky until Venus rises in morning twilight. The planet currently resides among the much dimmer background stars of the constellation Ophiuchus the Serpent-bearer. A telescope reveals dramatic cloud features on the gas giant’s 46″-diameter disk as well as the four bright Galilean moons. And tonight provides a rare opportunity to see the solar system’s largest satellite disappear. As Jupiter rises, Ganymede appears west of the planet. If you keep watching, however, you’ll see the moon slowly fade from view. At 1:41 a.m. EDT, Ganymede starts to enter Jupiter’s shadow while it is still 16″ from the planet’s limb. The moon is so big that it takes 14 minutes to disappear completely.
Saturday, May 25 Binoculars open a world of wonders invisible to the naked eye. Did you realize you could see several galaxies without resorting to a telescope? One of the spring sky’s best is the Blackeye Galaxy (M64) in Coma Berenices. This constellation stands high in the south once darkness falls. The 8th-magnitude spiral galaxy appears about 1° northeast of the 5th-magnitude star 35 Comae Berenices. M64 is barely in range of 50mm binoculars under a dark sky, although you’ll need 80mm or larger binocs or a telescope to spot the dark dust lane that gives the galaxy its “black eye.”
Sunday, May 26 Last Quarter Moon occurs at 12:34 p.m. EDT. When it rises around 2:30 a.m. local daylight time tomorrow morning, it will appear slightly less than half-lit. Earth’s only natural satellite then appears against the background stars of Aquarius the Water-bearer