OBSERVING 3 NIGHT: Regulus, the brightest star in Leo, shines near the waxing gibbous Moon. May 2017 5 PREDAWN: The Eta Aquariid meteor shower, often the Southern Hemisphere's strongest of the year, should be at its best before dawn today and tomorrow. From mid-northern latitudes, few or no Aquariids are visible. DUSK: Tiny Mars gleams 6° north (upper right) of Aldebaran, low in the west-northwest. 7 NIGHT: Look for Jupiter's yellow-white light about 3° right of the nearly full Moon. Blue-white Spica twinkles some 9° below or lower left of the pair. 11 NIGHT: A double shadow transit occurs on Jupiter from 9:59 p.m. to 10:06 p.m. Eastern Daylight Time. 18 NIGHT: A double shadow transit occurs on Jupiter from 11:53 p.m. to 12:43 a.m. EDT. 22 DAWN: The waning crescent Moon hangs about 3° or 4° lower right of Venus. 25 NIGHT: A double shadow transit occurs on Jupiter from 10:47 p.m. to 12:20 a.m. Pacific Daylight Time. 29 EVENING: Go out at dark to seek the waxing crescent Moon in the west. The Beehive Cluster (M44) sparkles about 3° to its upper right. 31 EVENING: The first-quarter Moon is high in the southwest at sunset. As twilight deepens, look for the bright spark of Regulus 5° or 6° right of the Moon. UGC 8335 (Arp 238) consists of a pair of interacting galaxies, their spiral forms distorted and stretched by the proximity of their gravitational fields. See more on colliding galaxies on page 28. N ASA / ESA / H U B B LE HE R ITAG E TE A M (SCTSCI / AU R A ) / A . E VA N S ( U N I V E R S IT Y O F V IRG IN I A / N R AO / STO N Y B RO O K U N I V E R S IT Y ) s k y a n d t e l e s c o p e .c o m * MAY 2017 41http://www.skyandtelescope.com