The last time Mercury passed in front of the sun from Earth’s perspective was nearly a decade ago, but on May 9 Mercury will once again transit our nearest star. This is not an event to view with your naked eyes. Looking at the sun is always dangerous, and Mercury is so small (1/158 the size of the sun) that you wouldn’t be able to see it in front of the sun without optical aid anyway.

Experienced astronomers with proper solar filters on their telescopes can view the event directly, but the rest of us will have to settle for images shown online or on TV. Mercury first crosses onto the sun in the morning just before or around sunrise for much of North America. It then takes the small planet seven hours to traverse the disk of the sun before exiting in the early afternoon. Watch news and weather channels for shots of the transit or go to slooh.com for a view. The next transit of Mercury won't be until November 11, 2019.

For sky delights you can safely observe with your own eyes after sunset, try Mars, which pairs with the Full Moon on May 21. Mars’ rival, the reddish Antares (Anti-Ares) is just below Mars; Saturn marks the fourth corner in a slightly lopsided square. Mars reaches opposition on May 22, when it’s opposite the sun and visible all night. The Red Planet shines at a bright -2.1 and appears as a disk through a telescope. Mars’ closest approach to Earth is on May 30, when it's only 0.5 AU away, or 4.2 light-minutes.

The moon isn’t best to view when full, but during earlier stages when it’s already high in the sky by dark and showing its terminator (the line that divides day from night on its surface). On May 14, get out the telescope or binoculars to get a good view of an eight-day-old moon that’s 63 percent illuminated. One cool sight to see will be The Straight Wall, a fault line created by a moonquake long ago. Look near the terminator and just below the equator on the moon, inside a large crater. The wall runs north to south.

On this same night, the moon is close to another fabulous object to spy with binoculars or a telescope: Jupiter. Three of its moons, Io, Europa, and Ganymede, will spread out from their home planet in a line, and over the course of the early evening, Io will disappear behind the giant planet. By late evening, on the opposite side of Jupiter, Callisto and then Io will emerge from behind the planet.