New moon for Milky Way viewing—May 16
To catch May’s astronomical showstopper—the Milky Way core—head out around the night of May 16. The new moon will cast no lunar glow. Pair that with a dark sky, such as those you’ll find in many national parks, and the galactic center will shine at its brightest. It’s also the best time to photograph the Milky Way. The core rises around 11 p.m., depending on your coordinates, and it remains visible until the pre-dawn hours.
The new moon is also an ideal time to view distant galaxies via telescopes. Some of the easiest to see include the Whirlpool Galaxy (near the Big Dipper’s handle) and the Sombrero Galaxy (close to the bright star Spica).
Moon-Venus conjunction—May 18
Don’t miss the sunset on the evening of May 18. Just after it, you can watch the crescent moon and Venus, the sky’s brightest planet, appear in a tight pair. The duo will shine above the western horizon and remain visible for roughly 2 hours. Just as the sky darkens, you can also spot Mercury above the west horizon, with Jupiter above the moon-Venus conjunction, too. (Remember: Only point optical aids west once the sun has fully set.)
A slender crescent moon pairs with brilliant Venus above a line of trees in morning twilight in Qazvin, Iran, in 2014.
Babak Tafreshi, National Geographic Image Collection
A rare “blue moon”—May 31
May closes out with an uncommon lunar event: a second full moon in a single calendar month, often called a blue moon. According to NASA, this occurs about once every two to three years. The blue moon name doesn’t mean our neighbor will actually look blue. Instead, just like the early May moon, it could appear yellowish when it’s near the horizon. Moons typically appear blue only when Earth has certain particles, such as volcanic ash, in its atmosphere.
Use Jupiter to find Gemini—All month
Jupiter shines brightly in the western sky all May; it’s also in the perfect position to help you locate the constellation, Gemini, also known as the twins. The planet sits near the constellation’s two brightest stars, Pollux and Castor. While you can also locate Gemini using another night-sky navigational tool, the Big Dipper, Jupiter offers an especially easy visual cue this month.