The new moon of May occurs on May 26. Two days later the moon will make a close pass to Jupiter in the evening sky, and the summer constellations will be rising.
New moons happen when the moon is directly between Earth and the sun. They share a celestial longitude (called right ascension by astronomers), a projection of the Earth's longitude lines on the sky measured eastward from the point where the sun crosses the celestial equator. This position is also called a conjunction. If the sun and the moon line up perfectly the result is a solar eclipse; but that does not happen most of the time, as the moon's orbit is tilted 5 degrees relative to Earth's orbit. (The next solar eclipse is due on Sept. 21).
