A phenomenon known as Venus’ transit will occur this June, one in a series of awesome space-events we’ll get to watch this year.

We’ve already been treated to a meteor shower, a giant, gorgeous “super moon”, and this weekend the western half of the country will be able to see a rare “ring of fire” solar eclipse. But the traveling of Venus across the sun is even more rare, occurring in two transits eight years apart, with 100 years in between each trip. The last transit was in June of 2004, and after the upcoming one, we won’t see another in our lifetime.

Astronomers Without Borders posted an explanation of the occurrence:

“Mercury and Venus are the only planets closer to the Sun than Earth, both moving faster in their orbits and passing us regularly. But rather than crossing directly between us and the Sun, these planets are usually slightly above or below the Sun as we see them. When they line up just right we see the round, black silhouette of the planet slowly crossing the Sun, an even referred to as a “transit.” Mercury transits the Sun 13 or 14 times each century. But Venus transits happen in pairs—two transits eight years apart—with more than 100 years between each pair.”

You can learn more about the phenomenon at Transitofvenus.org, where the event will be live-streamed and you can download a free app which allows users to take part in a global experiment to measure the solar system.