Venus and Jupiter are tens of millions of miles apart, but they have been cycling together while moving ever closer to each other this month and are joined by Mercury. This weekend they appear as a bright triangle of light in the western sky beginning about 30 minutes after sunset.

This triple conjunctions is a pretty rare. The last one was in May 2011 and the next one will not occur until October 2015. This weekend’s sky show is a good one because it involves the three brightest planets in May’s night sky, so even observers in cities with bright lights can see them on a clear night.

All three planets will be about 3o degrees apart (the width of your thumb at arm’s length) about 45 minutes after sunset on May 25, 26 and 27. Tonight, Mercury forms the top of the triangle. By Monday, Venus and Jupiter will be side by side, less than 1 degree apart.

As the month ends, Venus and Mercury will climb higher into the evening sky, while Jupiter drops toward the sun.