Venus, the bright planet that has been a presence in our western sky since winter, is disappearing from view and entering the morning sky. But before it does, it will pass between the sun and the earth and, in an exceedingly rare astronomical event, align with the sun  on Tuesday afternoon.

The transit will be visible on the East Coast shortly after 6 p.m. and won’t happen again until December 11, 2117.

Only those with special solar telescopes will be able to safely watch this incredibly rare event. Casual skywatchers are warned to not look directly at the sun, even late in the day, as serious eye injury can result.

Much of the observing will take place from western United States to Africa. The complete event can be watched in places like Hawaii.