A Neighborly Journey

Thanks to our proximity to the sun, we can see only three planetary bodies passing across the face of our home star. The moon does it most frequently, two to five times a year, causing solar eclipses. Mercury traverses the sun far less often—only 13 times per century. And then there is Venus, whose solar transits are rarest of all. Venus’s orbit is tilted 3.4 degrees with respect to ours, so from Earth’s point of view, it usually slides by either above or below the sun. In fact, no living person has ever seen a Venus crossing; the last one happened in 1882. But astronomers—and anyone else who’s curious—can observe this extraordinary spectacle on the morning of June 8.