Which Two Inner Planets Can Be Viewed From Earth As They Cross the Face of the Sun?

Orbits

• Mercury and Venus both orbit the sun. If both of their orbits were identical to Earth's orbit, transits across the sun would occur and be seen much more frequently. However, since their orbits are at a slight angle to Earth's orbit, these direct transits occur very rarely.

Mercury Transits

• Mercury transits directly across the sun about a dozen times every century. These dozen transits only occur in either May or November.

Venus Transits

• Venus transits directly across the sun in pairs very rarely. These two transits occur within eight years of each other, and more than a century passes before another pair of transits occur.

Viewing a Transit

• A transit can be viewed using specially designed "solar glasses" or a telescope. If you plan on using a telescope, you must use a specially designed solar filter to attach to your telescope before attempting to directly observe the sun. You can also use your telescope to create a projection of the sun. To do this, use the shadows on the ground to align your telescope with the sun. Make sure you do not look into the telescope at any time. Once aligned, place a sheet of white paper behind the eyepiece. You will then be able to see the sun on the sheet of paper. You may need to adjust the focus of your telescope.