Maximum elongation

Maximum elongation

Fig. 6.1 . Unlike the planets that orbit the Sun beyond the Earth, Mercury and Venus can never be seen high in the sky in the dead of night. Because they are close to the Sun and inside Earth's orbit, these planets are always seen soon after sunset, or shortly before sunrise, and they show phases much as the Moon does. The elongation of Mercury and Venus, or their angular distances from the Sun as viewed from the Earth, never exceeds 28 degrees and 47 degrees, respectively.

Copyright 2010, Professor Kenneth R. Lang, Tufts University