Orbit

Venus's orbit lies about midway between those of Mercury and Earth and is inclined some 3 12 to Earth's orbit. Its orbit is almost circular. When Venus is at inferior conjunction (between the sun and Earth), it comes closer to Earth than any other planet. Its farthest distance from the sun is around 67,700,000 miles (108,900,000 km); its nearest is around 66,800,000 miles (107,500,000 km); and its mean (average) distance from the sun is around 67,200,000 miles (108,200,000 km).

Observed with a telescope over a period of months, Venus is seen to pass through phases (apparent changes in shape and size) much like those of Earth's moon. These phases are the result of the changing relative positions of the sun, Venus, and Earth.

Venus may be seen close to the far side of the sun once every 584 days of its orbit. Its sunlit area can be seen then almost in its entirety, but appears to decrease during the rest of its orbit. Also, it seems to grow in size. Only half the planet can be seen around 221 days later, and only a thin area after another 71 days, when it nears the same side of the sun as Earth. Venus rotates very slowly about its axis (a hypothetical line down its center) and completes a full turn in slightly more than one Venusian year (243 Earth days). The direction is east-to-west or retrograde, i.e. opposite to that of all the other planets. The axis tilts at an angle of approximately 178 from the perpendicular position.