- Venus is the second closest planet to the Sun, and it is located between Earth and Mercury. It is about 12,100 km in diameter, and it is 41,840,000 km away from Earth. Venus takes 225 days to rotate around the sun. The surface of Venus is rocky and dusty and is covered with mountains, plains and canyons. There is also a river of hardened lava. Venus is sometimes referred to as Earth's sister planet because they are close together and similar in size.
- Italian astronomer Galileo first observed the phases of Venus 1610 through one of the world's first telescopes. His observations disproved the Ptolemaic system, which stated that Earth was the center of the solar system. Galileo's observations also provided evidence that the Copernican system, which stated that the Sun was the center of the solar system, was correct. Because Galileo defended the Copernican system, he went against the Roman Catholic Church, and they placed him on house arrest until his death in 1642.
- Venus shows in several phases depending on how close it is to the Sun. When Venus is between the Earth and the Sun, it is at inferior conjunction and cannot be seen because the illuminated side is facing away from Earth. More of Venus' illuminated side faces Earth as it moves, and the sunlit surface is called a phase. When the illumination of Venus is growing, it is called waxing. When it becomes almost completely lit by the sun, Venus disappears due to the Sun's brightness. This is called superior conjunction, when the Sun lies between Venus and Earth. During the second half of Venus' orbit around the Sun, illumination decreases. This is called waning. It appears to the east of the Sun when viewed from Earth.
- Venus is so bright against a dark sky when using a telescope that it is best to observe the planet in bright twilight. Venus can be seen in the thin crescent phase with binoculars when it is in the nearer part of its orbit to the Earth, usually in the morning or evening sky. Venus can be seen in daylight if it is clear of the sun and there is a clear sky. The best way to see Venus in daylight is when it is a Morning Star (when it is seen in the Eastern sky before sunrise).