Named for the Roman goddess of love and beauty, Venus is the planet nearest to Earth and the planet second closest to the sun. Due to its brilliance, Venus is recognizable even by people unfamiliar with astronomy. Part of the planet's familiarity has to do with its journey around the sun, making it visible on Earth as the morning or evening star.
A Venusian Year
Venus takes 225 Earth days to orbit the sun. On average, the planet travels about 108 million kilometers (67 million miles) away from the sun during the course of its orbit. Unlike other planets that move along an elliptical path, the path of Venus is almost a perfect circle. Venus is also different than other planets because it spins on its axis in a clockwise motion known as retrograde, rather than counter-clockwise. Venus turns so slowly on its axis that one day on Venus is equal to 243 days on Earth.
Venus appears nearly as bright as the moon as the evening star at one time of year and the morning star at others. This change is due to the differences in time it takes for Earth and Venus to orbit the sun. Every 584 days, Venus passes by the Earth. When Venus has yet to catch up to Earth, it is seen as the evening star. Once it passes, it is seen as the morning star. Venus appears so bright because at only 42 million kilometers (26 million miles) away it is the planet closest to Earth. The swirling clouds covering Venus also add to its brilliance.
A transit occurs when a planet passes between the sun and the Earth. Transits of Venus occur in paired cycles with eight years in between the pairs. The first pair observed after the invention of the telescope were in 1631 and 1639. The most recent pair occurred in 2004 and 2012. Another transit isn't expected until 2117.
Conditions on Venus
Venus, although named for the goddess of beauty, is a vicious place. The atmosphere is a layer of dense clouds that contain water vapor and sulfuric acid. The surface of the planet is marked with craters, extinct volcanoes and shapes that would be continents if the planet had any water to make oceans. Temperatures on Venus hover around 880 degrees Fahrenheit (470 degrees Celsius) with little change in temperature between day and night thanks to the thick blanket of insulating clouds.