Venus is the second planet from the Sun and is often called Earth's "sister" or "twin" due to its similar size, mass, and structure. Despite these similarities, Venus is the hottest planet in the Solar System, with surface temperatures reaching between 438 °C to 482 °C (820 °F to 900 °F) due to a runaway greenhouse effect caused by its thick atmosphere composed mainly of carbon dioxide. Venus has no moons and rotates in the opposite direction compared to most planets, resulting in a very long day of about 243 Earth days, which is longer than its year of about 225 Earth days. The atmospheric pressure on Venus is about 92 times that of Earth, equivalent to pressures found 1 km below Earth's oceans, and it experiences sulfuric acid rain that never reaches the surface. Winds in its atmosphere can reach speeds up to 300 km/h (186 mph). Venus is named after the Roman goddess of love and beauty. Multiple space missions have landed on Venus, facing brief operational lifetimes due to harsh surface conditions. Venus is also the brightest planet seen from Earth after the Moon and is visible to the naked eye.