The second planet from the Sun, with a diameter about 400 miles less than that of Earth. Venus is a terrestrial or inner planet and at inferior conjunction comes nearer to Earth than any other planet; depending on its phase, it is also the brightest object in the night sky aside from Earth's moon. Because Venus is an inferior planet (located between Earth and the Sun), it is only visible relatively near the horizon in the first few hours before sunrise or after sunset. It has a dense atmosphere consisting primarily of carbon dioxide, which, together with its proximity to the Sun, creates an intense greenhouse effect, making it the hottest planet in the solar system with an average surface temperature of 464°C (867°F). Venus is completely shrouded by a thick layer of clouds made up mainly of droplets of sulfuric acid with other clouds of vaporous and particulate sulfur dioxide below it. Radar mapping of the Venutian surface shows rolling hills, plains, and numerous volcanoes as well as large impact craters and extensive lava flows.