Venus is the second planet from the Sun. It is a rocky planet with the densest atmosphere of all the rocky bodies in the Solar System, and the closest in mass and size to its orbital neighbour Earth. Orbiting inferiorly, it always appears close to the Sun in Earth's sky, as either a "morning star" or an "evening star". While this is also true for Mercury, Venus appears more prominent, since it is the third brightest object in Earth's sky after the Moon and the Sun. Venus has historically been a common and important object for humans, in both their cultures and astronomy.