Venus is the second planet from the Sun in the modern heliocentric order.
Its orbit lies between Mercury and Earth, at an average distance of about 0.72 astronomical units from the Sun. Venus is a terrestrial, or rocky, planet and is broadly similar to Earth in size and mass, which has led to the nickname “Earth’s sister planet.”
That resemblance can be misleading. Venus has a dense carbon-dioxide atmosphere, persistent sulfuric-acid clouds, and an average surface temperature near 464 °C. Its powerful greenhouse effect makes it far hotter than Mercury’s average surface, despite Mercury being closer to the Sun.
Venus is also easy to confuse with the brightest star-like object in the sky. It is commonly called the morning star or evening star, depending on whether it appears before sunrise or after sunset, but it is a planet. Venus has no natural moon and rotates backward relative to most planets, taking about 243 Earth days to complete one rotation while orbiting the Sun in about 225 days.