Venus is the hottest planet of the Solar System. Naturally, you would expect Mercury to be the hottest planet, but you got it wrong! Venus is. Why? Because even though Mercury is the closest planet to the Sun, it has no atmosphere, no volcanic eruptions, nothing! Venus has a very thick atmosphere and a lot of volcanic eruptions. As all the heat in Venus is not able to escape the planet due to the atmosphere, this makes it the hottest planet in the Solar System. It glows red hot because of this only. It is also called Earth's Evil Twin as it is almost the same size as the Earth. Since it glows red hot, it looks like a star at night and therefore is also called the evening star. Venus has a diameter of 12,104 kilometers, making the radius about 6,051.8 kilometers. It is at a distance of 107.55 million kilometers from the Sun. Venus has a central iron core and a rocky mantle, similar to the composition of Earth. Its atmosphere is mainly made up of Carbon Dioxide (96%) and Nitrogen (3%), with small amounts of other gases. Venus has even longer days than Mercury. One day on Venus would be equal to 115 days, 18hrs! One year here is is equal to 225 Earth days.