Venus is the hottest planet in our Solar System, with a staggering surface temperature of 475 deg C - even though it is the second farthest away from the Sun. This is because of Venus’ atmosphere, which is extremely dense and is made of carbon dioxide and huge clouds of sulphuric acid. That, along with 1000s of active volcanoes, makes it to where this dense atmosphere acts as a blanket: it doesn’t just allow heat directly coming from the Sun to enter, but it also traps it without letting it reflect back. Effectively, this is what causes the planet to become quite hot.