Which planet in our solar system spins the slowest, completing a full rotation once every 243 Earth days?
And the answer: Venus.
As the second planet from the sun, Venus completes one rotation every 243 Earth days. In other words, one day on Venus equals 243 days on Earth. That's by far the slowest rotation of any planet in our solar system.

You may think you know just about everything there is to know about our neighboring planet, Venus, but this curious sister of Earth has tricks around every corner. Test your knowledge below.
Q: Which planet is hotter: Mercury or Venus?
A: Venus! Despite being further away from the sun than Mercury, the high amounts of carbon dioxide in Venus' atmosphere create an incredibly inhospitable atmosphere. Its mean temperature is around 863 degrees Fahrenheit. Whew!
Q: Does Venus have a higher or lower atmospheric pressure as compared to Earth?
A: Higher. Much, much higher in fact. Venus has 90 times the atmospheric pressure of Earth.
Q: Who is Venus named after?
A: The Roman goddess of love and beauty. It's thought that Venus was named for the goddess of beauty due to her brilliant shine in the night sky. Of the five planets known to ancient astronomers, it would have been the brightest.
Q: After the moon, which object in our solar system shines the brightest in the night sky?
A: And again... Venus! Venus' clouds of sulfuric acid make it incredibly reflective in the daytime and at night. They don't call it the morning and evening star for nothing!
Learn more about our twin planet below.
