It's one of the big questions science has yet to answer: whether there is intelligent life somewhere out there, on another planet in the universe. Astrobiology is the science and study of that question.

Transits of Venus - where the planet is visible as a tiny black dot slowly crossing the sun - are rare. The next one is happening on Tuesday, June 5th, and will be visible from North America, for a few hours just before sunset. After that, it won't happen again for 105 years.