Transit of Venus

astronomy · space events · planetary motion

Super rare event. A transit of Venus happens when our planet Earth, Venus, and the Sun line up perfectly in a straight row. This is incredibly rare because Venus's orbit is tilted compared to Earth's, so most of the time Venus passes above or below the Sun instead of in front of it.

Tiny black dot. When a transit does happen, Venus looks like a small black circle moving slowly across the bright face of the Sun. Even though Venus is almost the same size as Earth, it appears tiny because it's so far away.

Happens in pairs. Transits of Venus come in pairs separated by about 8 years, and then you have to wait more than 100 years before the next pair happens. The last pair was in 2004 and 2012, and the next pair won't occur until 2117 and 2125.

Historical treasure hunt. Before telescopes, scientists didn't know how far away planets were, but by watching transits of Venus from different places on Earth, they could finally calculate the true size of our solar system. This made transits of Venus incredibly important for astronomy hundreds of years ago.