Can you spot the black dot against the yellow-orange sphere? That's Mercury, the smallest planet of the solar system and the closest to our star. On Monday, it made a rare move. /VCG Photo

When earthlings catch Mercury passing across the Sun, it's usually seen moving above or below the star. Once in a blue moon, a transit happens thanks to planetary alignment. This means, Mercury moves in front of the Sun, from the Earth's point of view. To amateur astronomers and space agency scientists, it looks like a tiny black disk traveling across the bright Sun. /VCG Photo

The last time Mercury transited was in 2016, and if you missed Monday's five-and-a-half-hour event, the next one will take place in 13 years' time in 2032. /VCG Photo