A fantasy encounter was appeared on the sky in the past few days. Earth's neighbour, Venus, passed in front of the Pleiades (also known as the Seven Sisters) star cluster in the constellation Taurus, made this bright cluster into an "Eight Sisters"! Many overseas astronomy enthusiasts have taken pictures of their close encounter.

Venus is one of the planets in the Solar System, its position on the celestial sphere changes every day; the Seven Sisters is an open star cluster composed of distant stars, its position on the celestial sphere almost doesn't change. In the last weekend, Venus was passing in front of the Seven Sisters. Unfortunately, the weather in Hong Kong was bad, we were not able to watch this encounter. However, we can still see the bright Venus in the western sky during the evening in the next two months. Please enjoy if you are interested!

In fact, Venus orbits 13 times around the Sun for every 8 orbits of Earth (The Earth-Venus system performs an orbital resonance of 8:13). Hence, for every 8 years, Earth and Venus will appear an almost the same relative position. The last time when Venus passed closely in front of the Seven Sisters was in early April 2012. Can you guess when will be the next "Eight Sisters" reunion?