Astronomers around the country tonight will be watching a little black dot move in front of the sun for several hours in a rare event known as the Transit of Venus. Wheaton College astronomer A.J. Poelarends says the school’s observatory has the best equipment to view the event, which last occurred in 2004 and before that in 1882. The next one won’t come until 2117.
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“We can very much see the features on the surface of the sun like arches of gas floating above the surface of the sun, big flames and those kinds of things,” he says. The best part? It’s free and open to the public from 4:30 until the sun sets at around 8:30. Poelarends says the 19th Century transit helped astronomers better understand the solar system. He says people previously understood the general order of the planets, but didn’t know distances between planets or between planets and the sun. “[The last time] a pair of those transits took place, people stood out on ships all over the whole world,” he says.