Yesterday was the last time in my lifetime that I will be able to see Venus transit across the sun. In case you missed it, The Guardian has a great play by play, along with interesting facts and history about the transit, and Bad Astronomy has a slew of great resources including everything you needed to know about it, a beautiful gallery, and this amazing “video” of the 1882 transit,
But why is the transit of Venus such a big deal? Quite simply, the transit of Venus reveals the secrets of the Universe. In the 1700’s Edmond Halley (yes that Halley) realized that by observing transits from widely spaced locations on Earth, it should be possible to triangulate the distance to Venus, and thus begin to be able to measure distances in the Solar system. The finer details are nicely described in this NASA produced video,
Halley’s call to action galvanized scientists, who set off on expeditions around the still largely unexplored world to view a pair of transits in the 1760s. These expeditions would prove quite daunting. Perhaps for no one more so than Guillaume Le Gentil, whose ordeal is tragically recapped over at Sidereal Times, but to sum it up, he travelled thousands of miles from France to the South Pacific, he faced bloody battles, dysentery, and hurricanes, but was defeated by clouds. He stayed overseas to catch the following transit, but missed it due to fatigue and fever. He returned home, defeated and broken, only to find he had been declared dead, his wife had remarried, his position had been replaced, and his estate had been auctioned off. All of this, for the chance to view this transit.
While the transit was of great importance to early astronomers, it remains an important event for modern astronomers as well. By examining the atmosphere of Venus as it transits the Sun, astronomers will gain valuable information that will aid in their search for exoplanets that may have atmospheres. When a planet with a thick atmosphere (like Venus) passes in front of a star, the atmosphere absorbs some of the light. Different elements in the atmosphere will absorb light differently, having an impact on the observed spectrum from the star. These differences allow astronomers to determine the composition of the atmosphere, and maybe even if a planet is M-Class. In addition to the great scientific benefits that the transit of Venus presents, there is perhaps no greater benefit than the fact that this event has opened the eyes of millions of people to the amazing wonders of the Universe. I was fortunate enough to view this transit in an auditorium at the University of Guelph, which had a live feed from their rooftop observatory. Somewhat to my surprise the auditorium was full, and maybe equally surprising it was full with a lot of young children. These kids were witnessing an awesome event, one that will likely not happen again in their lifetime, and they were doing so with the aid and ease of technology. Between the live stream from NASA and various smartphone apps, it has never been easier to be a backyard astronomer, surely if early astronomers, particularly Le Gentil, knew how easy we had it, they would be rolling in their graves.