The Western Hemisphere will be able to view Venus crossing the sun this evening, a last-in-a-lifetime opportunity. In Mexico events are scheduled today across the capital.
The ancient Maya, famed for their knowledge of astronomy and highly precise calendar, closely followed the movements of Venus – possibly including the planet’s rare transits across the sun.
Now modern Mexico gets to view this last-in-a-lifetime planetary show tonight, along with the rest of the western hemisphere, when Venus will travel across the sun, appearing like a freckle on the face of our distant star.
“Venus will pass between the earth and the sun, creating a small shadow,” says Alejandro Farah, an astronomer with Mexico’s National Autonomous University.
There won’t be another chance to see this phenomenon for another 105 years. Mercury circles the sun fast enough that its shadow can be seen across the sun every 13 to 14 years. However, the tilted orbit of Venus makes its transit exceedingly rare. The transits occur in pairs spread eight years apart, separated from the next pair by more than a century. The last set was visible in 1874 and 1882. Tonight's phenomenon is the second of a pair (the first was in 2004) and won't be seen again until 2117.
For viewers in Mexico City, the second planet from the sun will make its move at approximately 5 p.m.
While June weather in the capital is typically hot and clear during the day, rain showers and thunderstorms often obscure the late afternoon sky. Weather.com predicts “scattered showers” for the capital beginning around 3 p.m. But, as often happens in the sprawling metropolis, rain may fall in one borough while the sun shines on another.