Coming soon, to a sky near you: The Transit of Venus


Astrophysicist extraordinaire Summer Ash stopped by our office today to introduce us to the wonders of the “Transit of Venus”.
Don’t be frightened! It’s not a bad sci-fi movie,  but a rare, celestial spectacle: Venus will pass across the Sun, directly in our line of sight.

And you really don’t want to miss it, because it will be your last chance to catch it until … 2117. Which means you will never get another chance. 

So mark your calendars for Tuesday, June 5 at 6:30pm ET. Basically, the farther west you are, the more of the transit you’ll be able to see. To figure out your visibility based on your location, here’s a helpful guide. (If you’re in New York, astronomers from Columbia University will be stationed at Union Square and Adam Clayton Powell Boulevard at West 125th Street – more details here and on their twitter.)

Now, this could be neat just for the geeky, planetary coolness of it all. “Honey, grab the kids and get out the telescope! A rare spectacle!”

But it’s also cool because our entire understanding of the solar system relies on this very event.


We measure the size of our solar system in Astronomical Units (AUs)

1 AU = approx. 93 million miles = the distance between the Earth and the Sun.

Astronomers first figured out that “93 million miles” part thanks to calculations from the transit of Venus back in 1882!

As Summer says, astronomer Edmund Halley (of “Halley’s comet” fame) figured out way back in 1716 that we could calculate the distance between the Earth and the Sun by timing how long it takes Venus to cross the Sun

In 1882, astronomers were finally able to get themselves to the right place at the right time to observe the transit, and a few years later the scientific community accepted the unit of measurement of approx. 93 million miles - a value which we continue to use today (refined with modern radar measurements!)

While astronomers no longer need to observe the transit of Venus to determine the distance to the Sun, astronomers are still super excited to see how our current observations differ or improve upon those early observations from the 19th century. As Summer notes above:

“…the reason it’s so exciting right now is because we have completely different technology as astronomers. Back then, they had telescopes but they were doing a lot more hand calculations, they didn’t have cameras to capture the images. We’ve got satellites in space now, so astronomers are really “geek-ing” out about this.”

Remember: safety first! Never look directly at the sun – and follow these guidelines from NASA to ensure safe viewing.


Rachel Maddow Show Geek

Coming soon, to a sky near you: The Transit of Venus