Mercury, transits, and K'nex

Posted by Korey Haynes
on Monday, May 09, 2016

There's a little black spot on the Sun today. // Credit: NASA/Bill Ingalls

I hope you got a chance to enjoy the transit of Mercury today! Most of the world had at least some chance to see it (sorry, Australia), and here in Wisconsin, we could view the whole event — or, we could have, if the weather had cooperated.

I spent the day at Yerkes Observatory. The clouds were patchy, but we had solar telescopes for checking out the Sun directly, and projection boxes for a different kind of experience. Inside, we were running the SLOOH livestream, which I hope you got a chance to enjoy if your weather was likewise uncooperative. And whenever the Sun peeked out, some volunteer would come running in to draw visitors back outside to the real deal.

As you probably noticed from photos and videos shared today, Mercury is tiny compared to the Sun’s face, and easily confused with a sunspot if you’re not careful. But this in itself is an awesome lesson in the truly staggering size of the solar system members.

Here I am demonstrating my orrery, complete with live sensor readings in the background! // Credit: Korey Haynes

While the transit of Mercury is a fun observing event, there’s not a lot of science that comes out of it. But transits of solar system objects are a great segue into my favorite science topic: exoplanet transits. The same chance alignment that let us watch Mercury crawl across the Sun’s face also lets us detect exoplanets in far-out star systems. So we ran activities at the Mercury observation today that taught visitors about the power of exoplanet transits.

I used the event as an excuse to build a project I’ve long dreamed about, but could never seem to find the time or inclination to dive into: making my own transit system. The Kepler team has kept a list of projects that use Legos or similar toys to build an orrery — a mock solar system. By adding a light sensor that simulates Kepler’s watchful eye, you can reasonably replicate the exoplanet-hunting experience.

I made my orrery out of K’nex, with clay planets, a Maglite + ping pong ball star, and a guitar stand to hold my “star” in place. Definitely a DIY project!

After visitors investigated my Kepler model, we encouraged them to apply their newfound understanding and check out the Planet Hunters project, where they could analyze real Kepler data. Even if you missed an event today, you can still try this part right at home.

I hope you enjoyed your Mercury transit day as much as I did. And if you missed the whole thing, then never fear: NASA has you covered.

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