By Heidi Toth
NAU Communicationseclipse


Ty Robinson is spending his first day at his new job as a professor at Northern Arizona University standing outside watching the sky.

Of course, it is for the solar eclipse on Aug. 21 and he is an astronomer, so the change in venue for the day makes sense.

Robinson studies exoplanets, planetary climate, habitability and astrobiology, recently focusing on using data and models from the Earth, atmosphere and planetary sciences to create better modeling techniques for exoplanets. He is a member of the NASA Astrobiology Institute’s Virtual Planetary Laboratory and the Goddard Institute for Spaces Studies NExSS team.

He discusses how the eclipse can explain planetary behavior, which may eventually lead to detecting alien life, what it may tell alien life about us and why this celestial event really is worth going outside and putting on your eclipse glasses.

What will we experience from our vantage point in Flagstaff?

Flagstaff is going to see a 70 to 80 percent reduction in sunlight during the partial eclipse and, because of the brief drop in sunlight, outside temperatures may drop for a short amount of time.

What can we learn from this eclipse?

Eclipses offer a great way to discuss how we detect and study exoplanets, which are worlds that orbit stars other than our sun. For exoplanets, we sometimes catch them “transiting” their host star. When aligned like this, the exoplanet casts its shadow on Earth, just like the moon will do during the eclipse. Through these transit events, we learn about exoplanet’s size relative to its host star, and we can learn about the atmospheric composition of this distant world. We can learn what an atmosphere is made of because a transiting exoplanet will appear larger (and cast a slightly bigger shadow) at colors where its air blocks more light because of absorption by gases or clouds. Also, the timing between transit events tells us about the orbit of the planet, because the orbital frequency is related to the orbital distance.

Observing lots of transiting exoplanets, like NASA’s Kepler mission did, tells us about how many planets there are in our galaxy and how often certain planets “occur.” We can answer questions like: Are planets on Earth-like orbits rare or common? Are giant planets orbiting close to their host star rare or common? If we get atmospheric information from transits, we learn gases make up the air on a world. We can also figure out the temperature of a planet, and we can learn what the planet’s atmosphere is made of. At some point in the future, maybe with NASA’s upcoming James Webb Space Telescope, these exact techniques may help us find life on other worlds.

partial solar eclipse

In a March 2015 solar eclipse, within the penumbra, the eclipse is partial (left), but within the umbra, the moon completely covers the sun (right). Photo by NASA Goddard Space Flight Center

If aliens were watching Earth from another planet, what would this eclipse look like to them?

If you think of Earth’s orbit like a pancake with the sun at the middle, then any distant stars that look back along the edge of that pancake get to see Earth transit the sun one once every year. The transits would look a bit weird because our moon is rather large, so the effects of the moon transiting the sun while the Earth also transits the sun would be observable. If an alien observer happensto be looking at our sun while the Earth is transiting and the moon passes between Earth and the sun, the moon temporarily disappears from the alien’s view.

Why should I make a special effort to be part of this eclipse?

Solar eclipses aren’t super uncommon, but they also aren’t super common. We should enjoy them when we can, especially if the event is going to impact nearly the entire U.S. It’s a neat opportunity to participate in an event that will span our entire country and which has excited (or intrigued or scared) human beings for ages.

What’s unusual about this eclipse is its path is across the entire length of the United States. Many portions of the continental U.S. haven’t witnessed a total solar eclipse for nearly 40 years, much less one with such a long path across our country.

The solar eclipse in Flagstaff will begin at 9:13 a.m. Aug. 21, with maximum coverage at 10:34 a.m. It ends at 12:01 p.m.