Star Struck

Entry-level astronomy teaches students just how much our lives are ruled by the sun.

“I got Vega! No, I just lost it…yeah, there it is!”

To passersby on the Green it must be a strange sight: a group of shadowy figures lying in the grass, peering through portable telescopes into the night sky. The figures are students in “Exploring the Universe,” an astronomy course for non-science majors, and this is their lab assignment: They must locate Jupiter, two stars—Vega and Capella—and a double star, Albireo. Then the students must sketch each star as it appears through the telescope.

“Oh my god, there it is, Jupiter—with the moons!” a woman’s voice calls out excitedly. She then falls quiet as she takes in the sight of the remote planet nearly 400 million miles away.

A graduate teaching assistant (TA) guides two students who have lost their way among the stars and reorients them, pointing out how they can find Vega by following the upper wing of the Cygnus constellation. The TA, Jessica Kellar, Adv’12, who studies the formation of stars in remote galaxies, seems as comfortable finding her way among the constellations as she would be navigating the streets in her hometown.

The students have just learned about the Copernican Revolution and Galileo’s observations of the surface of the moon, which shattered previous assumptions about the perfect nature of heavenly bodies and initiated a new, scientific way of looking at the universe. Even modern minds are still moved by the wonders of the night sky. “This is amazing,” says Stella Safari ’13 as she gazes at the rings of Jupiter through the telescope. Safari says one of the reasons she chose to attend Dartmouth was that living in Washington, D.C., she rarely got to see the stars. “When I first came out here for a campus visit,” she says, “I saw shooting stars and I was wowed.”

Professor Brian Chaboyer, who has been teaching “Exploring the Universe” for more than a decade, observes that when you spend some time out in nature, away from city lights, you realize why in ancient times people were so intimately aware of the night sky. He says that for modern humans as well it is important to look up from earth and get some sense of the size of the universe and how humanity fits in.

“It’s good to keep in mind that our lives are ruled by the sun,” says Chaboyer. “Astronomy gives us these vast time scales. You realize human beings have been around for only a fraction of astronomical time. We think of ourselves as a successful species, but where are we going to be in 10 million years?”

How did it all start? How will it end? Are we alone in the universe? These are some of the questions he tries to answer in the course. But to even consider such questions students need to learn to think scientifically, which can be challenging for non-science majors. “Some students haven’t taken math since high school, so there’s definitely a lot of math anxiety,” says Chaboyer.

To bring science to life for non-scientists and to give it a human face, Chaboyer lectures about the history of astronomy and the thinkers who developed theories to explain natural phenomena. Six thousand years ago, he points out, there were observers aware of the 26-year cycle of the moon. More than 2,000 years ago the Greek astronomer Eratosthenes was able to calculate the circumference of the earth. The ancient Greeks assumed the earth was the center of the universe, “not because they were stupid,” says Chaboyer, “but because it was a logical conclusion they drew from their observations.” They had to explain the motion of the celestial bodies without the aid of Newton’s Laws of Motion. The Greeks assumed a universe in which some kind of power was working on the planets to keep them moving. Newton’s laws changed human understanding of the universe by recognizing that objects remain in a state of motion unless force is applied.

In class Chaboyer demonstrates this by pushing a cart over a frictionless air track. With a light poke, the cart slides smoothly across the rail unhampered. Chaboyer’s lectures are enlivened with many such in-class demonstrations and “challenge questions.” He regularly interrupts his talk to bring up a multiple-choice query to which students respond with wireless clickers. The responses are recorded, and students who reply correctly to 80 percent of the in-class questions receive 10 percent extra credit toward their final grade. This encourages students to be actively involved in class, and it is also a way for Chaboyer to determine if he needs to slow down or re-explain a point.

To illustrate the principle of the conservation of energy, Chaboyer holds up a soccer ball and a tennis ball, both of which he bounces off the floor. He then asks the students what would happen if he balanced the tennis ball on top of the soccer ball and bounced them together on the floor. He smiles encouragingly as the students click in their replies, with 80 percent choosing the third option: The tennis ball will rebound up over the professor’s head. The students are on the edges of their seats to observe whether they guessed right. Chaboyer lets go of the balls and the tennis ball shoots up, almost reaching the ceiling.

Chaboyer points out that astronomy is always a back and forth between the observation of phenomena and scientific theories to explain and predict the phenomena. Einstein’s Theory of Relativity, for instance, predicted the existence of black holes, which were observed five decades later. Now relativity is considered as a factor in assuring the accuracy of global positioning systems.

Chaboyer’s research is mostly theoretical and involves the development of models to calculate the age and evolution of stars and ultimately of galaxies. He is also involved in many observation projects to validate and confirm his models. Recently he traveled to South Africa for observations at the Southern African Large Telescope observatory, a powerful telescope funded by Dartmouth in cooperation with other international partners. He also participates in projects using the Hubble Space Telescope to study the ages of the oldest stars in the Milky Way.

Chaboyer recounts how, when he was around 10 years old, the sun was going through a solar maximum, which resulted in a period of spectacular Northern Lights. As a young boy growing up in Winnipeg, Canada, observing those lights dancing in the sky ignited a lifelong interest in astronomy. He dreamed of becoming an astronaut, but as he grew older realized his strength in math and physics equipped him better for a research career. Instead of Northern Lights he became interested in stellar evolution, though he works with colleagues who study the aurora. “I am very lucky that what I do is what I really enjoy,” says Chaboyer.

His enthusiasm rubs off even on those whose primary interests tend to be more anthropocentric and terrestrial. Chantal Shirley ’14, who is considering majoring in sociology with a minor in history, says she took Chaboyer’s class for science credit, thinking she’d learn a bit about the sun and the planets, but she has been surprised by how much the course has influenced her way of seeing things. “There’s so much math in the stars and so much science in the sky,” she says. “I look at it completely differently now.”


Recommended Reading and Web Sites

To learn more about astronomy, Professor Chaboyer suggests the following:

Coming of Age in the Milky Way, by Timothy Ferris (Anchor, 1989): “A very good but older book on the history of astronomy”

The Eerie Silence: Renewing Our Search for Alien Intelligence, by Paul Davies (Mariner Books, 2011): “For anyone interested in extraterrestrial life”

Exoplanets: Finding, Exploring, and Understanding Alien Worlds, by C.R. Kitchin (Springer, 2012): “A reasonable introduction to the search for exoplanets” “Bakersfield College professor Nick Strobel has put an introductory astronomy textbook online” “The website of the magazine Sky & Telescope has a weekly column on what is visible in the sky”

Judith Hertog is a regular contributor to DAM. She lives in Norwich, Vermont.


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