HomeOur ScientistsChristopher D. Impey

Our Scientists

Christopher D. Impey, PhD
HHMI Professor / 2014–Present

Scientific Discipline

Physical Science

Host Institution

University of Arizona

Current Research

Towards a Next-Generation Online Science Course

We will develop two new mutually-reinforcing, multi-tiered introductory astronomy courses as models that will demonstrate how to effectively implement evidence-based instructional strategies and assessments on-line, while bridging the gap between formal university-based learning and informal lifelong learning.


Astronomer Christopher Impey studies the changing energy output of supermassive black holes and their relationship with galaxies over cosmic time. These distant and dramatic processes are driven by the same forces that explain the rest of our…

Astronomer Christopher Impey studies the changing energy output of supermassive black holes and their relationship with galaxies over cosmic time. These distant and dramatic processes are driven by the same forces that explain the rest of our universe, and with the right tools, Impey says, scientists have an opportunity to explain their seemingly vast complexity.

That's part of what drew Impey to astronomy as a graduate student, and it is one of the main messages he wants students to take away from the introductory astronomy classes that he teaches. “It's remarkable that, with a small number of fundamental principles, we can reconcile the complex natural world and understand events that happen on such unimaginable scales of time and space,” he says.

Impey grew up in cities, moving from Edinburgh to New York and later London. He never had a “good sky,” he says – so he never peered through telescopes and dreamed of becoming an astronomer. But he loved physics, and studied it as an undergraduate at the Imperial College of Science and Technology in London, where he investigated the nature of matter. During a summer at CERN, the European Organization for Nuclear Research in Switzerland, he did high-energy physics research.

Those fields were exciting, but potentially overwhelming in their scale. Not interested in being swallowed up by a research team with hundreds of members, Impey was instead attracted to the “old-world” nature of astronomy. “You can work as an individual or in a small group,” he says. “You have an idea, go to the telescope and test that idea, and then you write about it.”

Impey earned his PhD in astronomy at the University of Edinburgh. His first major discovery came during his postdoctoral research at the California Institute of Technology, when a survey of faint galaxies led him to discover the largest known spiral galaxy. That galaxy, named Malin 1 after Impey's collaborator, had gone undetected because of its sparse population of stars. He worked for several years to reveal a population of diffuse galaxies that lurked below the brightness of the night sky. In the 1990s, he used quasars – distant sources of intense radiation emerging from supermassive black holes – as flashlights to illuminate the structure of intergalactic medium.

Impey typically spends six or seven nights a year surveying the night sky though large telescopes in Arizona and Chile, seeking a deeper understanding of how objects in the universe evolve. In particular, he's looking for the trigger that makes a supermassive black hole in the center of a galaxy active. Ninety-nine percent of black holes are inactive: most grow slowly despite having plenty of stars and gas to consume. “We used to think black holes were exotic and strange,” he says. “Now we know that every galaxy has a black hole. They are unexceptional. So why are most black holes so unassuming and hard to detect?”

As part of this work, Impey conducted a five-year survey of nearly 700 active galaxies in a piece of sky known as the COSMOS field. His team's finds included galaxies with nuclei only slightly larger and more energetic than the inefficient black hole in the center of the Milky Way. Their observations resulted in the discovery of intermediate-mass black holes at high redshift and suggested that the growth of black holes is self-regulating, tracking closely the growth of their host galaxies.

Impey has taught astronomy at all levels at the University of Arizona, but he is particularly devoted to the introductory classes that he teaches to non-science majors.  Students in these classes don't always have a clear understanding of how science works, and they can be skeptical of its conclusions, Impey says. Those students don't need to be bombarded with data. Instead, he says, his goal is to give them a sense of how scientists know what they know.

Impey is as analytical an educator as he is an astronomer. “It would be perverse to be driven by data in your research life but not let it influence your educational activities,” he says. And the data clearly indicate that students are most engaged when they are actively involved in their own learning. “I wanted to be part of the slow-burning revolution of data-driven education,” Impey says. So he's made his astronomy classes an ever-changing mix of labs, data-rich activities, Socratic dialogs, debates, creative projects, social media, audience surveys, and time in virtual worlds. He hardly ever lectures.

Now, Impey is taking advantage of technology to reach learners all over the world through a massively open online course (MOOC). A pilot class he taught this year on the online learning platform Udemy has attracted more than 21,000 students from more than 180 countries. Next year, he will launch a second course with Coursera, one of the largest MOOC providers, which has a well-developed infrastructure for instruction and evaluation. In keeping with what he's learned about student engagement, activities and group work will be key to the online course, which will be framed around current discoveries in astronomy. A citizen science component will solicit student participation in real astronomy research. He will also use social media to increase engagement.

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  • BSc, physics, University of London
  • PhD, astronomy, University of Edinburgh


  • American Association for the Advancement of Science, Fellow