Grounded in the Stars

Astronomy professor Kelsey Johnson Luca DiCecco

In elementary school, Kelsey Johnson learned two seemingly contradictory facts. One: Fire requires oxygen. Two: Stars are giant balls of fire floating in airless outer space. It was the kind of conundrum that ignited her curiosity about astronomy, and her awe only grew as she learned more about the extraterrestrial environment in which our tiny planet spins. Johnson, who earned a doctorate in astrophysics in 2001 and joined UVA’s astronomy department three years ago, has already chalked up a prestigious National Science Foundation Career Award and a Distinguished Young Investigator Award from UVA. The syllabi for her astronomy classes feature lectures like “Live Fast, Die Young: How Stars Spend Their Lives” and “Supernovae: If It Weren’t for Them, You Wouldn’t Be Here.” In the spring, she’ll pilot a new course, “Unsolved Mysteries of the Universe,” which will explore astronomy’s hot topics.

Johnson investigates the birth of star clusters—extremely dense spherical collections of a million or more stars—by peering deep into space with specialized telescopes that render infrared light and radio waves visible. “The most ancient objects in the universe are globular clusters,” she explains, “and we’re trying to figure out how they were born.”

Astronomy in daily life

In civilizations around the globe, priest-astronomers invented calendars based on the solar year and the cycle of the moon. The Mayan calendar—which begins to count time in approximately 3114 B.C.—more accurately estimated the solar year than the Gregorian calendar, the precursor to the modern Christian calendar.
An understanding of the relationship of the sun, moon and earth allowed astronomers to explain and eventually to predict solar eclipses, which previously had mythical, religious or supernatural explanations. Herodotus documented an eclipse that caused soldiers on both sides of a war to drop their weapons and declare peace in a state of religious ecstasy.
Telescopes are used to track solar flares that might disrupt earth-based communications, damage satellites or cause destructive surges on power grids.
A spin-off of radio astronomy’s interferometry is a system that locates cell phone 911 calls to an accuracy of 500 feet. The arrival times of the phone’s signal at different cell towers are used to triangulate the phone’s location.
To probe the distant galaxies, astronomers use sensors, detectors and amplifiers for electromagnetic energy, from X-rays to ultraviolet rays, that have been adapted to explore the minutiae of the human body. The Lixiscope—a portable X-ray microscope used in neonatology, outpatient surgery and Third World clinics—is NASA’s second largest source of royalties.

Her research employs a range of wavelengths, from optical light to radio waves, to gather information about objects millions of light years away. “Optical light, light that we can see with our eyes, is easily blocked by dust clouds, but longer wavelengths like radio waves can penetrate them and reveal the birth of stars and other phenomena common in the early universe,” she says. “This is significant because it allows us to make hypotheses about our own galactic origins.”

Using these penetrating wavelengths, Johnson estimates the properties and time scales of star formation and draws comparisons among star births in different environments. She and her colleagues were the first to detect natal globular clusters relatively near our own galaxy.

In October, Johnson, 34, received a Packard Fellowship for Science and Engineering, which provides funding for exceptionally creative professors early in their careers. She is particularly interested in reaching out to school-aged children, whose knowledge of nature, she believes, should extend beyond the biosphere. “Learning that we live on a small planet that orbits a minor star in a galaxy of billions of stars that in turn is only one of hundreds of billions of galaxies imparts a necessarily humble sense of perspective and awe,” she says.

In the first few years of her career, Johnson has already made a significant contribution to her field, having uncovered a new means of star formation that occurs under extreme physical conditions. Yet, she displays a humility that must be a byproduct of a life spent staring up into the night sky. “You should see a picture of galaxies colliding,” she says. “It’s breathtaking.”

Night Visions in the Western Hemisphere

Nov. 18: Peak viewing of the Leonids meteor shower. Look toward the constellation Leo in the pre-dawn sky.

Dec. 13-14: Peak of the Geminids meteor shower. Look toward the constellation Gemini. It will be visible most of the night.

Dec. 19: Mars reaches its closest distance from Earth during its orbit. Visible most of the night, near the constellations of Gemini and Orion.

Dec. 22: Winter solstice. As seen from the Northern Hemisphere, the sun is at its lowest in the sky.

Jan. 3-4: Peak of the Quadrintids meteor shower. Look toward the constellation Bootes, which rises in the east around midnight.