An Evening of Exoplanets

Princeton University astrophysics professor Josh Winn discussed exoplanets, how they are detected and studied, and why scientists find them fascinating during an Evening of Science sponsored by the Loomis Chaffee Physics Club on April 14.

Exoplanets are planets in solar systems other than our own, and astronomers so far have detected about 4,500 of them, Professor Winn explained to the 20 inquisitive students who attended the Zoom session.

We cannot see exoplanets even when using the most advanced telescope technology because the planets are so far from Earth and so much dimmer than the stars around which they orbit, he said. But scientists have developed other, physics-based methods for detecting these distant planets, and he explained these methods and their formulaic bases in detail.

In addition to revealing more about the universe, the discovery of exoplanets and detection of their properties and movement help scientist to better understand our own solar system. For instance, Professor Winn said, although the Earth and other planets in our solar system follow nearly circular paths as they orbit the Sun, not all planets orbit stars in circles. Many have more elongated orbits, and some travel dramatically closer to and farther from their suns at different points of their orbits, changing speeds based on their distance from the sun and its gravitational pull. Not all solar systems have their planets arranged on roughly the same plane as their sun’s equator, either, he said.

Scientists also can measure the density of an exoplanet, its orbital wave, and even the tilt of the planet on its axis, he noted, adding that the latter quality has become a particular obsession of his research group. For large exoplanets, experts can identify what substances are in their atmospheres, and they hope eventually to be able to do so for planets as small as the Earth.

Professor Winn said an ongoing NASA project called the Transiting Exoplanet Survey Satellite will be the source of most exoplanet discoveries in the next few years, and all of the data from the project is publicly available, enabling anyone to use the data to look for celestial bodies. “It really is a frontier mission,” he said.

A physicist and astronomer, Professor Winn joined the Princeton faculty as a professor of astrophysical sciences in 2016 after 10 years on the physics faculty at M.I.T. He earned his bachelor’s and master’s degrees and his doctorate in physics from M.I.T. He was a participating scientist in the NASA Kepler mission, and he is a co-investigator for the Transiting Exoplanet Survey Satellite mission.

The Loomis Chaffee Physics Club is led by junior Lillie Szemraj.