Exoplanets are planets beyond our Solar System. Speculated to exist for centuries, the first exoplanets were only discovered in the 1990s. But since then, thousands of exoplanets have been discovered and confirmed, and that list grows longer every month. So, some of these exoplanets must be like Earth, right? Well, we still don’t know if that’s true! The easiest exoplanets to find are worlds that orbit very close to their parent stars, and are often fiercely hot, or massive gas giants like Jupiter and Saturn in our own Solar System. No exoplanet like Earth that orbits a Sun-like star has yet been found.
But the European Space Agency, or ESA, aims to find Earth-like exoplanets with a space mission called Plato, an acronym for Planetary transits and oscillations of Stars. Like NASA’s successful Kepler and TESS missions, Plato will discover exoplanets through the transit method. This relies on the fact that, if the orbit of an exoplanet is aligned with its parent star along our line of sight, then it will slightly dim that star’s light, as the exoplanet appears to cross in front of, or transit, the star. The amount of stellar dimming is tiny, and it’s best to measure it from space, above Earth’s turbulent atmosphere.
Plato will use a group of twenty-six, wide-field cameras that record data at rapid intervals to detect planetary transits. Plato differs from past exoplanet missions in several ways. Plato will study some of the brightest and closest stars, allowing for detailed follow-up studies with large ground-based telescopes and other space telescopes. Plato will stare at the same wide expanses of our Galaxy for up to 3 years, long enough to observe several transits of exoplanets in Earth-like orbits about Sun-like stars. Plato will also observe oscillations in stars, so that methods from the new field of asteroseismology can be used to determine the structure, composition, and age of the parent stars. Data from Plato and follow- up studies with other telescopes will be used to determine diameters, masses, densities, orbital periods, temperature ranges, and perhaps even atmospheric compositions and biosignatures for Earth-like exoplanets.
The Plato Mission is scheduled to launch in early 2027 into a solar orbit about 1 million miles from Earth, from which it will operate for 4 to 8 years. Let’s hope for a successful launch and deployment of Plato, so that we can learn if some nearby exoplanets could potentially support life.
Music written and produced by Kenny Mihelich. Western Slope Skies is produced by the Colorado Mesa University Astronomy Club, the Western Slope Dark Sky Coalition, and KVNF Community Radio. This feature was written and voiced by Art Trevena.