One of the most exciting advances that has accompanied the detection of exoplanets is the discovery of exomoons—natural satellites orbiting these far away, alien planets. While we know moons to be common in our solar system, we know very little about their formation. Unfortunately, it is difficult to establish the existence of a moon orbiting an exoplanet using the most common method for detecting the planet itself. Most exoplanets are detected by analyzing light curves, very precise measurements of the brightness of light emitted from a star in a range of wavelengths, to determine if there is a predictable, periodic dip in the light curve over time. This dip may indicate that an opaque object—that is, an exoplanet—regularly orbits in front of the star and blocks a fraction of detectable starlight as it does so. Detecting an exomoon involves identifying and separating the individual dips from the exoplanet and exomoon in the detected light curve. These detections of exoplanets and their moons are further complicated by any natural variability of the star’s brightness, as well as variations in the telescope sensitivity over time.

A recent study by David Kipping (Columbia University) and colleagues analyzed light curves collected by the Kepler deep-space telescope of 70 possible exoplanets determined to have a higher likelihood of orbiting satellites. However, even when focusing their study on these favorable candidates, only one possible exomoon emerged: Kepler-1708 b-i. Putative exomoon Kepler-1708 b-i joins one previously detected candidate exomoon, Kepler-1625 b-i, as the first possible natural satellites orbiting planets outside of our solar system. Future analysis with the James Webb Space Telescope will help confirm or deny their existence, potentially helping researchers understand how planetary systems evolve and how they affect the possibility of a planet harboring life. READ MORE