Planetary Microlensing

In extremely rare circumstances, exoplanets may be discovered through the observation of a microlensing event. This occurs when the lensing object is a star with a planet orbiting it. As the lensing star passes in front of the background source star, deviations from a standard microlensing event can be observed as extra peaks of magnification caused by the exoplanet. From these deviations, astronomers can infer the existence of a planet around the lens and determine its mass and separation. Planetary microlensing deviations typically last a few hours to a few days. As of January 2022, 121 exoplanets have been discovered using the microlensing method.

OGLE-2011-BLG-0265Lb

Shown below is the light curve of the microlensing event OGLE-2011-BLG-0265Lb, which led to the discovery of a Jupiter-mass planet orbiting an M-dwarf star. The source star is in the Galactic Bulge of the Milky Way, and the intervening lens star with its orbiting planet lies in the Galactic Disk. The planetary system that caused this microlensing event -- a Jupiter-mass companion to a low mass star -- is very rare among known planetary systems and thus the discovery is important for theoretical studies of planetary formation and evolution. The entire microlensing event lasts about 200 days, and the planetary deviation occurs over a 4 day span just before the brightness peaks. The video scans over time (x-axis) and modulates pitch based on magnitude (y-axis). Lower pitch represents dimmer magnitudes.

The light curve data was taken from OGLE, and Skowron et al., 2015, ApJ, 804, 33 (link to paper).