This animation illustrates the concept of gravitational microlensing. When one star in the sky appears to pass nearly in front of another, the light rays of the background source star become bent due to the warped space-time around the foreground star. This star is then a virtual magnifying glass, amplifying the brightness of the background source star, so we refer to the foreground star as the lens star. If the lens star harbors a planetary system, then those planets can also act as lenses, each one producing a short deviation in the brightness of the source. Thus we discover the presence of exoplanets, and measure its mass and separation from its star.
This animation illustrates two ways a gravitational microlensing event could look to an observer. At top is the way it could appear to a telescope able to resolve the features. The source star appears to move and distort as its light is warped by the closer lensing star and its planet. At bottom is a light curve showing the intensity of light from the event. As the two stars reach best alignment, the signal reaches its peak. The planet orbiting the lensing star is detectable as a brief change in brightness.
This pair of animations compare signals from two planet detection methods – microlensing (top) and transit (bottom) – for high- and low-mass planets. Microlensing signals from small planets are rare and brief, but they’re stronger than the signals from other methods.
The Roman Space Telescope will make its microlensing observations in the direction of the center of the Milky Way galaxy. The higher density of stars will yield more microlensing events, including those that reveal exoplanets.
The Roman Space Telescope will have Hubble-like angular resolution since it will orbit above Earth’s atmosphere, enabling it to separate host and source stars from microlensing events. Its wide field of view will allow the Roman Space Telescope to classify planets’ stars on an unprecedented scale, adding to our understanding of the type of systems throughout the galaxy – including those like our own.