Gravitational Microlensing Method

The light from a distant star is bent towards the Earth because of the presence of a star system passing between the Earth and the star.

Albert Einstein’s Theory of General Relativity taught us that gravity causes a distortion of space-time. Thus a large mass, such as a star, causes the fabric of space to bend around it, in the same way that a bowling ball on a mattress will deform it. Gravity can therefore bend and focus light, just like the lens of a magnifying glass.

The gravitational microlensing method allows planets to be found using light from a distant star. The path of the light from this star will be altered by the presence of a massive lens – in our case, a star and a planet. Thus, for a short period of time, the distant star will appear brighter.

In the video, the trajectory of the light emitted by the star in the background is changed as the lens – the star and planet system – passes in front of the distant star. The star becomes momentarily brighter for an observer on Earth.

Credit : NASA

Astronomers can’t predict where or when in the sky this type of event is going to happen. Therefore, it is necessary to observe a large number of stars for a long period of time to discover planets using the gravitational microlensing method.