NASA’s Nancy Grace Roman Space Telescope launched on Aug. 30, 2026, beginning a journey that will take it about a million miles from the Earth. Once there, Roman will study some of the biggest mysteries in astronomy, from dark energy to the formation of galaxies. It will also search for planets around other stars, called exoplanets, but in a rather unusual way.

Roman will be able to find many of these exotic worlds without seeing the planets themselves. Instead, it will watch for distant stars that temporarily become brighter.

The reason this strategy works is one of the stranger consequences of Einstein’s theory of gravity: Gravity can bend light. Under the right circumstances, a star – or even a planet – can behave like a natural magnifying glass. The phenomenon is called gravitational microlensing.

As an exoplanet scientist, I study how to detect and learn about worlds far beyond our solar system. One challenge in this field is that no single observing technique can reveal every type of planet. Microlensing is exciting because it functions as a tool that can help astronomers find planets that are difficult to find in other ways.

How can gravity act like a magnifying glass?

Imagine you are looking at a very distant star. Somewhere between you and that star, another star happens to pass almost directly across your line of sight. The two stars may actually be thousands of light-years apart, but from your viewpoint, they appear to line up.

According to Einstein’s theory of general relativity, an object’s mass curves the space around it. Light traveling through that curved space also follows a curved path. So when the foreground........

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