NASA’s TESS exoplanet-hunter has uncovered a planet that was hiding in its own archive, using a detection method rooted in Albert Einstein’s theory of general relativity. The find marks a novel approach to spotting distant worlds beyond our solar system.
The newly identified planet was revealed through gravitational microlensing, a phenomenon where a foreground star's gravity bends and magnifies light from a background star. This technique, predicted by Einstein, allows telescopes like TESS to detect planets that would otherwise remain invisible against their host star's glare.
TESS typically finds exoplanets by observing the tiny dips in brightness when a planet transits its star. But this object did not produce a transit signal. Instead, scientists re-analyzed archival data from the spacecraft, applying microlensing algorithms that picked out the subtle distortion in starlight caused by the hidden world.
The discovery demonstrates that microlensing can be used effectively by a space telescope not specifically designed for it. It opens the door to finding many more non-transiting planets already recorded in TESS data, potentially multiplying the mission's yield without requiring new observations.
A caveat remains: microlensing events are rare and often fleeting, requiring precise timing and extensive follow-up to confirm planets. The technique also works best for certain orbital configurations, so it will not replace but rather complement TESS’s primary transit method.