Gravitational lensing is an optical phenomenon caused by light being bent by gravity as it travels from the source to the observer.
In 3190, Commander Paul Stamets observed that a miniature working model of the Dark Matter Anomaly aboard the USS Discovery was behaving exactly like the original, including gravitational lensing and dark matter accretion. (DIS: "The Examples")
When the DMA threatened the Sol system later that year, at one point Ensign Sylvia Tilly estimated from gravitational lensing that it would strike Earth in two hours. (DIS: "Coming Home")