Weighing the invisible: Hubble readies the Roman telescope to hunt gravitational lenses

In a new Hubble image, a galaxy 8 billion light-years away has been stretched into a glowing arc by the gravity of a closer one — a gravitational lens that works as a natural scale for weighing dark matter. NASA is capturing such lenses with Hubble not only for what they reveal now, but to prepare its successor: the Nancy Grace Roman Space Telescope, whose vast field of view will sweep up lenses in bulk, decoded with tools Hubble is training today.

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