First light: Hera resolves two asteroids instead of one

The European Space Agency's Hera spacecraft has captured the first detailed images of the Didymos binary asteroid system, revealing the previously unseen smaller asteroid Dimorphos. The Didymos-Dimorphos pair resides 197 million kilometers (122 million miles) from Earth. Hera resolved Dimorphos, a 151-meter (495-foot) asteroid, as one pixel in its initial image taken from a distance of 1,280 kilometers (795 miles).

Prior to this, Hera's imaging had depicted the entire system as a single dot. Following successful braking maneuvers, Hera came within 1,280 km of the asteroid pair, enabling this groundbreaking observation. The smaller Dimorphos, akin in size to the Great Pyramid of Giza, orbits Didymos at an average distance of 1.15 km (0.71 miles) at a relative speed of 18 cm/s (7.1 inches per second).

Key to this mission is its role in planetary defense, as Hera will conduct a close-up investigation of Dimorphos to assess how the asteroid's orbit was altered by NASA's DART spacecraft, which intentionally impacted the smaller asteroid in September 2022, shifting its orbit by approximately 33 minutes. The data collected will provide critical insights into the effectiveness of kinetic impact as a planetary defense technique, including the asteroid's mass, structure, and composition.