Hera reaches the asteroid pair that a NASA spacecraft struck, shortening a moonlet's orbit by 33 minutes

Background

Planetary defence is back in view as a European spacecraft reaches the asteroid pair that humans once nudged. Hera is the European Space Agency's planetary defence mission, and it has taken its first close picture of the Didymos system. Didymos is a binary asteroid: the parent body is about 780 m across and its moonlet Dimorphos is about 151 m across, with roughly a kilometre between them. NASA's DART spacecraft, weighing 580 kg and travelling at about 6.1 km a second, struck Dimorphos on 26 September 2022 and shortened its orbit around Didymos by 33 minutes, far more than had been expected. Hera's framing camera took the new image from 60 km away, and the spacecraft is now 196.8 million km from Earth. The aim is to turn a single experiment in deflecting an asteroid into a method that is understood well enough to use again.