ESA's Hera sees Didymos and Dimorphos apart for the first time

Europe's planetary defence mission has reached a milestone you can measure in pixels. ESA's Hera spacecraft has, for the first time, imaged the asteroid Didymos and its small moon Dimorphos as two separate objects, ESA announced on 27 October.

What Hera actually saw

The picture was taken on the evening of 18 October by Hera's monochromatic Asteroid Framing Camera, at a distance of about 1,280 km from the pair. The system itself is currently some 197 million km from Earth.

Until this shot, the two bodies blurred into a single dot. Now Dimorphos shows up as roughly one pixel, but ESA's Michael Kueppers says it is clearly separated from its parent. The image follows two braking burns, fired a week apart earlier this month, that slowed Hera to about 20 m/s relative to the asteroids so it can creep closer in controlled steps.

Why these two rocks matter

• Didymos is about 780 m across; Dimorphos is about 151 m, roughly the size of the Great Pyramid of Giza.
• The pair orbit an average 1.15 km apart, with Dimorphos moving at about 18 cm/s.
• On 26 September 2022, NASA's DART spacecraft deliberately hit Dimorphos at 6.1 km/s, shortening its orbit by around 33 minutes — the first time humans measurably shifted the path of a Solar System object.

DART proved a "kinetic impactor" can nudge an asteroid. What it could not show is what the hit did to Dimorphos itself: whether it left a crater or reshaped the whole body, and what its mass and structure are. Those answers decide how reliably the technique could be used against a real threat.

What comes next

Mission manager Ian Carnelli says the views will sharpen quickly. ESA plans to publish the first detailed images of Dimorphos on 25 November. Over the following months Hera will run a close-up "crash site investigation", release two shoebox-sized CubeSats for an even closer look, and eventually attempt a landing.

For more deep-space science, see our explainer on what a dark galaxy is and our report on the Spider crater impact structure in Australia. If you want to spot asteroids and planets yourself, start with our beginner telescope guide.