One Dot Becomes Two: Hera Finally Sees Both Asteroids
For months, the European Space Agency's Hera spacecraft has been flying towards a pair of asteroids and seeing them as a single dot. On 27 October 2026, ESA announced that had changed: Hera has resolved its two target asteroids separately for the very first time, revealing the binary nature of the Didymos system, currently some 197 million kilometres away from Earth.
The image itself is no great beauty — the smaller asteroid is only around one pixel across. But it is a proof of sight, and it matters enormously, because Hera was built to study the one place in the Solar System where humans have deliberately knocked an asteroid off its course.
A pixel with a history
Hera imaged Didymos and Dimorphos with its monochromatic Asteroid Framing Camera on the evening of 18 October, from 1,280 kilometres away. "With this image the smaller Dimorphos asteroid becomes visible for the first time," explains Michael Kueppers of the mission team. "Before this acquisition the spacecraft was still resolving the Didymos system as a single dot. But now, even though Dimorphos is made up of only around one pixel in this initial image, it is clearly well separated from its parent body."
The two rocks are very different in size. Didymos measures about 780 metres across — a little smaller than Dubai's Burj Khalifa skyscraper, the tallest building in the world. Dimorphos is about 151 metres across, roughly the size of the Great Pyramid of Giza. The pair orbit an average of 1.15 kilometres apart, with Dimorphos circling its parent at about 18 centimetres per second.
The picture came after a pair of braking manoeuvres earlier in October. Two thruster firings, a week apart, slowed Hera to just 20 metres per second relative to its targets, allowing it to approach gradually on a finely tuned path.
The asteroid humans moved
Dimorphos is famous for a reason. On 26 September 2022, NASA's DART spacecraft flew into it at about 6.1 kilometres per second, in the first test of whether a spacecraft impact could deflect an asteroid. The impact shortened Dimorphos's orbit around Didymos by 32 minutes, from 11 hours 55 minutes to 11 hours 23 minutes. Neither asteroid poses a hazard to Earth, before or after the impact — the experiment was a rehearsal for planetary defence, not a response to a threat.
Hera, launched on 7 October 2024, is the follow-up detective. It will measure the mass of Dimorphos, study its interior, examine the impact site and look at what DART did to the moonlet's shape. ESA says the first detailed images of Dimorphos — the first object in the Solar System to have had its orbit measurably shifted by human action — will be unveiled on 25 November 2026, as Hera draws closer and its views grow sharper.
"For the very first time we are seeing through Hera's own eyes the very double asteroid system that the mission was designed and built for," said mission manager Ian Carnelli.
For students, this is a wonderful lesson in how science actually progresses: a single pixel, in the right place at the right time, confirms that a spacecraft's camera, navigation and braking all work — and opens the door to the detailed survey to come. Sometimes the most exciting image is not the prettiest one, but the one that proves you have arrived.
If your child looks up at the night sky and wonders how we could ever move an asteroid, a first lesson in physics or astronomy can take them from gravity and orbits to the missions testing planetary defence for real. Book your first lesson
Sources:
- European Space Agency, "First light: Hera resolves two asteroids instead of one", 27 October 2026: https://www.esa.int/Space_Safety/Hera/First_light_Hera_resolves_two_asteroids_instead_of_one
London Tutors — post your tutoring request and we will match you with a verified tutor.