Hera separates Didymos and Dimorphos in its first resolved view
Hera has distinguished Didymos and its smaller companion Dimorphos as separate bodies for the first time. The image released on 27 October marks a step in the spacecraft’s approach after braking maneuvers. Closer observations will investigate the physical changes left by the DART impact in 2022, including the smaller asteroid’s mass and structure.
Science··Midday
The asteroid pair separates into two points
Hera, the European Space Agency’s planetary-defence spacecraft, has distinguished Didymos and its smaller companion Dimorphos as separate objects for the first time.[1], [2]
Earlier views from the spacecraft showed a single point. The newly released image therefore reveals the binary system itself as Hera approaches the pair, which is about 197 million km from Earth.[1]
The monochrome Asteroid Framing Camera took the image on 18 October from about 1280 km away. Dimorphos covers roughly one pixel, but its light is clearly separated from the larger asteroid. ESA released the view on 27 October. The exposure date precedes the public release, and the fine surface observations are still to come.[1]
Braking prepares a closer approach
A pair of braking burns a week apart earlier in the month reduced Hera’s speed relative to the asteroids to about 20 metres per second. The spacecraft can then approach with smaller adjustments. Didymos is approximately 780 metres across and Dimorphos about 151 metres. Their average separation is 1.15 km; the smaller body travels around its companion at about 18 centimetres per second. Those dimensions describe the two targets that Hera will examine at closer range.[1]
Hera will investigate the DART impact site
NASA’s Double Asteroid Redirection Test, or DART, struck Dimorphos on 26 September 2022 at 6.1 km per second. The planetary-defence experiment shortened its orbital period by about 33 minutes and threw material into space. Hera’s investigation will measure the smaller asteroid’s mass, composition and internal structure, helping establish how its physical properties influenced the observed deflection.[1]
The team also wants to establish whether the collision left a crater or reshaped the asteroid more broadly. Several instruments and two small companion spacecraft are planned for the close survey. ESA intends to unveil detailed images of Dimorphos on 25 November. The initial resolved view marks an approach milestone; those measurements and the detailed assessment of the impact remain mission objectives.[1]
The DART collision left a debris plume extending across about 10,000 km of space. Hera’s close investigation is intended to connect that large-scale response with the target’s properties and the physical effects of the impact.[1]
