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Hera distinguishes its two asteroid targets for the first time

ESA’s Hera spacecraft has resolved Didymos and its smaller companion, Dimorphos, as separate objects for the first time after braking maneuvers slowed its approach. Astronomers found two debris rings separated by a clear gap around the white dwarf J1328−1450, a configuration ESO describes as the first complex system of its kind with potentially two surviving planetesimals. Astronomers examining Vera C. Rubin Observatory data identified 2026 ED138, an icy world currently 46 astronomical units from the Sun, compared with Pluto’s roughly 40. NASA’s Neil Gehrels Swift Observatory stopped science operations after sinking too low to lock onto astronomical targets, following a July rescue spacecraft’s uncontrolled spin before reaching it.

The field note

1 source · 1 item
  1. Two thruster firings reduced Hera’s speed relative to the asteroids to 20 meters per second, enabling a control…
  2. The targets differ substantially in size: Dimorphos measures 151 meters across, compared with 780 meters for Di…
  3. The impact produced a greater deflection than simulations predicted; determining whether it excavated a crater…
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Hera distinguishes its two asteroid targets for the first time

ESA’s Hera spacecraft has resolved Didymos and its smaller companion, Dimorphos, as separate objects for the first time after braking maneuvers slowed its approach. Dimorphos occupies only about one pixel in this image; ESA says the first detailed images will arrive on November 25. [7]

Why it matters

Dimorphos is the first Solar System object whose orbit was measurably shifted by human action, but scientists still need its mass, structure and impact damage to explain the deflection and make kinetic impact a better-understood planetary-defense technique. [7]

Key insights

  • Two thruster firings reduced Hera’s speed relative to the asteroids to 20 meters per second, enabling a controlled approach rather than a rapid flyby. [7]
  • The targets differ substantially in size: Dimorphos measures 151 meters across, compared with 780 meters for Didymos. [7]
  • The impact produced a greater deflection than simulations predicted; determining whether it excavated a crater or reshaped Dimorphos is part of explaining that difference. [7]

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