Asteroid Observation
Hubble sees no dust trail from active asteroid Bennu
Deep observations at a favorable viewing geometry find no ejecta and set mass-loss limits well below the activity typically detected from Earth.
Briefed October 7, 2026 · Aliens in the Clouds
Preprint · Constraining Non-Detection
OSIRIS-REx saw Bennu release particles at close range, establishing it as an active asteroid. David Jewitt, Max Mutchler, and Yoonyoung Kim used Hubble to look from afar during a 2023 orbit-plane crossing, when any trail should be favorably aligned, and found no ejected material in the near-nucleus profile or along the projected orbit.
The non-detections constrain mass loss to below 0.12 kilograms per second near the nucleus and below 0.006 kilograms per second from the absent trail, with both limits depending on the adopted dust model. Those rates sit one to two orders of magnitude below activity measured remotely for other active asteroids. Bennu can therefore be active while remaining effectively invisible to a distant telescope.
Why it matters
A well-characterized null result measures the blind spot in remote surveys. It cautions against equating ‘no visible dust’ with ‘inactive’ when classifying small bodies or comparing them with interstellar visitors.
What the source establishes
Fresh preprint submitted October 6 using 2023 Hubble data. The absence of a trail is observed; translating brightness limits into kilograms per second requires assumptions about dust size and scattering.
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