101955 Bennu
101955 Bennu has a cumulative chance of around 1-in-1,750 of impacting Earth between 2178 and 2290, with the greatest risk on 24 September 2182. Its mean diameter is 490 m (1,610 ft; 0.30 mi).
Briefing
101955 Bennu (provisional designation 1999 RQ36) is a carbonaceous asteroid in the Apollo group, discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object listed on the Sentry Risk Table, with the second highest cumulative rating on the Palermo scale, and it is named after Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth.
How we know
Bennu has been observed extensively by planetary radar at the Arecibo Observatory and by the Goldstone Deep Space Network, using radar to study the asteroid directly. It was also the target of NASA’s OSIRIS-REx mission: the spacecraft launched in September 2016, arrived at Bennu two years later, and mapped its surface in detail to identify sample-collection sites. From analysis of the orbits, Bennu’s mass and its distribution were calculated, and in October 2020 OSIRIS-REx briefly touched down to collect a sample from the surface before returning a capsule containing that sample to Earth.
- Unseen
- Not described here in terms of naked-eye or amateur visibility; the observations cited are planetary radar (Arecibo, Goldstone) and a spacecraft mission (OSIRIS-REx).
