101955 Bennu (provisional designation ) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the highest cumulative rating on the Palermo Technical Impact Hazard Scale. It has a cumulative 1-in-1,800 chance of impacting Earth between 2178 and 2290 with the greatest risk being on 24 September 2182. It is named after the Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth. has a mean diameter of and has been observed extensively by the Arecibo Observatory planetary radar and the Goldstone Deep Space Network. Bennu was the target of the OSIRIS-REx mission which is intended to return its samples to Earth in 2023 for further study. On 3 December 2018, the OSIRIS-REx spacecraft arrived at Bennu after a two-year journey. It orbited the asteroid and mapped out Bennu's surface in detail, seeking potential sample collection sites. Analysis of the orbits allowed calculation of Bennu's mass and its distribution. In October 2020, OSIRIS-REx successfully touched down on the surface of Bennu, collected a sample using an extendable arm, secured the sample and prepared for a return trip to Earth. On 10 May 2021, OSIRIS-REx successfully completed its departure from the Bennu asteroid while still carrying the sample of the asteroid rubble. Discovery and observation Bennu was discovered on 11 September 1999 during a Near-Earth asteroid survey by the Lincoln Near-Earth Asteroid Research (LINEAR). The asteroid was given the provisional designation and classified as a near-Earth asteroid. Bennu was observed extensively by the Arecibo Observatory and the Goldstone Deep Space Network using radar imaging as Bennu closely approached Earth on 23 September 1999. Naming The name Bennu was selected from more than eight thousand student entries from dozens of countries around the world who entered a "Name That Asteroid!" contest run by the University of Arizona, The Planetary Society, and the LINEAR Project in 2012. Third-grade student Michael Puzio from North Carolina proposed the name in reference to the Egyptian mythological bird Bennu. To Puzio, the OSIRIS-REx spacecraft with its extended TAGSAM arm resembled the Egyptian deity, which is typically depicted as a heron. Its features will be named after birds and bird-like creatures in mythology. Physical characteristics Bennu has a roughly spheroidal shape, resembling a spinning top. Bennu's axis of rotation is tilted 178