Bennu

Bennu is a near-Earth asteroid designated 101955 Bennu. It is classified as a carbonaceous B-type asteroid and belongs to the Apollo group, meaning its orbit crosses Earth's orbit. Bennu is roughly 490 meters in diameter, has a dark surface, and is believed to be a rubble-pile asteroid that rotates about its axis every about 4.3 hours.

Discovered on September 11, 1999, by the Lincoln Near-Earth Asteroid Research (LINEAR) program, Bennu was named after the Bennu bird of Egyptian mythology, a symbol of creation and rebirth. Its low albedo and carbon-rich composition suggest the presence of primitive materials from the early solar system.

Bennu’s orbit features a semi-major axis around 1.126 astronomical units, an orbital period of approximately 1.19 years, an eccentricity near 0.203, and an inclination of about 6 degrees relative to the ecliptic. Its minimum orbit intersection distance with Earth is on the order of a few hundredths of an astronomical unit, which classifies it as a potentially hazardous asteroid in terms of close approaches. The asteroid is also subject to the Yarkovsky effect, a small but detectable drift caused by thermal forces that influences long-term trajectory.

The OSIRIS-REx mission, launched by NASA in 2016, arrived at Bennu in 2018, collected a sample in 2020, and returned the material to Earth in 2023. Analyses of the sample have provided insights into primitive organic compounds and hydrated minerals, contributing to models of solar system formation and the delivery of volatiles to Earth. Bennu remains a key target for planetary science and planetary defense studies.