2011 EO40

 is an asteroid, classified as a near-Earth object and a potentially hazardous asteroid of the Apollo group. It is a possible candidate for the parent body of the Chelyabinsk superbolide.

Discovery, orbit and physical properties
was discovered by Richard A. Kowalski on 10 March 2011 while observing for the Mount Lemmon Survey.

Its orbit is typical of Apollo asteroids and is characterized by significant eccentricity (0.54), low inclination (3.36º), and a semi-major axis of 1.65 AU. Upon discovery, it was classified as an Earth crosser, a near-Earth asteroid (NEA) and a potentially hazardous asteroid (PHA) by the Minor Planet Center. It was listed on the Sentry Risk Table for less than one day. Its orbit is in need of additional observations to determine if it is part of an asteroid family; as of October 2015 the orbit is determined using just twenty observations spanning an observation arc of 34 days. has an absolute magnitude of 21.5, which gives a characteristic diameter of about 200 m.

Relationship to the Chelyabinsk superbolide
Recent calculations indicate that this object is a plausible candidate to be the parent body of the Chelyabinsk superbolide, since its orbit is very similar to the computed, pre-impact path of the Chelyabinsk meteoroid. It has relatively frequent close encounters with Venus, the Earth–Moon system, and Mars. It had a close encounter with Earth on 28 January 2011 at 0.0953 AU, and it will have a nominal Earth approach on 23 September 2025 at about 0.06 AU. Asteroid experiences close approaches to the Earth–Moon system following a rather regular pattern, every 17 years approximately due to the combined action of multiple secular resonances.

Visibility
Future opposition windows are: 7 June 2016 at magnitude 24.5, and 28 May 2018 at magnitude 24.6. The best observation window will be on 2–23 September 2025. Depending on the Earth approach distance (0.04–0.12 AU), it should be brighter than magnitude 19.