2011 EO40

2011 EO₄₀ was discovered by Richard A. Kowalski on 10 March 2011 while observing for the Mount Lemmon Survey.^[1][10]

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.^[10] 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.^[11] 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.^[3] 2011 EO₄₀ has an absolute magnitude of 21.5,^[3] which gives a characteristic diameter of about 200 metres (660 ft).^[6]

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.^[7][8][9] 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 (14,260,000 km; 8,860,000 mi),^[3] and it will have a nominal Earth approach on 23 September 2025 at about 0.06 AU (9,000,000 km; 5,600,000 mi).^[3] Asteroid 2011 EO₄₀ 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.^[8]

Future opposition windows are: 7 June 2016 at magnitude 24.5, and 28 May 2018 at magnitude 24.6. 2011 EO₄₀ wasn't observed during either opposition.^[10] The asteroid was recovered on 15 August 2025 by Pan-STAARS.^[12] The best observation window will be on 2–23 September 2025.^[3] Depending on the Earth approach distance (0.04–0.12 AU),^[3] it should be brighter than magnitude 19.^[13]

• Carbonaceous chondrite
• Meteorite