List of asteroid close approaches to Earth in 2011

Asteroids which came closer to Earth than the Moon in 2011 by time of discovery

After closest approach: 19 (59.4%)   < 24 hours before: 1 (3.1%)   up to 7 days before: 10 (31.2%)   > one week before: 0 (0.0%)   > 7 weeks before: 0 (0.0%)   > one year before: 2 (6.2%) Other years 2009, 2010, 2011, 2012, 2013

Below is the list of asteroid close approaches to Earth in 2011.

Timeline of close approaches less than one lunar distance from Earth in 2011

A list of known near-Earth asteroid close approaches less than 1 lunar distance (384,400 km or 0.00257 AU) from Earth in 2011, based on the close approach database of the Center for Near-Earth Object Studies (CNEOS). ^[1]

The CNEOS database of close approaches lists some close approaches a full orbit or more before the discovery of the object, derived by orbit calculation. The list below only includes close approaches that are evidenced by observations, thus the pre-discovery close approaches would only be included if the object was found by precovery, but there was no such close approach in 2011.

This list and the relevant databases do not consider impacts as close approaches, thus this list does not include any of the objects that collided with Earth's atmosphere in 2011, none of which were discovered in advance, but were observed visually or recorded by sensors designed to detect detonation of nuclear devices.

     Rows highlighted red indicate objects which were not discovered until after closest approach

     Rows highlighted yellow indicate objects discovered less than 24 hours before closest approach

     Rows highlighted green indicate objects discovered more than one week before closest approach

     Rows highlighted turquoise indicate objects discovered more than 7 weeks before closest approach

     Rows highlighted blue indicate objects discovered more than one year before closest approach
(i.e. objects successfully cataloged on a previous orbit, rather than being detected during final approach)

Date of closest approach	Date discovered	Object	Nominal geocentric distance (AU) [note 1]	Size (m) (approximate) [note 2]	(H)	Closer approach to Moon	Refs [2] [3]
2011-01-11	2011-01-13	2011 AM37	0.00086  AU (129,000  km ; 80,000  mi )	2.8–6.2	29.9 [4]		data  · 2011 AM37
2011-01-17	2011-01-14	2011 AN52	0.00213 AU (319,000 km; 198,000 mi)	5.1–11	28.6 [5]	Yes	data  · 2011 AN52
2011-01-20	2011-01-24	2011 BY10	0.00238 AU (356,000 km; 221,000 mi)	10–23	27.1 [6]	Yes	data  · 2011 BY10
2011-01-25	2011-01-26	2011 BW11	0.00086 AU (129,000 km; 80,000 mi)	5.8–13	28.3 [7]		data  · 2011 BW11
2011-01-31	2011-02-05	2011 CA4	0.00165 AU (247,000 km; 153,000 mi)	10–23	27.1 [8]		data  · 2011 CA4
2011-02-04	2011-02-04	2011 CQ1	0.000079 AU (11,800 km; 7,300 mi)	1–2.3	32.1 [9]		data  · 2011 CQ1
2011-02-06	2011-02-07	2011 CF22	0.00027 AU (40,000 km; 25,000 mi)	1.8–4	30.9 [10]		data  · 2011 CF22
2011-02-09	2011-02-07	2011 CA7	0.00069 AU (103,000 km; 64,000 mi)	2.3–5.2	30.3 [11]		data  · 2011 CA7
2011-02-23	2011-02-27	2011 DU9	0.00192 AU (287,000 km; 178,000 mi)	12–27	26.7 [12]		data  · 2011 DU9
2011-03-03	2011-03-04	2011 EN11	0.00166 AU (248,000 km; 154,000 mi)	7–16	27.9 [13]		data  · 2011 EN11
2011-03-07	2011-03-05	2011 EY11	0.000876 AU (131,000 km; 81,400 mi)	5.3–12	28.5 [14]		data  · 2011 EY11
2011-03-08	2011-03-10	2011 EM40	0.00162 AU (242,000 km; 151,000 mi)	6.7–15	28.0 [15]		data  · 2011 EM40
2011-03-16	2011-03-15	2011 EB74	0.00219 AU (328,000 km; 204,000 mi)	11–25	26.9 [16]		data  · 2011 EB74
2011-04-06	2011-04-04	2011 GW9	0.00133 AU (199,000 km; 124,000 mi)	6.4–14	28.1 [17]		data  · 2011 GW9
2011-04-06	2011-04-04	2011 GP28	0.00064 AU (96,000 km; 59,000 mi)	3.5–7.8	29.4 [18]		data  · 2011 GP28
2011-05-05	2011-05-08	2011 JV10	0.00232 AU (347,000 km; 216,000 mi)	3.1–6.8	29.7 [19]	Yes	data  · 2011 JV10
2011-06-02	2009-01-16	2009 BD	0.00232 AU (347,000 km; 216,000 mi)	6.4–14	28.1 [20]		data  · 2009 BD
2011-06-27	2011-06-22	2011 MD	0.000125 AU (18,700 km; 11,600 mi)	6.7–15	28.0 [21]		data  · 2011 MD
2011-07-24	2011-08-06	2011 PU1	0.00224 AU (335,000 km; 208,000 mi)	20–45	25.6 [22]	Yes	data  · 2011 PU1
2011-07-28	2011-07-31	2011 OD18	0.00115 AU (172,000 km; 107,000 mi)	13–30	26.5 [23]		data  · 2011 OD18
2011-09-27	2011-09-23	2011 SE58	0.00159 AU (238,000 km; 148,000 mi)	7.3–16	27.8 [24]		data  · 2011 SE58
2011-09-28	2011-10-01	2011 TO	0.00086 AU (129,000 km; 80,000 mi)	13–29	26.6 [25]		data  · 2011 TO
2011-09-30	2011-09-29	2011 SM173	0.00194 AU (290,000 km; 180,000 mi)	7.3–16	27.8 [26]		data  · 2011 SM173
2011-10-12	2011-10-17	2011 UT	0.00152 AU (227,000 km; 141,000 mi)	18–41	25.8 [27]	Yes	data  · 2011 UT
2011-10-17	2009-10-15	2009 TM8	0.00226 AU (338,000 km; 210,000 mi)	5.6–12	28.4	Yes	data  · 2009 TM8
2011-10-26	2011-10-27	2011 UL169	0.00177 AU (265,000 km; 165,000 mi)	5.9–13	28.3 [28]		data  · 2011 UL169
2011-10-28	2011-10-30	2011 UX255	0.00093 AU (139,000 km; 86,000 mi)	8.8–20	27.4 [29]		data  · 2011 UX255
2011-11-08	2005-12-28	(308635) 2005 YU55	0.00217 AU (325,000 km; 202,000 mi)	360	21.9 [30]	Yes	data  · 2005 YU55
2011-12-03	2011-12-08	2011 XC2	0.00232 AU (347,000 km; 216,000 mi)	61–140	23.2 [31]	Yes	data  · 2011 XC2
2011-12-28	2011-12-29	2011 YC40	0.00071 AU (106,000 km; 66,000 mi)	3.1–7	29.6 [32]		data  · 2011 YC40
2011-12-29	2012-01-01	2012 AQ	0.00180 AU (269,000 km; 167,000 mi)	1.9–4.3	30.7 [33]		data  · 2012 AQ
2011-12-30	2011-12-31	2011 YC63	0.00161 AU (241,000 km; 150,000 mi)	4.2–9.4	29.0 [34]		data  · 2011 YC63

Warning times by size

This sub-section visualises the warning times of the close approaches listed in the above table, depending on the size of the asteroid. The sizes of the charts show the relative sizes of the asteroids to scale. For comparison, the approximate size of a person is also shown. This is based the absolute magnitude of each asteroid, an approximate measure of size based on brightness.

Absolute magnitude H ≥ 30 (smallest)

Silhouette of man standing and facing forward

(size of a person for comparison)

Absolute magnitude 30 > H ≥ 29

Absolute magnitude 29 > H ≥ 28

Absolute magnitude 27-28

Absolute magnitude 27 > H ≥ 26

Absolute magnitude 26 > H ≥ 25

Absolute magnitude 25 > H (largest)

•   After closest approach: 1 (50.0%)
•   < 24 hours before: 0 (0.0%)
•   up to 7 days before: 0 (0.0%)
•   > one week before: 0 (0.0%)
•   > 7 weeks before: 0 (0.0%)
•   > one year before: 1 (50.0%)

See also

• List of asteroid close approaches to Earth
• List of asteroid close approaches to Earth in 2010
• List of asteroid close approaches to Earth in 2012

Notes

1. Distance from the center of Earth to the center of the object. See the NASA/JPL Solar System Dynamics Glossary: Geocentric. Earth has a radius of approximately 6,400 km.
2. For asteroids without a well determined size an albedo of 0.05 is assumed. An albedo of 0.05 establishes an approximate upper limit to the size of the asteroid.

References

1. "NEO Earth Close Approaches". NASA/JPL CNEOS. Retrieved 27 February 2025.
2. "JPL Small-Body Database Browser". JPL Solar System Dynamics. NASA Jet Propulsion Laboratory. Archived from the original on 2006-06-12.
3. "MPC Database". IAU Minor Planet Center. International Astronomical Union. Retrieved 1 January 2021.
4. "JPL Small-Body Database Browser: (2011 AM37)" (2011-01-14 last obs).
5. "JPL Small-Body Database Browser: (2011 AN52)" (2011-01-17 last obs).
6. "JPL Small-Body Database Browser: (2011 BY10)" (2011-01-30 last obs).
7. "JPL Small-Body Database Browser: (2011 BW11)" (2011-01-28 last obs).
8. "JPL Small-Body Database Browser: (2011 CA4)" (2011-02-10 last obs).
9. "JPL Small-Body Database Browser: (2011 CQ1)" (2011-02-04 last obs).
10. "JPL Small-Body Database Browser: (2011 CF22)" (2011-02-07 last obs).
11. "JPL Small-Body Database Browser: (2011 CA7)" (2011-02-08 last obs).
12. "JPL Small-Body Database Browser: (2011 DU9)" (2011-03-11 last obs).
13. "JPL Small-Body Database Browser: (2011 EN11)" (2011-03-05 last obs).
14. "JPL Small-Body Database Browser: (2011 EY11)" (2011-03-07 last obs).
15. "JPL Small-Body Database Browser: (2011 EM40)" (2011-03-14 last obs).
16. "JPL Small-Body Database Browser: (2011 EB74)" (2011-03-15 last obs).
17. "JPL Small-Body Database Browser: (2011 GW9)" (2011-04-05 last obs).
18. "JPL Small-Body Database Browser: (2011 GP28)" (2011-04-05 last obs).
19. "JPL Small-Body Database Browser: (2011 JV10)" (2011-05-10 last obs).
20. "JPL Small-Body Database Browser: (2009 BD)" (2011-06-20 last obs (arc=2.4 yr)).
21. "JPL Small-Body Database Browser: (2011 MD)" (2011-07-03 last obs (arc=12 days)).
22. "JPL Small-Body Database Browser: (2011 PU1)" (2011-09-21 last obs (arc=46 days)).
23. "JPL Small-Body Database Browser: (2011 OD18)" (2011-08-08 last obs).
24. "JPL Small-Body Database Browser: (2011 SE58)" (2011-09-27 last obs).
25. "JPL Small-Body Database Browser: (2011 TO)" (2013-01-12 last obs (arc=1.28 yr)).
26. "JPL Small-Body Database Browser: (2011 SM173)" (2011-09-30 last obs).
27. "JPL Small-Body Database Browser: (2011 UT)" (2011-11-24 last obs (arc=38 days)).
28. "JPL Small-Body Database Browser: (2011 UL169)" (2011-10-31 last obs).
29. "JPL Small-Body Database Browser: (2011 UX255)" (2011-11-01 last obs).
30. "JPL Small-Body Database Browser: (2005 YU55)" (2011-12-16 last obs).
31. "JPL Small-Body Database Browser: (2011 XC2)" (2011-12-30 last obs (arc=22 days)).
32. "JPL Small-Body Database Browser: (2011 YC40)" (2011-12-30 last obs).
33. "JPL Small-Body Database Browser: (2012 AQ)" (2012-01-03 last obs).
34. "JPL Small-Body Database Browser: (2011 YC63)" (2012-01-01 last obs).