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99942 Apophis

Updated: 12/11/2025, 4:38:34 PM Wikipedia source

99942 Apophis (provisional designation 2004 MN4) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size. Observations eliminated the possibility of an impact on Earth in 2029, when it will pass the Earth at a distance of about 38,000 kilometres (23,600 mi) above the surface. It will also have a close encounter with the Moon, passing about 96,000 km from the lunar surface. There was a brief period of concern in December 2004 when initial observations indicated a probability of 0.027 (2.7%) that the asteroid would hit Earth on Friday, April 13, 2029. A small possibility nevertheless remained that, during its 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole estimated to be 800 metres in diameter, which would have set up a future impact exactly seven years later on Easter Sunday, April 13, 2036. This possibility kept it at Level 1 on the 0 to 10 Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small and Apophis's rating on the Torino scale was lowered to Level 0. By 2008, the keyhole had been determined to be less than 1 km wide. During the short time when it had been of greatest concern, Apophis set the record for highest rating ever on the Torino scale, reaching Level 4 on December 27, 2004. It is estimated that an asteroid as big or bigger coming so close to Earth happens only once in 800 years on average. Such an asteroid is expected to actually hit Earth once in about 80,000 years. Preliminary observations by Goldstone radar in January 2013 effectively ruled out the possibility of an Earth impact by Apophis in 2036 (probability less than one in a million). In February 2013 the estimated probability of an impact in 2036 was reduced to 7×10−9. It is now known that in 2036, Apophis will approach the Earth at a third the distance of the Sun in both March and December, about the distance of the planet Venus when it overtakes Earth every 1.6 years. Simulations in 2013 showed that the Yarkovsky effect might cause Apophis to hit a "keyhole" in 2029 so that it will come close to Earth in 2051, and then could hit another keyhole and hit Earth in 2068. But the chance of the Yarkovsky effect having exactly the right value for this was estimated as two in a million. Radar observations in March 2021 helped to refine the orbit, and in March 2021 the Jet Propulsion Laboratory announced that Apophis has no chance of impacting Earth in the next 100 years. The uncertainty in the 2029 approach distance has been reduced from hundreds of kilometres to now just a couple of kilometres, greatly enhancing predictions of future approaches. Entering March 2021, six asteroids each had a more notable cumulative Palermo scale rating than Apophis, and none of those has a Torino level above 0. However, Apophis will continue to be a threat possibly for thousands of years until it is removed from being a potentially hazardous object, for instance by passing close to Venus or Mars.

Infobox

Discovered by
mw- Roy A. TuckerDavid J. TholenFabrizio Bernardi
Discovery site
Kitt Peak
Discovery date
June 19, 2004
MPC designation
(99942) Apophis
Pronunciation
/əˈpɒfɪs/ or /əˈpoʊfɪs/; (trad.) /ˈæpəfɪs/
Named after
Ἄποφις Apophis
Alternative designations
2004 MN4
Minor planet category
mw- .inline, .inline dl, .inline ol, .inline ul, dl dl, dl ol, dl ul, ol dl, ol ol dd dd dd , dd dt , dd li , dt dd , dt dt , dt li , li dd dd dd , dd dt , dd li , dt dd , dt dt , dt li , li dd dd ol li AtenNEOPHA
Adjectives
Apophidian /æpəˈfɪdiən/ (Latin Apŏpidis)
Symbol
(rare)
Observation arc
6599 days (18.07 yr)
Earliest precovery date
March 15, 2004
Aphelion
1.0987 AU (164.36 million km)
Perihelion
0.7461 AU (111.61 million km)
Semi-major axis
0.9224 AU (137.99 million km)
Eccentricity
0.1911
Orbital period (sidereal)
0.886 yr (323.6 d)
Average orbital speed
30.73 km/s
Mean anomaly
90.28°
Mean motion
1.112°/day
Inclination
3.341°
Longitude of ascending node
203.9°
Argument of perihelion
126.7°
Earth MOID
0.000038 AU (5.7 thousand km)[a]
Jupiter MOID
4.1 AU
TJupiter
6.464
Dimensions
0.370 km (0.230 mi)0.45 × 0.17 km
Mean radius
0.185 km (0.115 mi)0.17±0.02 km
Mass
6.1×1010 kg (assumed)
Mean density
3.2 g/cm32.6 g/cm3 (assumed)
Synodic rotation period
30.4 h (1.27 d)30.55±0.12 h30.67±0.06 hTumbling:27.38±0.07 h (precession period), 263±6 h (rotation period), 30.56±0.01 h (twice the period of harmonic with strongest lightcurve amplitude)
Geometric albedo
0.230.35±0.10
Temperature
270 K
Spectral type
Sq
Absolute magnitude (H)
19.7±0.419.09±0.1918.95±0.15

Tables

Selected approaches to Earth till 2117[1] · Orbit
2004-12-21
2004-12-21
Date
2004-12-21
JPL SBDBnominal geocentricdistance (AU)
0.09638 AU (14.418 million km)
uncertaintyregion(3-sigma)
n/a
2013-01-09
2013-01-09
Date
2013-01-09
JPL SBDBnominal geocentricdistance (AU)
0.09666 AU (14.460 million km)
uncertaintyregion(3-sigma)
n/a
2029-04-13
2029-04-13
Date
2029-04-13
JPL SBDBnominal geocentricdistance (AU)
0.000254115 AU (38,015.1 km)
uncertaintyregion(3-sigma)
±3.3 km
2036-03-27
2036-03-27
Date
2036-03-27
JPL SBDBnominal geocentricdistance (AU)
0.309678 AU (46.3272 million km)
uncertaintyregion(3-sigma)
±130 thousand km
2051-04-20
2051-04-20
Date
2051-04-20
JPL SBDBnominal geocentricdistance (AU)
0.04149 AU (6.207 million km)
uncertaintyregion(3-sigma)
±240 thousand km
2066-09-16
2066-09-16
Date
2066-09-16
JPL SBDBnominal geocentricdistance (AU)
0.06943 AU (10.387 million km)
uncertaintyregion(3-sigma)
±870 thousand km
2116-04-12
2116-04-12
Date
2116-04-12
JPL SBDBnominal geocentricdistance (AU)
0.01756 AU (2.627 million km)
uncertaintyregion(3-sigma)
0.00104 to 0.10433 AU (0.156 to 15.608 million km)
2117-10-07
2117-10-07
Date
2117-10-07
JPL SBDBnominal geocentricdistance (AU)
0.48 AU (72 million km)
uncertaintyregion(3-sigma)
0.30994 to 0.64045 AU (46.366 to 95.810 million km)
Date
JPL SBDBnominal geocentricdistance (AU)
uncertaintyregion(3-sigma)
2004-12-21
million km)
n/a
2013-01-09
million km)
n/a
2029-04-13
0.000254115 AU (38,015.1 km)
±3.3 km
2036-03-27
million km)
±130 thousand km
2051-04-20
million km)
±240 thousand km
2066-09-16
million km)
±870 thousand km
2116-04-12
million km)
million km)
2117-10-07
million km)
million km)
Orbital elements for 2029 (pre-flyby) and 2030 (post-flyby)[55] · Orbit › 2029 close approach
Units
Units
Parameter
Units
Semi-majoraxis
AU
Perihelion
(°)
Pre-flyby
Pre-flyby
Parameter
Pre-flyby
Epoch
2029
Orbittype
Aten
Orbitalperiod
0.89 years (323.6 days)
Semi-majoraxis
0.922
Perihelion
0.746
Aphelion
1.10
Inclination
3.34°
Eccentricity
0.191
Post-flyby
Post-flyby
Parameter
Post-flyby
Epoch
2030
Orbittype
Apollo
Orbitalperiod
1.16 years (423.1 days)
Semi-majoraxis
1.103
Perihelion
0.895
Aphelion
1.31
Inclination
2.22°
Eccentricity
0.189
Parameter
Epoch
Orbittype
Orbitalperiod
Semi-majoraxis
Perihelion
Aphelion
Inclination
Eccentricity
Units
AU
(°)
Pre-flyby
2029
Aten
years (323.6 days)
0.922
0.746
1.10
3.34°
0.191
Post-flyby
2030
Apollo
years (423.1 days)
1.103
0.895
1.31
2.22°
0.189
Nominal(B)
Nominal(B)
PHA
Nominal(B)
Date
Minimum
Approach distance in lunar distances
Maximum
(152680) 1998 KJ9
(152680) 1998 KJ9
PHA
(152680) 1998 KJ9
Date
1914-12-31
Approach distance in lunar distances
0.606
Approach distance in lunar distances
0.604
Approach distance in lunar distances
0.608
Abs. mag(H)
19.4
Diameter (C)(m)
279–900
Ref (D)
data
(458732) 2011 MD5
(458732) 2011 MD5
PHA
(458732) 2011 MD5
Date
1918-09-17
Approach distance in lunar distances
0.911
Approach distance in lunar distances
0.909
Approach distance in lunar distances
0.913
Abs. mag(H)
17.9
Diameter (C)(m)
556–1795
Ref (D)
data
(163132) 2002 CU11
(163132) 2002 CU11
PHA
(163132) 2002 CU11
Date
1925-08-30
Approach distance in lunar distances
0.903
Approach distance in lunar distances
0.901
Approach distance in lunar distances
0.905
Abs. mag(H)
18.5
Diameter (C)(m)
443–477
Ref (D)
data
69230 Hermes
69230 Hermes
PHA
69230 Hermes
Date
1937-10-30
Approach distance in lunar distances
1.926
Approach distance in lunar distances
1.926
Approach distance in lunar distances
1.927
Abs. mag(H)
17.5
Diameter (C)(m)
700-900
Ref (D)
data
69230 Hermes
69230 Hermes
PHA
69230 Hermes
Date
1942-04-26
Approach distance in lunar distances
1.651
Approach distance in lunar distances
1.651
Approach distance in lunar distances
1.651
Abs. mag(H)
17.5
Diameter (C)(m)
700-900
Ref (D)
data
2017 NM6
2017 NM6
PHA
2017 NM6
Date
1959-07-12
Approach distance in lunar distances
1.89
Approach distance in lunar distances
1.846
Approach distance in lunar distances
1.934
Abs. mag(H)
18.8
Diameter (C)(m)
580–1300
Ref (D)
data
(27002) 1998 DV9
(27002) 1998 DV9
PHA
(27002) 1998 DV9
Date
1975-01-31
Approach distance in lunar distances
1.762
Approach distance in lunar distances
1.761
Approach distance in lunar distances
1.762
Abs. mag(H)
18.1
Diameter (C)(m)
507–1637
Ref (D)
data
2002 NY40
2002 NY40
PHA
2002 NY40
Date
2002-08-18
Approach distance in lunar distances
1.371
Approach distance in lunar distances
1.371
Approach distance in lunar distances
1.371
Abs. mag(H)
19.0
Diameter (C)(m)
335–1082
Ref (D)
data
2004 XP14
2004 XP14
PHA
2004 XP14
Date
2006-07-03
Approach distance in lunar distances
1.125
Approach distance in lunar distances
1.125
Approach distance in lunar distances
1.125
Abs. mag(H)
19.3
Diameter (C)(m)
292–942
Ref (D)
data
2015 TB145
2015 TB145
PHA
2015 TB145
Date
2015-10-31
Approach distance in lunar distances
1.266
Approach distance in lunar distances
1.266
Approach distance in lunar distances
1.266
Abs. mag(H)
20.0
Diameter (C)(m)
620-690
Ref (D)
data
(137108) 1999 AN10
(137108) 1999 AN10
PHA
(137108) 1999 AN10
Date
2027-08-07
Approach distance in lunar distances
1.014
Approach distance in lunar distances
1.010
Approach distance in lunar distances
1.019
Abs. mag(H)
17.9
Diameter (C)(m)
556–1793
Ref (D)
data
(153814) 2001 WN5
(153814) 2001 WN5
PHA
(153814) 2001 WN5
Date
2028-06-26
Approach distance in lunar distances
0.647
Approach distance in lunar distances
0.647
Approach distance in lunar distances
0.647
Abs. mag(H)
18.2
Diameter (C)(m)
921–943
Ref (D)
data
99942 Apophis
99942 Apophis
PHA
99942 Apophis
Date
2029-04-13
Approach distance in lunar distances
0.0981
Approach distance in lunar distances
0.0963
Approach distance in lunar distances
0.1000
Abs. mag(H)
19.7
Diameter (C)(m)
310–340
Ref (D)
data
2017 MB1
2017 MB1
PHA
2017 MB1
Date
2072-07-26
Approach distance in lunar distances
1.216
Approach distance in lunar distances
1.215
Approach distance in lunar distances
2.759
Abs. mag(H)
18.8
Diameter (C)(m)
367–1186
Ref (D)
data
2011 SM68
2011 SM68
PHA
2011 SM68
Date
2072-10-17
Approach distance in lunar distances
1.875
Approach distance in lunar distances
1.865
Approach distance in lunar distances
1.886
Abs. mag(H)
19.6
Diameter (C)(m)
254–820
Ref (D)
data
(163132) 2002 CU11
(163132) 2002 CU11
PHA
(163132) 2002 CU11
Date
2080-08-31
Approach distance in lunar distances
1.655
Approach distance in lunar distances
1.654
Approach distance in lunar distances
1.656
Abs. mag(H)
18.5
Diameter (C)(m)
443–477
Ref (D)
data
(416801) 1998 MZ
(416801) 1998 MZ
PHA
(416801) 1998 MZ
Date
2116-11-26
Approach distance in lunar distances
1.068
Approach distance in lunar distances
1.068
Approach distance in lunar distances
1.069
Abs. mag(H)
19.2
Diameter (C)(m)
305–986
Ref (D)
data
(153201) 2000 WO107
(153201) 2000 WO107
PHA
(153201) 2000 WO107
Date
2140-12-01
Approach distance in lunar distances
0.634
Approach distance in lunar distances
0.631
Approach distance in lunar distances
0.637
Abs. mag(H)
19.3
Diameter (C)(m)
427–593
Ref (D)
data
(276033) 2002 AJ129
(276033) 2002 AJ129
PHA
(276033) 2002 AJ129
Date
2172-02-08
Approach distance in lunar distances
1.783
Approach distance in lunar distances
1.775
Approach distance in lunar distances
1.792
Abs. mag(H)
18.7
Diameter (C)(m)
385–1242
Ref (D)
data
(290772) 2005 VC
(290772) 2005 VC
PHA
(290772) 2005 VC
Date
2198-05-05
Approach distance in lunar distances
1.951
Approach distance in lunar distances
1.791
Approach distance in lunar distances
2.134
Abs. mag(H)
17.6
Diameter (C)(m)
638–2061
Ref (D)
data
(A) This list includes near-Earth approaches of less than 2 lunar distances (LD) of objects with H brighter than 20.(B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)(E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches
(A) This list includes near-Earth approaches of less than 2 lunar distances (LD) of objects with H brighter than 20.(B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)(E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches
PHA
(A) This list includes near-Earth approaches of less than 2 lunar distances (LD) of objects with H brighter than 20.(B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)(E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches
PHA
Date
Approach distance in lunar distances
Abs. mag(H)
Diameter (C)(m)
Ref (D)
Nominal(B)
Minimum
Maximum
(152680) 1998 KJ9
1914-12-31
0.606
0.604
0.608
19.4
279–900
data
(458732) 2011 MD5
1918-09-17
0.911
0.909
0.913
17.9
556–1795
data
(163132) 2002 CU11
1925-08-30
0.903
0.901
0.905
18.5
443–477
data
69230 Hermes
1937-10-30
1.926
1.926
1.927
17.5
700-900
data
69230 Hermes
1942-04-26
1.651
1.651
1.651
17.5
700-900
data
2017 NM6
1959-07-12
1.89
1.846
1.934
18.8
580–1300
data
(27002) 1998 DV9
1975-01-31
1.762
1.761
1.762
18.1
507–1637
data
2002 NY40
2002-08-18
1.371
1.371
1.371
19.0
335–1082
data
2004 XP14
2006-07-03
1.125
1.125
1.125
19.3
292–942
data
2015 TB145
2015-10-31
1.266
1.266
1.266
20.0
620-690
data
(137108) 1999 AN10
2027-08-07
1.014
1.010
1.019
17.9
556–1793
data
(153814) 2001 WN5
2028-06-26
0.647
0.647
0.647
18.2
921–943
data
99942 Apophis
2029-04-13
0.0981
0.0963
0.1000
19.7
310–340
data
2017 MB1
2072-07-26
1.216
1.215
2.759
18.8
367–1186
data
2011 SM68
2072-10-17
1.875
1.865
1.886
19.6
254–820
data
(163132) 2002 CU11
2080-08-31
1.655
1.654
1.656
18.5
443–477
data
(416801) 1998 MZ
2116-11-26
1.068
1.068
1.069
19.2
305–986
data
(153201) 2000 WO107
2140-12-01
0.634
0.631
0.637
19.3
427–593
data
(276033) 2002 AJ129
2172-02-08
1.783
1.775
1.792
18.7
385–1242
data
(290772) 2005 VC
2198-05-05
1.951
1.791
2.134
17.6
638–2061
data
(A) This list includes near-Earth approaches of less than 2 lunar distances (LD) of objects with H brighter than 20.(B) Nominal geocentric distance from the center of Earth to the center of the object (Earth has a radius of approximately 6,400 km).(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)(E) Color codes: unobserved at close approach observed during close approach upcoming approaches
· Orbit › History of impact estimates
2004-12-23
2004-12-23
Date
2004-12-23
Status
The original NASA report mentioned impact chances of "around 1 in 300" in 2029, which was widely reported in the media. The actual NASA estimates at the time were 1 in 233; these resulted in a Torino scale rating of 2, the first time any asteroid had received a rating above 1.
2004-12-25
2004-12-25
Date
2004-12-25
Status
The chances were first reported as 1 in 42 (2.4%) and later that day (based on 101 observations) as 1 in 45 (2.2%). At the same time, the asteroid's estimated diameter was lowered from 440 m to 390 m and its mass from 1.2×1011 kg to 8.3×1010 kg.
2004-12-26
2004-12-26
Date
2004-12-26
Status
Based on a total of 169 observations, the impact probability was still estimated as 1 in 45 (2.2%), the estimates for diameter and mass were lowered to 380 m and 7.5×1010 kg, respectively.
2004-12-27
2004-12-27
Date
2004-12-27
Status
Based on a total of 176 observations with an observation arc of 190 days, the impact probability was raised to 1 in 37 (2.7%) with a line of variation (LOV) of only 83,000 km; diameter was increased to 390 m, and mass to 7.9×1010 kg.
2004-12-28
2004-12-28
Date
2004-12-28
Time
12:23 GMT
Status
Based on a total of 139 observations, a value of one was given on the Torino scale for 2044-04-13.29 and 2053-04-13.51.
2004-12-29
2004-12-29
Date
2004-12-29
Time
01:10 GMT
Status
The only pass rated 1 on the Torino scale was for 2053-04-13.51 based on 139 observations spanning 287.71 days (2004-Mar-15.1104 to 2004-Dec-27.8243).
19:18 GMT
19:18 GMT
Date
19:18 GMT
Time
This was still the case based upon 147 observations spanning 288.92 days (2004-Mar-15.1104 to 2004-Dec-29.02821), though the close encounters were changed and reduced to 4 in total.
2004-12-30
2004-12-30
Date
2004-12-30
Time
13:46 GMT
Status
No passes were rated above 0, based upon 157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). The most dangerous pass was rated at 1 in 7,143,000.
22:34 GMT
22:34 GMT
Date
22:34 GMT
Time
157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). One pass at 1 (Torino scale) 3 other passes.
2005-01-02
2005-01-02
Date
2005-01-02
Time
03:57 GMT
Status
Observations spanning 290.97 days (2004-Mar-15.1104 to 2004-Dec-31.07992) One pass at 1 (Torino scale) 19 other passes.
2005-01-03
2005-01-03
Date
2005-01-03
Time
14:49 GMT
Status
Observations spanning 292.72 days (2004-Mar-15.1104 to 2005-Jan-01.82787) One pass at 1 (Torino scale) 15 other passes.
2005–01
2005–01
Date
2005–01
Status
Extremely precise radar observations at Arecibo Observatory refine the orbit further and show that the April 2029 close approach will occur at only 5.7 Earth radii, approximately one-half the distance previously estimated.
2005-02-06
2005-02-06
Date
2005-02-06
Status
Apophis estimated to have a 1-in-13,000 chance of impacting in April 2036.
2005-08-07
2005-08-07
Date
2005-08-07
Status
Radar observation refines the orbit further and eliminates the possibility of an impact in 2035. Only the pass in 2036 remains at Torino scale 1 (with a 1-in-5,560 chance of impact).
2005–10
2005–10
Date
2005–10
Status
It is predicted that Apophis will pass just below the altitude of geosynchronous satellites, which are at approximately 35,900 kilometres (22,300 mi). Such a close approach by an asteroid of that size is estimated to occur every 800 years or so.
2006-05-06
2006-05-06
Date
2006-05-06
Status
Radar observation at Arecibo Observatory slightly lowered the Palermo scale rating, but the pass in 2036 remained at Torino scale 1 despite the impact probability dropping by a factor of four.
2006-08-05
2006-08-05
Date
2006-08-05
Status
Additional observations through 2006 resulted in Apophis being lowered to Torino scale 0. (The impact probability was assessed as 1 in 45,000.)
2008-04
2008-04
Date
2008-04
Status
News outlets carry the story that 13-year-old German student Nico Marquardt found a probability of 1 in 450 for a 2036 impact. This estimate was allegedly acknowledged by ESA and NASA but in an official statement, NASA denied they had made an error. The release went on to explain that since the angle of Apophis's approach to the Earth's equator means the asteroid will not travel through the belt of current equatorial geosynchronous satellites, there is currently no risk of collision; and the effect on Apophis's orbit of any such impact would be insignificant.
2009-04-29
2009-04-29
Date
2009-04-29
Status
An animation is released that shows how unmeasured physical parameters of Apophis bias the entire statistical uncertainty region. If Apophis is a retrograde rotator on the small, less-massive end of what is possible, it will be several hundred kilometres further ahead in 2029, resulting in a different change to its orbit, and then the measurement uncertainty region for 2036 will get pushed back such that the center of the distribution encounters Earth's orbit. This would result in an impact probability much higher than computed with the Standard Dynamical Model. Conversely, if Apophis is a small, less-massive prograde rotator, it arrives a bit later on April 13, 2029, and the uncertainty region for 2036 is advanced along the orbit. Only the remote tails of the probability distribution could encounter Earth, producing a negligible impact probability for 2036.
2009-10-07
2009-10-07
Date
2009-10-07
Status
Refinements to the precovery images of Apophis by the University of Hawaii's Institute for Astronomy, the 90-inch Bok Telescope, and the Arecibo Observatory have generated a refined path that reduces the odds of an April 13, 2036, impact to about 1 in 250,000.
2013-01
2013-01
Date
2013-01
Status
A statistical impact risk analysis of the data up to this point calculated that the odds of the 2036 impact at 7.07 in a billion, effectively ruling it out. The same study looked at the odds of an impact in 2068, which were calculated at 2.27 in a million. First appearance of Sentry virtual impactors that also include mid-October dates.
2013-01-09
2013-01-09
Date
2013-01-09
Status
The European Space Agency (ESA) announced that the Herschel Space Observatory made new thermal infrared observations of the asteroid as it approached Earth. The initial data shows the asteroid to be bigger than first estimated because it is now expected to be less reflective than originally thought. The Herschel Space Observatory observations increased the diameter estimate by 20% from 270 to 325 metres, which translates into a 75% increase in the estimates of the asteroid's volume or mass. Goldstone single-pixel observations of Apophis have ruled out the potential 2036 Earth impact. Apophis will then come no closer than about 23 million kilometres (14×10^6 mi)—and more likely miss us by something closer to 56 million kilometres (35×10^6 mi). The radar astrometry is more precise than was expected.
2014-10-8
2014-10-8
Date
2014-10-8
Status
The Sentry Risk Table assessed Apophis as having a 6.7-in-a-million (1-in-150,000) chance of impacting Earth in 2068, and a 9-in-a-million (1-in-110,000) cumulative chance of impacting Earth by 2105.
2020-03
2020-03
Date
2020-03
Status
By taking observations of Apophis with the Subaru Telescope in January and March 2020, as well as remeasuring older observations using the new Gaia DR2 star catalog, astronomers positively detect the Yarkovsky effect on Apophis. The semi-major axis thereby decreases by about 170 metres per year. The Yarkovsky effect is the main source of uncertainty in impact probability estimates for this asteroid.
2021-02-21
2021-02-21
Date
2021-02-21
Status
Apophis was removed from the Sentry Risk Table, as an impact in the next 100 years was finally ruled out.
2021-03-15
2021-03-15
Date
2021-03-15
Time
10:44
Status
JPL solution #207 using observations in 2020 and 2021 reduced the 3-sigma uncertainty region in the 2029 approach distance from ±700 km to about ±3 km. The June 2021 solution showed the Earth approach on March 27, 2036, will be no closer than 0.30889 AU (46.209 million km; 28.713 million mi; 120.21 LD).
2024-06-25
2024-06-25
Date
2024-06-25
Status
JPL solution #220 includes observations through 2022-April-09.
Date
Time
Status
2004-12-23
The original NASA report mentioned impact chances of "around 1 in 300" in 2029, which was widely reported in the media. The actual NASA estimates at the time were 1 in 233; these resulted in a Torino scale rating of 2, the first time any asteroid had received a rating above 1.
Later that day, based on a total of 64 observations, the estimates were changed to 1 in 62 (1.6%), resulting in an update to the initial report and an upgrade to a Torino scale rating of 4.
2004-12-25
The chances were first reported as 1 in 42 (2.4%) and later that day (based on 101 observations) as 1 in 45 (2.2%). At the same time, the asteroid's estimated diameter was lowered from 440 m to 390 m and its mass from 1.2×1011 kg to 8.3×1010 kg.
2004-12-26
Based on a total of 169 observations, the impact probability was still estimated as 1 in 45 (2.2%), the estimates for diameter and mass were lowered to 380 m and 7.5×1010 kg, respectively.
2004-12-27
Based on a total of 176 observations with an observation arc of 190 days, the impact probability was raised to 1 in 37 (2.7%) with a line of variation (LOV) of only 83,000 km; diameter was increased to 390 m, and mass to 7.9×1010 kg.
Later that afternoon, a precovery increased the span of observations to 287 days, which eliminated the 2029 impact threat. The cumulative impact probability was estimated to be around 0.004%, a risk lower than that of asteroid 2004 VD17, which once again became (temporarily) the greatest-risk object. A 2053 approach to Earth still posed a minor risk of impact, and Apophis was still rated at level one on the Torino scale for this orbit.
2004-12-28
12:23 GMT
Based on a total of 139 observations, a value of one was given on the Torino scale for 2044-04-13.29 and 2053-04-13.51.
2004-12-29
01:10 GMT
The only pass rated 1 on the Torino scale was for 2053-04-13.51 based on 139 observations spanning 287.71 days (2004-Mar-15.1104 to 2004-Dec-27.8243).
19:18 GMT
This was still the case based upon 147 observations spanning 288.92 days (2004-Mar-15.1104 to 2004-Dec-29.02821), though the close encounters were changed and reduced to 4 in total.
2004-12-30
13:46 GMT
No passes were rated above 0, based upon 157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). The most dangerous pass was rated at 1 in 7,143,000.
22:34 GMT
157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). One pass at 1 (Torino scale) 3 other passes.
2005-01-02
03:57 GMT
Observations spanning 290.97 days (2004-Mar-15.1104 to 2004-Dec-31.07992) One pass at 1 (Torino scale) 19 other passes.
2005-01-03
14:49 GMT
Observations spanning 292.72 days (2004-Mar-15.1104 to 2005-Jan-01.82787) One pass at 1 (Torino scale) 15 other passes.
2005–01
Extremely precise radar observations at Arecibo Observatory refine the orbit further and show that the April 2029 close approach will occur at only 5.7 Earth radii, approximately one-half the distance previously estimated.
2005-02-06
Apophis estimated to have a 1-in-13,000 chance of impacting in April 2036.
2005-08-07
Radar observation refines the orbit further and eliminates the possibility of an impact in 2035. Only the pass in 2036 remains at Torino scale 1 (with a 1-in-5,560 chance of impact).
2005–10
It is predicted that Apophis will pass just below the altitude of geosynchronous satellites, which are at approximately 35,900 kilometres (22,300 mi). Such a close approach by an asteroid of that size is estimated to occur every 800 years or so.
2006-05-06
Radar observation at Arecibo Observatory slightly lowered the Palermo scale rating, but the pass in 2036 remained at Torino scale 1 despite the impact probability dropping by a factor of four.
2006-08-05
Additional observations through 2006 resulted in Apophis being lowered to Torino scale 0. (The impact probability was assessed as 1 in 45,000.)
2008-04
News outlets carry the story that 13-year-old German student Nico Marquardt found a probability of 1 in 450 for a 2036 impact. This estimate was allegedly acknowledged by ESA and NASA but in an official statement, NASA denied they had made an error. The release went on to explain that since the angle of Apophis's approach to the Earth's equator means the asteroid will not travel through the belt of current equatorial geosynchronous satellites, there is currently no risk of collision; and the effect on Apophis's orbit of any such impact would be insignificant.
2009-04-29
An animation is released that shows how unmeasured physical parameters of Apophis bias the entire statistical uncertainty region. If Apophis is a retrograde rotator on the small, less-massive end of what is possible, it will be several hundred kilometres further ahead in 2029, resulting in a different change to its orbit, and then the measurement uncertainty region for 2036 will get pushed back such that the center of the distribution encounters Earth's orbit. This would result in an impact probability much higher than computed with the Standard Dynamical Model. Conversely, if Apophis is a small, less-massive prograde rotator, it arrives a bit later on April 13, 2029, and the uncertainty region for 2036 is advanced along the orbit. Only the remote tails of the probability distribution could encounter Earth, producing a negligible impact probability for 2036.
2009-10-07
Refinements to the precovery images of Apophis by the University of Hawaii's Institute for Astronomy, the 90-inch Bok Telescope, and the Arecibo Observatory have generated a refined path that reduces the odds of an April 13, 2036, impact to about 1 in 250,000.
Criticism of older published impact probabilities rests on the fact that important physical parameters such as mass and spin that affect its precise trajectory had not yet been accurately measured and hence there were no associated probability distributions. The Standard Dynamical Model used for making predictions simplifies calculations by assuming Earth is a point mass. This could lead to a prediction error of up to 2.9 Earth radii for the 2036 approach, necessitating the consideration of Earth's oblateness during the 2029 passage for accurately forecasting the potential impact. Additional factors that could greatly influence the predicted motion in ways that depend on unknown details, were the spin of the asteroid, its precise mass, the way it reflects and absorbs sunlight, radiates heat, and the gravitational pull of other asteroids passing nearby. Small uncertainties in the masses and positions of the planets and Sun could cause up to 23 Earth radii of prediction error for Apophis by 2036.
2013-01
A statistical impact risk analysis of the data up to this point calculated that the odds of the 2036 impact at 7.07 in a billion, effectively ruling it out. The same study looked at the odds of an impact in 2068, which were calculated at 2.27 in a million. First appearance of Sentry virtual impactors that also include mid-October dates.
2013-01-09
The European Space Agency (ESA) announced that the Herschel Space Observatory made new thermal infrared observations of the asteroid as it approached Earth. The initial data shows the asteroid to be bigger than first estimated because it is now expected to be less reflective than originally thought. The Herschel Space Observatory observations increased the diameter estimate by 20% from 270 to 325 metres, which translates into a 75% increase in the estimates of the asteroid's volume or mass. Goldstone single-pixel observations of Apophis have ruled out the potential 2036 Earth impact. Apophis will then come no closer than about 23 million kilometres (14×10^6 mi)—and more likely miss us by something closer to 56 million kilometres (35×10^6 mi). The radar astrometry is more precise than was expected.
2014-10-8
The Sentry Risk Table assessed Apophis as having a 6.7-in-a-million (1-in-150,000) chance of impacting Earth in 2068, and a 9-in-a-million (1-in-110,000) cumulative chance of impacting Earth by 2105.
2020-03
By taking observations of Apophis with the Subaru Telescope in January and March 2020, as well as remeasuring older observations using the new Gaia DR2 star catalog, astronomers positively detect the Yarkovsky effect on Apophis. The semi-major axis thereby decreases by about 170 metres per year. The Yarkovsky effect is the main source of uncertainty in impact probability estimates for this asteroid.
2021-02-21
Apophis was removed from the Sentry Risk Table, as an impact in the next 100 years was finally ruled out.
2021-03-15
10:44
JPL solution using observations in 2020 and 2021 reduced the 3-sigma uncertainty region in the 2029 approach distance from ±700 km to about ±3 km. The June 2021 solution showed the Earth approach on March 27, 2036, will be no closer than 0.30889 AU (46.209 million km; 28.713 million mi; 120.21 LD).
2024-06-25
JPL solution includes observations through 2022-April-09.
· External links
Preceded by(153814) 2001 WN5
Large NEO Earth close approach(inside the orbit of the Moon) April 13, 2029
Succeeded by2012 UE34

References

  1. Like all orbital elements, the E-MOID changes depending on the epoch it is defined at. At epoch May 2025, the E-MOID is
  2. Of the six asteroids with a higher Palermo scale rating than Apophis at the time: (29075) 1950 DA and 101955 Bennu canno
  3. This is normal for classical names in which the penultimate syllable is short.
  4. The minimum possible Earth approach between April 5–20, 2116 is 0.00102 AU (153 thousand km). "JPL Horizons" gives 13 mi
  5. "JPL Horizons" gives 42 million km for 3σ
  6. On January 8, 2022 Venus was even closer to Earth at 0.2658 AU (39.76 million km; 24.71 million mi; 103.4 LD).
  7. Using the March 9, 2021, solution, JPL gave the strength of the Yarkovsky effect as A
  8. Mannocchi et al. give possible launch dates of November–December 2026, April–May 2027, September–November 2027, or March
  9. "JPL Small-Body Database Browser: 99942 Apophis (2004 MN4)"
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  10. Icarus
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  13. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology
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    https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%272029-4-1%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20days%27&QUANTITIES=%2718%2019%2020%2031
  62. According to this JPL Horizons run.
    https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%272029-4-1%2021:46%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20days%27&QUANTITIES=22
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