Solar System
Dynamics
Group 		(99942) Apophis
2004 MN4




This project was supported by the Polish Ministry of Science and Higher Education — grant 4T 12E 039 20, which was realized in the years 2005–2009. The last update of this page was implemented here in 2013.

Apophis was discovered on June 19, 2004, by Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi of the NASA-founded University of Hawaii Asteroid Survey from Kitt Peak National Observatory in Arizona.
Precovery observations from March 15, 2004 were identified on December 27, 2004.
Observations from the arc: June—December 2004 indicated a probability that Apophis would strike the Earth in 2029. The present observations eliminated that probability, however during the 2029 close encounter with Earth, Apophis would pass through a 'gravitational keyhole' — a well-defined region in space no more than about few hundred meters across — that would put it on a collision course with Earth later.

At the beginning of 2011 the new data was taken after more than three years of break.
Apophis passed Earth within about 0.1 AU in January 2013.
Previous estimates of Apophis size were 270±60 m (Delbò M., Cellino A., and Tedesco E. F., 2007, Icarus, 188, 266).
The new Herschel observations give 325±15 m.
July 2013:
we confirm our previous predictions (given in 2011; on this page as 'older results') that probabilities of impacts in 2036 and 2037 are reduced effectively to nil. On the basis of these 4121 observations we derived a keyhole of 6.0532±0.0045 REarth for the close encounter with the Earth on 2029 April 13.91. Our new osculating orbit is given below.

To orbit determination we used all 4121 astrometric data available at NeoDys Page that cover the period of 2004 03 15 – 2013 05 27. We constructed so called normal places, i.e. more than two observations of the same day were replaced by one average comet position. Finally we had 262 comet positions including 210 normal places. Then, we divided the Apophis data into seven subintervals according to the data structure (we usually put the boudaries of data subintervals in the gaps in the measurements) and next the entire data set were handled by the iterative procedure of selection and weighting simultaneously with the osculating orbit determination.

Current result (data treatment: normal places and data weighting)

Number of original observations: 4121
Arc : 2004 03 15 - 2013 05 27
Nominal rms: 0″.35

Osculating orbit at the Epoch of 20130538 TT (Equinox: J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
±		 20130528
  		0.9221304537
0.0000000012		 0.1911426875
0.0000000420 		3.3304557
0.0000017 		204.2231326
0.0000516 		126.4440710
0.0000503 		280.0057645
0.0000146 		0″.35
 

Osculating orbit at the Epoch of 20290305 TT (Equinox: J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
±		 20290305
  		0.9223315606
0.0000000010		 0.1912154080
0.0000000421 		3.3420247
0.0000017 		203.8626659
0.0000515 		126.6985628
0.0000501 		207.9735452
0.0000208 		0″.35
 


Oldest results based on considerably shorter arcs



Older results
In the Apophis case (case of low probability of asteroid collision with Earth) the apprioprate selection and weighting of the data are crucial for the impact investigation. We discussed this problem in details in the paper:
How selection and weighting of astrometric observations influence the impact probability. The case of asteroid (99942) Apophis
(Królikowska M., Sitarski G. and Sołtan A.M., 2009, MNRAS )
In 2010 two popular articles describing our results are published in polish magazines:
270 metrów strachu (magazine: Wiedza i Życie)
Klucz do Apophis (The Magazine of the Polish Academy of Sciences: Academia), english version: The Key to Apophis


-->
Distributions of the minimum distance of the asteroid Apophis from the centre of Earth in 2029 04 13 derived for the samples of 15000 virtual orbits.
The minimum-distance histograms for shorter arc ( Model E in Królikowska, Sitarski & Sołtan, 2009, MNRAS) is shown with a blue solid line, for the model based on longer arc is shown with a red solid line and filled histogram (see below),
while the model_2011 based on 1483 observations (2004 03 15 - 2011 03 14, see older results ) is shown by a magenta filled histogram. According to presented results it seems that the additional observations taken in 2011 reduce the asteroid's impact probabilities (in: 2036, 2037, 2044, 2054, 2056, 2059, 2076) effectively to nil (see figure and impact orbits given below)

Thin dotted vertical lines representing the position of nominal orbits derived for Model E , for red model , and for the model_2011 are shown with a blue, red and magenta ink, respectively.

Distances for selected impacts at dates indicated by labels are presented by black vertical lines.

Impact orbit in 2076 is connected with very close encounter with Earth in 2051. Thus, the keyhole in 2029 is extremely narrow for the impact in 2076.
March 25, 2011; credits: Sitarski & Królikowska , Space Research Centre PAS
red model see Królikowska M. and Sitarski G. arXiv e-print: Note about the impact possibilities of asteroid (99942) Apophis

Results derived in 2012 (weighted observations)

Number of original observations: 1518
Arc : 2004 03 15 - 2012 05 08
Nominal rms: 0″.20 (3018 residuals)

Possible collisions in: 2036, 2037, 2044, 2046, 2054, 2055, 2056, 2059, 2076





Year: 2036


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20360407 		0.922263089
23.39
1.108425263 		0.191058800
-28.18
0.191388652 		3.3313299
-7.20
2.1710663 		204.4601578
3.06
203.4807440 		126.3953486
-2.52
70.3084804 		84.7865779
-9.22
303.9199150 		0″.23

 

Impact date: 2036 04 13.366 (UT)   Vimpact= 12.914 km/sec   Ψimpact = 31°.49  

dev/σ
Deviation from the nominal orbit parameter divided by the respective uncertainty.
Vimpact
The velocity of the asteroid relative to the Earth at the moment of impact.
Ψimpact
The impact angle is measured from the vertical axis that goes through the impact point. Thus, the impact angle is 0 degrees for a vertical impact.
rms
Root mean square for the derived impact orbit.





Year: 2037


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20370407 		0.922263248
-26.86
1.093191964 		0.191058345
5.42
0.186818609 		3.3313233
1.57
2.3248608 		204.4598383
25.10
203.4807051 		126.3956779
-26.80
73.9648356 		84.7864392
20.00
300.0418976 		0″.28

 

Impact date: 2037 04 13.640(UT)   Vimpact= 12.883 km/sec   Ψimpact = 39°.60  



Year: 2044


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20440407 		0.922263249
-27.18
1.108351655 		0.191058273
10.74
0.190962846 		3.3313260
-2.02
2.2963983 		204.4599727
15.83
203.2835273 		126.3955185
-15.05
70.2655109 		84.7864730
12.88
304.0443749 		0″.26

 

Impact date: 2044 04 13.260(UT)   Vimpact= 12.900 km/sec   Ψimpact = 56°.03  



Year: 2046


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20460407 		0.922263320
-47.63
1.086470920 		0.191058015
28.57
0.184791149 		3.3313150
12.56
2.4170949 		204.4604322
-15.75
202.9716579 		126.3951506
11.99
75.4319576 		84.7863472
38.66
298.7128495 		0″.28

 

Impact date: 2046 04 13.336(UT)   Vimpact= 12.761 km/sec   Ψimpact = 3°.95  



Year: 2054


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20540407 		0.922263255
-29.08
1.086722366 		0.191058197
16.35
0.185182832 		3.3313212
4.36
2.3527613 		204.4601565
3.15
203.0276175 		126.3953852
-5.22
75.3931868 		84.7864267
22.63
298.6950620 		0″.24

 

Impact date: 2054 04 13.397(UT)   Vimpact= 12.540 km/sec   Ψimpact = 36°.64  



Year: 2055


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20550407 		0.922263322
-50.25
1.082023691 		0.191057966
33.40
0.183918494 		3.3313189
7.41
2.4075413 		204.4602070
-0.33
203.0562387 		126.3953508
-2.68
76.6258724 		84.7863627
36.11
297.2039796 		0″.28

 

Impact date: 2055 04 13.726(UT)   Vimpact= 12.743 km/sec   Ψimpact = 8°.95  



Year: 2056


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20560407 		0.922263252
-28.13
1.076905864 		0.191058221
14.58
0.183014100 		3.3313212
4.36
2.3501801 		204.4600912
7.65
203.1436077 		126.3954481
-9.85
78.1865523 		84.7864263
22.71
296.2756880 		0″.24

 

Impact date: 2056 04 13.187(UT)   Vimpact= 13.047 km/sec   Ψimpact = 43°.13  



Year: 2059


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20590407 		0.922263252
-28.13
1.102586438 		0.191058179
17.68
0.189249766 		3.3313198
6.22
2.3137198 		204.4601807
1.48
203.0819267 		126.3953682
-3.96
71.6561664 		84.7864285
22.25
302.1232175 		0″.23

 

Impact date: 2059 04 13.950 (UT)   Vimpact= 12.813 km/sec   Ψimpact = 74°.57  



Year: 2076


Impact orbit for two dates (equ. J2000)

Epoch [TT] a [AU] e i [deg] Ω [deg] ω [deg] M [deg] rms
 
dev/σ
 		 20060922

20760407 		0.922263146
5.54
1.086675424 		0.191058604
-13.75
0.185403406 		3.3313282
-4.84
2.2686612 		204.4601380
4.36
202.6213668 		126.3953735
-4.30
75.4858831 		84.7865288
1.00
299.3072400 		0″.22

 

Impact date: 2076 04 12.693(UT) (UT)   Vimpact= 12.638 km/sec   Ψimpact = 18°.25  

External links:

2004 MN4 page (NASA JPL) and Impact Risk page NEO Program (NASA JPL)
2004 MN4 page and Impact Risk page at the NEO Dynamic Site (NEODyS)





Solar System Dynamics & Planetology Group, 2008. All rights reserved