Asteroids

99942 Apophis help

Last update: 2025-07-29 02:36 UTC

Orbital Properties

Epoch

60800.0

MJD

Orbit type

Aten

Perihelion (q)

0.746

Aphelion (Q)

1.099

Eccentricity (e)

0.191

Inclination (i)

3.3

deg

Orbit period (P)

323.6

Earth MOID

0.00004

U parameter

0.0

A₂

-29.0

10^-15au/days²

Next Earth close approach

Date

2029-04-13

Nominal distance (from Earth center)

0.00025

38014

Maximum Brightness

3.1

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

18.9

mag

Diameter

375

Taxonomic type

Scomp

Rotation period (T)

30.56

Discovery Information

Discovery Date

2004-06-19

Observatory

Kitt Peak

ORBIT VISUALISATION TOOLS

External links

Proper elements

Epoch

Near present day

Near middle of observation arc

Orbit properties

Epoch
Semimajor Axis
Eccentricity (e)
Inclination (i)
Long. of Ascending Node (Ω)
Arg. of Perihelion (ω)
Mean Anomaly (M)
Perihelion distance
Aphelion distance
Asc. Node-Earth Sep.
Desc. Node-Earth Sep.
MOID
Orbit Period
U parameter

Value

1-sigma variation

Unit

Epoch

Value

60800.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

0.922382

1-sigma variation

1.328E-10

Unit

Eccentricity (e)

Value

0.191131

1-sigma variation

1.394E-9

Unit

Inclination (i)

Value

3.3410

1-sigma variation

1.552E-7

Unit

Long. of Ascending Node (Ω)

Value

203.9029

1-sigma variation

7.589E-6

Unit

Arg. of Perihelion (ω)

Value

126.6743

1-sigma variation

8.155E-6

Unit

Mean Anomaly (M)

Value

90.28033

1-sigma variation

9.709E-7

Unit

Perihelion distance

Value

0.746087

1-sigma variation

Unit

Aphelion distance

Value

1.098678

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.000130

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.198741

1-sigma variation

Unit

MOID

Value

0.000038

1-sigma variation

Unit

Orbit Period

Value

323.5674

1-sigma variation

Unit

U parameter

Value

0.0

1-sigma variation

Unit

A₂

Value

-29.00108

1-sigma variation

0.23232

Unit

10^-15au/days²

Covariance Matrix

	a	e	i	Ω	ω	M	A₂
a	1.76440E-20	-1.50996E-19	-1.24479E-17	4.84859E-16	-5.98215E-16	9.30591E-17	2.88203E-11
e	-1.50996E-19	1.94338E-18	6.72771E-17	-1.90288E-15	3.07727E-15	-8.65268E-16	-1.85629E-10
i	-1.24479E-17	6.72771E-17	2.40928E-14	-1.11680E-12	1.22077E-12	-1.35550E-13	-2.22116E-8
Ω	4.84859E-16	-1.90288E-15	-1.11680E-12	5.75911E-11	-6.15908E-11	5.97294E-12	9.62100E-7
ω	-5.98215E-16	3.07727E-15	1.22077E-12	-6.15908E-11	6.64967E-11	-6.80648E-12	-1.12126E-6
M	9.30591E-17	-8.65268E-16	-1.35550E-13	5.97294E-12	-6.80648E-12	9.42625E-13	1.37665E-7
A₂	2.88203E-11	-1.85629E-10	-2.22116E-8	9.62100E-7	-1.12126E-6	1.37665E-7	5.39730E-2

Date of computation: 2025-07-29 02:36 UTC

Note: The ASCII file is in a format suitable for Orbfit input.

Download ASCII file:

Physical properties

Rotation Period
Quality
Amplitude
Rotation Direction
Spinvector L
Spinvector B

Rotational properties

Value

Unit

Source

Rotation Period

Value

30.56

Unit

Source

[6]

Quality

Value

Unit

Source

[6]

Amplitude

Value

1.0

Unit

mag

Source

[6]

Rotation Direction

Value

RETRO

Unit

Source

[1]

Spinvector L

Value

250

Unit

Source

[1]

Spinvector B

Value

-75

Unit

Source

[1]

Taxonomy
Taxonomy (all)

Taxonomy

Value

Unit

Source

Taxonomy

Value

Scomp

S/Sq

Unit

Source

[2]

[3]

Taxonomy (all)

Value

Sq,Scomp

Unit

Source

[4]

[5]

Absolute Magnitude (H)
Slope Parameter (G)

H / G

Value

Unit

Source

Absolute Magnitude (H)

Value

19.09

18.892

Unit

mag

Source

[7]

[8]

Slope Parameter (G)

Value

0.24

0.15**

Unit

mag

Source

[1]

[8]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.285

Unit

Source

[10]

Diameter

Value

375

Unit

Source

[9]

Color Index Information

Color Index Information

Value

Unit

Source

Color Index Information

Value

0.846

0.362

0.451

Unit

B-V

R-I

V-R

Source

[11]

Sightings

Sightings

Value

Unit

Source

Sightings

Value

Radar R

Visual S

Unit

Source

[12]

[13]

Download this part as:

Sources

No.	Name	Additional
[1]	EARN	1.) Pravec, P. et al (2014) Icarus 233,48-60. (The tumbling spin state of (99942) Apophis)
[2]	EARN	1.) Michaël Marsset et al 2022 AJ 163 165
[3]	EARN	1.) Perna, D. et al. (2016) Astron. J. 151, 11(14p). (GRASPING THE NATURE OF POTENTIALLY HAZARDOUS ASTEROIDS) (spectra of 14 PHAs)
[4]	EARN	Earth Asteroids Research Node: https://earn.dlr.de
[5]	EARN	1.) Binzel, R.P. et al. (2009) Icarus 200, 480-485. (Spectral properties and composition of potentially hazardous Asteroid (99942) Apophis) 2.) DeMeo, F.E. et al. (2014) Icarus 227, 112-122. (Mars encounters cause fresh surfaces on some near-Earth asteroids) (contains taxonomic classification of 249 NEAs) 3.) Perna, D. et al. (2016) Astron. J. 151, 11(14p). (GRASPING THE NATURE OF POTENTIALLY HAZARDOUS ASTEROIDS) (spectra of 14 PHAs)
[6]	EARN	1.) Pravec, P. et al (2014) Icarus 233,48-60. (The tumbling spin state of (99942) Apophis) 2.) R. Behrend Courbes des lumiere, Observatoire de Geneve website 3.) Oey, J. (2014) MPB 41, 276-280. (LIGHTCURVE ANALYSIS OF ASTEROIDS FROM BLUE MOUNTAINS OBSERVATORY IN 2013) (99942, 163364,285263)
[7]	EARN	1.) Pravec, P. et al (2014) Icarus 233,48-60. (The tumbling spin state of (99942) Apophis) 2.) Delbo, M. et al. (2007) Icarus 188,266-269. (Albedo and size determination of potentially hazardous asteroids: (99942) Apophis)
[8]	ESA Aegis	ESA orbit determination and impact monitoring system
[9]	EARN	1.) Licandro, J. et al. (2016) Astron. Astrophys. 585, A10. (GTC/CanariCam observations of (99942) Apophis) 2.) Mueller, T.G. et al. (2014) Astron. Astrophys. 566, A22. (Thermal Infrared Observations of Asteroid (99942) Apophis with Herschel) 3.) Mueller, T. et al. (2013) href="http://www.esa.int/Our_Activities/Space_Science/Herschel_intercepts_asteroid_Apophis"> New Size and Albedo for Apophis from IR Data obtained with Herschel Space Telescope 4.) Delbo, M. et al. (2007) Icarus 188,266-269. (Albedo and size determination of potentially hazardous asteroids: (99942) Apophis)
[10]	EARN	1.) Licandro, J. et al. (2016) Astron. Astrophys. 585, A10. (GTC/CanariCam observations of (99942) Apophis) 2.) Mueller, T.G. et al. (2014) Astron. Astrophys. 566, A22. (Thermal Infrared Observations of Asteroid (99942) Apophis with Herschel) 3.) Mueller, T. et al. (2013) href="http://www.esa.int/Our_Activities/Space_Science/Herschel_intercepts_asteroid_Apophis"> New Size and Albedo for Apophis from IR Data obtained with Herschel Space Telescope 4.) Delbo, M. et al. (2007) Icarus 188,266-269. (Albedo and size determination of potentially hazardous asteroids: (99942) Apophis) 5.) Licandro, J. et al. (2016) Astron. Astrophys. 585, A10. (GTC/CanariCam observations of (99942) Apophis)
[11]	EARN	1.) Lin, C-H. et al. (2018) P&SS 152, 116-135. (Photometric survey and taxonomic identifications of 92 near-Earth asteroids)
[12]	EARN	1.) href="http://echo.jpl.nasa.gov/asteroids/index.html">JPL's NEO Radar Detection Program Webpage 2.) Ostro, S.J. et al. (2005) I.A.U. Circ. HREF="http://www.cbat.eps.harvard.edu/iauc/08400/08477.html"> 8477. (2004 MN_4) Radar observations) 3.) Giorgini, J.D. et al. (2005) I.A.U. Circ. HREF="http://www.cbat.eps.harvard.edu/iauc/08500/08593.html"> 8593. (99942 Apophis) (radar observations and orbital improvement) 4.) Benner, L.A.M. et al. (2006) I.A.U. Circ. HREF="http://www.cbat.eps.harvard.edu/iauc/08700/08711.html"> 8711. ((99942) APOPHIS) (radar observations and orbital improvement)
[13]	EARN	1.) Binzel, R.P. et al. (2004) Meteorit. Planet. Sci. 39, 351-366. (Dynamical and compositional assessment of near-Earth object mission targets) (new spectra and taxonomy of 22 NEOs) 2.) Binzel, R.P. et al. (2006) LPSC 37, 1491. (The MIT-Hawaii-IRTF joint campaign for NEO spectral reconnaissance.) 3.) Binzel, R.P. et al. href="http://smass.mit.edu/minus.html"> Webpage 4.) Binzel, R.P. et al. (2009) Icarus 200, 480-485. (Spectral properties and composition of potentially hazardous Asteroid (99942) Apophis) 5.) Perna, D. et al. (2016) Astron. J. 151, 11(14p). (GRASPING THE NATURE OF POTENTIALLY HAZARDOUS ASTEROIDS) (spectra of 14 PHAs)

Observational Information

Arc Length
Unobserved
Normalized RMS of residuals

Arc Information

Value

Unit

Source

Arc Length

Value

6599

Unit

Source

[1]

Unobserved

Value

1221

Unit

Source

[1]

Normalized RMS of residuals

Value

0.302422

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2004-03-15.10789

Unit

Source

[2]

Last Observation

Value

2022-04-09.361967

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

9528 (31)

Unit

Source

[1]

Radar Summary

First Observation
Last Observation
Delay (Discarded)
Doppler (Discarded)
Total Optical Observations (Discarded)

Radar

Value

Unit

Source

First Observation

Value

2005-01-27

Unit

Source

[3]

Last Observation

Value

2021-03-11

Unit

Source

[3]

Delay (Discarded)

Value

20 (0)

Unit

Source

[1]

Doppler (Discarded)

Value

30 (0)

Unit

Source

[1]

Total Radar Observations (Discarded)

Value

50 (0)

Unit

Source

[1]

Note: The ASCII file is in a format suitable for Orbfit input.

Sources

No.	Name	Additional
[1]	ESA Aegis	ESA orbit determination and impact monitoring system
[2]	MPC	Minor Planet Center: https://www.minorplanetcenter.net
[3]	JPL Radar Observations	Jet Propulsion Laboratory: https://ssd.jpl.nasa.gov/dat/radar_data_ast.txt

Computation parameters

As seen from:

Initial Date: *

Final Date: *

Output option:

One line per time step

Time step:*

* - these fields are required

Close Approaches for 99942 Apophis from 1950 to 2125

Body	Date in UTC	Time uncert. in min	Nominal distance in au	Min. possible distance in au	Distance uncert. in au
EARTH	1957-04-01 03:20	< 1 min	0.0753956	0.0753945	0.0000004
EARTH	1964-10-24 21:45	< 1 min	0.1876924	0.1876919	0.0000002
EARTH	1965-02-11 12:15	< 1 min	0.1258368	0.1258368	0.0000000
EARTH	1972-12-24 11:52	< 1 min	0.0792379	0.0792374	0.0000002
EARTH	1980-12-18 01:51	< 1 s	0.0721269	0.0721266	0.0000001
EARTH	1982-04-11 12:16	< 1 s	0.1795311	0.1795307	0.0000001
EARTH	1990-04-14 20:44	< 1 s	0.0329292	0.0329291	0.0000001
EARTH	1998-04-14 19:45	< 1 s	0.0243871	0.0243871	0.0000000
EARTH	2004-12-21 09:24	< 1 s	0.0963839	0.0963838	0.0000000
EARTH	2013-01-09 11:42	< 1 s	0.0966611	0.0966611	0.0000000
EARTH	2021-03-06 01:13	< 1 s	0.1126514	0.1126514	0.0000000
EARTH	2029-04-13 21:45	< 1 s	0.0002541	0.0002541	0.0000000
EARTH	2044-08-23 14:16	463.1	0.0813842	0.0797645	0.0005402
EARTH	2051-04-19 19:27	185.5	0.0401743	0.0381863	0.0006627
EARTH	2066-09-16 09:01	203.2	0.0744756	0.0665886	0.0026444
EARTH	2073-07-29 05:37	> 1 d	0.1109267	0.1085948	0.0007776
EARTH	2080-05-09 23:40	781.5	0.0879309	0.0859351	0.0006653
EARTH	2087-04-07 09:41	56.9	0.0971589	0.0956396	0.0005064
EARTH	2102-09-11 07:06	441.9	0.0254213	0.0227177	0.0013374
EARTH	2109-03-18 19:44	> 1 w	0.1823733	0.1461771	0.0120934
EARTH	2109-06-11 06:31	> 1 w	0.1210524	0.1113583	0.0032673
EARTH	2116-04-08 07:37	> 1 d	0.0812486	0.0013273	0.0266722
EARTH	2124-09-21 03:40	1098.6	0.1480768	0.1019205	0.0154639

Download as:

Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
242.77024665	100.80312082	0.00003808	MINIMUM
107.69099638	346.42243140	0.05216023	MINIMUM
173.21000068	42.21718913	0.12125008	SADDLE
353.96245092	221.90463765	0.26873727	SADDLE
355.35259354	43.59846363	1.73413830	SADDLE
177.07054435	225.35562456	2.10915917	MAXIMUM

Download:

MOID Plots

Click on the images to zoom-in and zoom-out