Asteroids

2021WR4 help

Last update: 2025-09-10 00:30 UTC

Orbital Properties

Epoch

61000.0

MJD

Orbit type

Apollo

Perihelion (q)

0.959

Aphelion (Q)

1.602

Eccentricity (e)

0.251

Inclination (i)

0.4

deg

Orbit period (P)

529.3

Earth MOID

0.00111

U parameter

6.3

Next Earth close approach

Date

2035-02-20

Nominal distance (from Earth center)

0.12942

19361490

Maximum Brightness

28.5

mag

Risk

Object is in risk list

Physical Properties

Absolute Magnitude (H)

30.3

mag

Diameter

2.3 - 5*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-11-29

Observatory

Mt. Lemmon Survey

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

61000.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

1.280514

1-sigma variation

0.000078

Unit

Eccentricity (e)

Value

0.251354

1-sigma variation

0.000049

Unit

Inclination (i)

Value

0.4043

1-sigma variation

0.0001

Unit

Long. of Ascending Node (Ω)

Value

61.6041

1-sigma variation

0.0016

Unit

Arg. of Perihelion (ω)

Value

39.1896

1-sigma variation

0.0030

Unit

Mean Anomaly (M)

Value

248.05756

1-sigma variation

0.08864

Unit

Perihelion distance

Value

0.958652

1-sigma variation

Unit

Aphelion distance

Value

1.602376

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.017504

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

0.473735

1-sigma variation

Unit

MOID

Value

0.001110

1-sigma variation

Unit

Orbit Period

Value

529.2670

1-sigma variation

Unit

U parameter

Value

6.3

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	6.13086E-9	3.84615E-9	9.50608E-9	1.22656E-7	-2.37821E-7	-6.94064E-6
e	3.84615E-9	2.41286E-9	5.96337E-9	7.69434E-8	-1.49184E-7	-4.35416E-6
i	9.50608E-9	5.96337E-9	1.47921E-8	1.91091E-7	-3.69790E-7	-1.07616E-5
Ω	1.22656E-7	7.69434E-8	1.91091E-7	2.47003E-6	-4.77655E-6	-1.38855E-4
ω	-2.37821E-7	-1.49184E-7	-3.69790E-7	-4.77655E-6	9.25128E-6	2.69228E-4
M	-6.94064E-6	-4.35416E-6	-1.07616E-5	-1.38855E-4	2.69228E-4	7.85737E-3

Date of computation: 2025-09-10 00:30 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

Unit

Source

[-]

Quality

Value

Unit

Source

[-]

Amplitude

Value

Unit

mag

Source

[-]

Rotation Direction

Value

Unit

Source

[-]

Spinvector L

Value

Unit

Source

[-]

Spinvector B

Value

Unit

Source

[-]

Taxonomy
Taxonomy (all)

Taxonomy

Value

Unit

Source

Taxonomy

Value

Unit

Source

[-]

Taxonomy (all)

Value

Unit

Source

[-]

Absolute Magnitude (H)
Slope Parameter (G)

H / G

Value

Unit

Source

Absolute Magnitude (H)

Value

30.321

Unit

mag

Source

[1]

Slope Parameter (G)

Value

0.15**

Unit

mag

Source

[1]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.05 - 0.25

Unit

Source

[2]

Diameter

Value

2.3 - 5*

Unit

Source

[2]

Color Index Information

Color Index Information

Value

Unit

Source

Color Index Information

Value

Unit

mag

Source

[-]

Sightings

Sightings

Value

Unit

Source

Sightings

Value

Unit

Source

[-]

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Sources

No.	Name	Additional
[1]	ESA Aegis	ESA orbit determination and impact monitoring system
[2]	Estimation	Estimated from absolute magnitude

Observational Information

Arc Length
Unobserved
Normalized RMS of residuals

Arc Information

Value

Unit

Source

Arc Length

Value

Unit

Source

[1]

Unobserved

Value

1388

Unit

Source

[1]

Normalized RMS of residuals

Value

0.719646

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2021-11-29.174657

Unit

Source

[2]

Last Observation

Value

2021-12-02.149973

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

27 (0)

Unit

Source

[1]

Radar Summary

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

Radar

Value

Unit

Source

First Observation

Value

Unit

Source

[-]

Last Observation

Value

Unit

Source

[-]

Delay (Discarded)

Value

0 (0)

Unit

Source

[-]

Doppler (Discarded)

Value

0 (0)

Unit

Source

[-]

Total Radar Observations (Discarded)

Value

0 (0)

Unit

Source

[-]

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

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 2021WR4 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	1951-01-28 03:57	1185.0	0.0180261	0.0120500	0.0022012
EARTH	1954-01-22 13:26	121.7	0.0090307	0.0090099	0.0000079
EARTH	1957-02-07 19:32	129.7	0.0772561	0.0742233	0.0010112
EARTH	1960-02-18 09:30	101.1	0.1917059	0.1865852	0.0017069
MARS	2001-04-24 15:13	83.8	0.0247712	0.0118562	0.0046485
EARTH	2018-11-13 18:25	202.1	0.0953392	0.0906648	0.0015581
EARTH	2021-12-01 13:05	< 1 min	0.0028751	0.0028738	0.0000004
EARTH	2035-02-20 22:13	708.1	0.1294236	0.1070007	0.0074765
EARTH	2050-11-25 00:07	> 1 d	0.0270427	0.0048927	0.0074041
EARTH	2063-11-11 17:59	> 1 d	0.1463026	0.0000537	0.1171099
EARTH	2087-02-19 01:28	> 1 w	0.0930476	0.0069365	0.1532898
EARTH	2100-02-09 20:22	> 1 w	0.0263454	0.0066704	0.0736405
EARTH	2115-11-23 07:30	> 1 mo	0.0532441	0.0012998	1.0632278

Download as:

Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
336.16799950	328.52107910	0.00111837	MINIMUM
23.50486848	28.21265653	0.00657672	MINIMUM
0.13514583	358.74491138	0.02535140	SADDLE
179.94944136	178.49448480	0.58612771	SADDLE
359.89918344	178.44576593	1.97498072	SADDLE
179.93950806	358.48723095	2.58604367	MAXIMUM

Download:

MOID Plots

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

Level lines of the squared distance function

2021WR4

Date in UTC	MJD	σ	σ_imp	Distance ± Width in RE	Stretching in RE	IP	Impact energy	PS	TS
2098-02-09.972	87378.972	-2.907	0.000	0.52 ± 0.000	2.47E7	1.29E-9	5.00E-4	-11.87	0


Based on 27 optical observations (of which 0 are rejected as outliers) from 2021/11/29.175 to 2021/12/02.150.
Coordinates are given on the Target Plane.
Unit is one Earth radius, but impact cross section has radius between 2.77 and 2.77 Earth radii.
Coordinates for LOV = EQU scaled= 1 second= F.
AstOD software version= 4.0, Date of computation=20250805 130500.123 UTC.

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Download Impactor Table as: