Asteroids

2021ER help

Last update: 2025-11-24 16:53 UTC

Orbital Properties

Epoch

61000.0

MJD

Orbit type

Aten

Perihelion (q)

0.748

Aphelion (Q)

1.022

Eccentricity (e)

0.155

Inclination (i)

5.5

deg

Orbit period (P)

304.2

Earth MOID

0.00096

U parameter

5.7

Next Earth close approach

Date

2026-03-07

Nominal distance (from Earth center)

0.0174

2602263

Maximum Brightness

20.4

mag

Risk

Object is in risk list

Physical Properties

Absolute Magnitude (H)

26.9

mag

Diameter

11 - 25*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-03-05

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

0.885293

1-sigma variation

0.000012

Unit

Eccentricity (e)

Value

0.154573

1-sigma variation

0.000020

Unit

Inclination (i)

Value

5.5214

1-sigma variation

0.0008

Unit

Long. of Ascending Node (Ω)

Value

162.0181

1-sigma variation

0.0001

Unit

Arg. of Perihelion (ω)

Value

214.1518

1-sigma variation

0.0008

Unit

Mean Anomaly (M)

Value

15.67898

1-sigma variation

0.04104

Unit

Perihelion distance

Value

0.748450

1-sigma variation

Unit

Aphelion distance

Value

1.022135

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

-0.001273

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.242950

1-sigma variation

Unit

MOID

Value

0.000961

1-sigma variation

Unit

Orbit Period

Value

304.2487

1-sigma variation

Unit

U parameter

Value

5.7

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	1.41802E-10	-2.34735E-10	-9.80167E-9	-1.57913E-9	8.96863E-9	-4.88651E-7
e	-2.34735E-10	3.88582E-10	1.62262E-8	2.61457E-9	-1.48436E-8	8.08895E-7
i	-9.80167E-9	1.62262E-8	6.77645E-7	1.09250E-7	-6.19687E-7	3.37762E-5
Ω	-1.57913E-9	2.61457E-9	1.09250E-7	1.77185E-8	-9.97304E-8	5.44130E-6
ω	8.96863E-9	-1.48436E-8	-6.19687E-7	-9.97304E-8	5.68301E-7	-3.09078E-5
M	-4.88651E-7	8.08895E-7	3.37762E-5	5.44130E-6	-3.09078E-5	1.68390E-3

Date of computation: 2025-11-24 16:53 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

26.909

Unit

mag

Source

[1]

Slope Parameter (G)

Value

0.15**

Unit

Source

[1]

Albedo
Diameter

Size and albedo

Value

Unit

Source

Albedo

Value

0.05 - 0.25

Unit

Source

[2]

Diameter

Value

11 - 25*

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

1783

Unit

Source

[1]

Normalized RMS of residuals

Value

0.743162

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2021-03-05.386516

Unit

Source

[2]

Last Observation

Value

2021-04-08.271637

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

94 (5)

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 2021ER from 1950 to 2126

Body	Date in UTC	Time uncert. in min	Nominal distance in au	Min. possible distance in au	Distance uncert. in au
EARTH	1965-04-10 20:16	842.3	0.0782168	0.0758053	0.0008255
EARTH	1976-02-27 05:45	201.3	0.0743527	0.0536634	0.0069037
EARTH	1976-07-30 05:32	> 1 d	0.1847581	0.1788287	0.0021374
EARTH	1982-05-10 17:58	62.8	0.1763773	0.1705011	0.0019709
EARTH	1993-03-15 14:34	> 1 d	0.0416710	0.0258676	0.0053981
EARTH	2004-02-28 13:44	126.9	0.0386546	0.0335424	0.0017043
EARTH	2004-07-19 14:42	> 1 d	0.1720279	0.1701981	0.0006239
EARTH	2010-05-11 16:30	7.9	0.1919814	0.1878043	0.0013975
EARTH	2021-03-03 23:06	< 1 min	0.0045788	0.0045768	0.0000007
EARTH	2026-03-07 02:10	218.7	0.0173951	0.0158530	0.0005142
EARTH	2030-12-22 23:13	> 1 d	0.1920488	0.1866593	0.0017967
EARTH	2031-04-28 09:34	428.9	0.1033725	0.0975414	0.0020281
VENUS	2036-08-13 05:20	> 1 d	0.0314444	0.0148972	0.0067573
EARTH	2045-02-27 01:26	8.1	0.1966776	0.1741749	0.0075012
EARTH	2050-03-08 13:56	> 1 d	0.0214283	0.0009595	0.0123142
EARTH	2064-02-27 21:20	> 1 w	0.0284875	0.0009379	0.1374090
EARTH	2064-06-28 15:05	> 1 mo	0.1727398	0.1308990	0.0683291
EARTH	2069-04-30 14:38	> 1 d	0.1401749	0.0815585	0.2489255
EARTH	2083-02-25 13:54	> 1 d	0.0933815	0.0016157	0.1395178
EARTH	2083-07-21 05:20	> 1 mo	0.1989023	0.1680718	0.0748199
EARTH	2088-04-09 08:45	> 1 mo	0.0727370	0.0576948	0.1626599
VENUS	2094-06-08 20:43	> 1 mo	0.0464785	0.0059470	0.5307443
EARTH	2102-02-27 03:32	> 1 d	0.1435304	0.0040523	0.6021361
EARTH	2107-04-01 10:00	> 1 mo	0.0628057	0.0390782	0.6532966
EARTH	2121-02-27 00:40	> 1 w	0.1474230	0.0044782	2.1637938
VENUS	2125-11-03 10:15	> 1 mo	0.0262859	0.0135237	1.2075374

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
140.92913579	60.21967908	0.00096118	MINIMUM
357.50599354	273.15626939	0.25505280	SADDLE
352.30604157	87.09689230	1.74895464	SADDLE
173.09022229	267.86637337	2.02182142	MAXIMUM

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MOID Plots

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

Level lines of the squared distance function

2021ER

Date in UTC	MJD	σ	Distance ± Width in RE	Stretching in RE	IP	Impact energy	PS
2076-02-29.432	79362.432	1.556	2.54 ± 0.000	5.10E5	5.32E-7	5.53E-2	-7.47
2084-02-28.468	82283.468	1.386	2.36 ± 0.003	5.38E4	1.18E-5	5.50E-2	-6.19
2110-03-01.669	91780.669	3.177	1.30 ± 0.005	4.36E4	2.90E-7	5.52E-2	-7.95
2110-03-01.687	91780.687	3.177	2.19 ± 0.001	1.09E5	8.95E-8	5.52E-2	-8.46


Based on 94 optical observations (of which 5 are rejected as outliers) from 2021/03/05.387 to 2021/04/08.272.
Coordinates are given on the Target Plane.
Unit is one Earth radius, but impact cross section has radius between 2.79 and 2.79 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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