Asteroids

2021HH help

Last update: 2026-07-30 14:25 UTC

Orbital Properties

Epoch

61200.0

MJD

Orbit type

Apollo

Perihelion (q)

0.670

Aphelion (Q)

2.217

Eccentricity (e)

0.536

Inclination (i)

9.1

deg

Orbit period (P)

633.4

Earth MOID

0.01844

U parameter

8.4

Next Earth close approach

Date

2026-10-25

Nominal distance (from Earth center)

0.01837

2748353

Maximum Brightness

19.2

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

mag

Diameter

27 - 60*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-04-16

Observatory

Pan-STARRS 1, Haleakala

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

61200.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

1.443324

1-sigma variation

0.002222

Unit

Eccentricity (e)

Value

0.535903

1-sigma variation

0.000971

Unit

Inclination (i)

Value

9.1246

1-sigma variation

0.0176

Unit

Long. of Ascending Node (Ω)

Value

206.0001

1-sigma variation

0.0007

Unit

Arg. of Perihelion (ω)

Value

100.7200

1-sigma variation

0.0054

Unit

Mean Anomaly (M)

Value

310.15586

1-sigma variation

2.36237

Unit

Perihelion distance

Value

0.669843

1-sigma variation

Unit

Aphelion distance

Value

2.216805

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.139217

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.060834

1-sigma variation

Unit

MOID

Value

0.018437

1-sigma variation

Unit

Orbit Period

Value

633.3506

1-sigma variation

Unit

U parameter

Value

8.4

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	4.93754E-6	2.15667E-6	3.91667E-5	1.51997E-6	-1.20109E-5	-5.24932E-3
e	2.15667E-6	9.42012E-7	1.71076E-5	6.63909E-7	-5.24624E-6	-2.29285E-3
i	3.91667E-5	1.71076E-5	3.10689E-4	1.20576E-5	-9.52756E-5	-4.16399E-2
Ω	1.51997E-6	6.63909E-7	1.20576E-5	4.68266E-7	-3.69763E-6	-1.61595E-3
ω	-1.20109E-5	-5.24624E-6	-9.52756E-5	-3.69763E-6	2.92211E-5	1.27694E-2
M	-5.24932E-3	-2.29285E-3	-4.16399E-2	-1.61595E-3	1.27694E-2	5.58078E0

Date of computation: 2026-07-30 14:25 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

24.982

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

27 - 60*

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

[-]

Download this part as:

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

1954

Unit

Source

[1]

Normalized RMS of residuals

Value

0.413842

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2021-04-16.486916

Unit

Source

[2]

Last Observation

Value

2021-04-29.85482

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

52 (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

Filters

Initial Date: *

Final Date: *

Normalised Only accepted

Max residual (arcsec):

* - these fields are required

Plot

Computation parameters

As seen from:

Initial Date: *

Final Date: *

Output option:

One line per time step

Time step:*

* - these fields are required

Note: Ephemerides requests are limited to a maximum of 1000 points and a final date not exceeding 2040/12/31 00:00.

Close Approaches for 2021HH 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	1962-05-02 01:36	> 1 w	0.0744909	0.0318606	0.2816365
EARTH	1967-10-30 02:39	> 1 w	0.0777939	0.0164829	0.3054562
EARTH	1995-04-25 17:24	> 1 w	0.0667078	0.0337561	0.2011429
EARTH	2000-10-22 02:16	> 1 w	0.0551135	0.0174570	0.2740278
EARTH	2021-04-29 00:14	< 1 s	0.0367108	0.0365194	0.0000638
EARTH	2026-10-25 23:59	> 1 d	0.0183716	0.0182999	0.0065539
EARTH	2047-05-03 17:01	> 1 mo	0.0879405	0.0344290	1.4403026
EARTH	2052-10-30 00:45	> 1 mo	0.0807608	0.0197795	1.7848303
EARTH	2080-04-23 00:18	> 1 d	0.1135330	0.0358572	0.1067493
EARTH	2085-10-18 21:38	> 1 w	0.1090594	0.0221713	0.2104971
EARTH	2106-04-30 23:52	> 1 mo	0.0405966	0.0378872	0.4589412
EARTH	2111-10-28 23:11	> 1 mo	0.0286376	0.0216059	1.6142492

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
54.06347084	288.87985925	0.01843711	MINIMUM
303.57081668	112.68515481	0.03476624	MINIMUM
358.25983748	199.73780152	0.36934935	SADDLE
179.43244411	21.96969375	1.25355070	SADDLE
358.98338103	21.08586895	1.64961362	SADDLE
179.86889790	202.20572839	3.22386451	MAXIMUM

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MOID Plots

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