Asteroids

2021HU help

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

Orbital Properties

Epoch

61200.0

MJD

Orbit type

Apollo

Perihelion (q)

0.876

Aphelion (Q)

2.284

Eccentricity (e)

0.446

Inclination (i)

6.9

deg

Orbit period (P)

725.4

Earth MOID

0.01806

U parameter

0.0

Next Earth close approach

Date

Nominal distance (from Earth center)

Maximum Brightness

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

25.1

mag

Diameter

25 - 60*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-04-17

Observatory

University of Arizona 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

61200.0000

1-sigma variation

Unit

MJD

Semimajor Axis

Value

1.579999

1-sigma variation

3.348E-9

Unit

Eccentricity (e)

Value

0.445665

1-sigma variation

1.372E-7

Unit

Inclination (i)

Value

6.9420

1-sigma variation

8.969E-6

Unit

Long. of Ascending Node (Ω)

Value

44.8140

1-sigma variation

3.241E-5

Unit

Arg. of Perihelion (ω)

Value

225.2660

1-sigma variation

3.772E-5

Unit

Mean Anomaly (M)

Value

185.95696

1-sigma variation

0.00001

Unit

Perihelion distance

Value

0.875849

1-sigma variation

Unit

Aphelion distance

Value

2.284148

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.852866

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.044421

1-sigma variation

Unit

MOID

Value

0.018057

1-sigma variation

Unit

Orbit Period

Value

725.4099

1-sigma variation

Unit

U parameter

Value

0.0

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	1.12106E-17	-1.10721E-16	4.96026E-15	-4.30835E-14	8.14063E-15	-2.00459E-15
e	-1.10721E-16	1.88314E-14	-2.09135E-16	2.07657E-12	3.40407E-12	-1.21549E-12
i	4.96026E-15	-2.09135E-16	8.04386E-11	-2.21033E-10	2.22197E-10	-3.74165E-12
Ω	-4.30835E-14	2.07657E-12	-2.21033E-10	1.05032E-9	-4.31640E-10	-1.19670E-10
ω	8.14063E-15	3.40407E-12	2.22197E-10	-4.31640E-10	1.42302E-9	-2.38394E-10
M	-2.00459E-15	-1.21549E-12	-3.74165E-12	-1.19670E-10	-2.38394E-10	9.08880E-11

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

25.139

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

25 - 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

[-]

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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

1469

Unit

Source

[1]

Unobserved

Value

1280

Unit

Source

[1]

Normalized RMS of residuals

Value

0.529934

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2019-04-07.308065

Unit

Source

[2]

Last Observation

Value

2023-04-15.475854

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

67 (1)

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 2021HU 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	2007-08-29 06:14	< 1 min	0.1562899	0.1562880	0.0000006
EARTH	2009-08-20 22:35	< 1 min	0.1206933	0.1206928	0.0000002
EARTH	2011-08-07 03:29	< 1 min	0.1364363	0.1364354	0.0000003
EARTH	2013-07-14 09:53	< 1 min	0.1621729	0.1621721	0.0000003
EARTH	2015-06-23 02:39	< 1 min	0.1631000	0.1630994	0.0000002
EARTH	2017-05-31 21:17	< 1 min	0.1380413	0.1380409	0.0000001
EARTH	2019-05-12 15:37	< 1 min	0.0872674	0.0872671	0.0000001
EARTH	2021-04-29 10:51	< 1 s	0.0249484	0.0249482	0.0000001
EARTH	2023-04-23 10:16	< 1 s	0.0465213	0.0465211	0.0000001
EARTH	2025-04-16 16:50	< 1 s	0.1213542	0.1213539	0.0000001

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Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
325.53497410	111.62874755	0.01805661	MINIMUM
36.68939460	222.74195889	0.12028279	MINIMUM
6.29472513	175.54161090	0.16606630	SADDLE
180.83366559	346.08208648	1.30657062	SADDLE
0.94122545	346.73962943	1.85807648	SADDLE
179.95266241	165.54367989	3.29785527	MAXIMUM

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MOID Plots

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