Asteroids

2021HC3 help

Last update: 2026-03-17 23:26 UTC

Orbital Properties

Epoch

61200.0

MJD

Orbit type

Apollo

Perihelion (q)

0.364

Aphelion (Q)

1.879

Eccentricity (e)

0.675

Inclination (i)

28.4

deg

Orbit period (P)

433.9

Earth MOID

0.04744

U parameter

2.2

Next Earth close approach

Date

2040-05-05

Nominal distance (from Earth center)

0.05962

8919298

Maximum Brightness

17.4

mag

Risk

Object is not in risk list

Physical Properties

Absolute Magnitude (H)

21.5

mag

Diameter

130 - 300*

Taxonomic type

Rotation period (T)

Discovery Information

Discovery Date

2021-04-30

Observatory

ATLAS-HKO, 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

1.121578

1-sigma variation

1.014E-7

Unit

Eccentricity (e)

Value

0.675498

1-sigma variation

4.381E-7

Unit

Inclination (i)

Value

28.3972

1-sigma variation

0.0001

Unit

Long. of Ascending Node (Ω)

Value

219.5336

1-sigma variation

7.172E-6

Unit

Arg. of Perihelion (ω)

Value

132.1473

1-sigma variation

4.861E-5

Unit

Mean Anomaly (M)

Value

59.62910

1-sigma variation

0.00022

Unit

Perihelion distance

Value

0.363954

1-sigma variation

Unit

Aphelion distance

Value

1.879203

1-sigma variation

Unit

Asc. Node-Earth Sep.

Value

0.108236

1-sigma variation

Unit

Desc. Node-Earth Sep.

Value

-0.573242

1-sigma variation

Unit

MOID

Value

0.047442

1-sigma variation

Unit

Orbit Period

Value

433.8533

1-sigma variation

Unit

U parameter

Value

2.2

1-sigma variation

Unit

Covariance Matrix

	a	e	i	Ω	ω	M
a	1.02763E-14	-3.78480E-14	1.77966E-12	2.91314E-13	-4.32418E-12	-2.23759E-11
e	-3.78480E-14	1.91920E-13	-8.26132E-12	-1.39906E-12	2.10800E-11	8.48484E-11
i	1.77966E-12	-8.26132E-12	2.90893E-9	3.41040E-10	-1.10803E-9	-4.00070E-9
Ω	2.91314E-13	-1.39906E-12	3.41040E-10	5.14340E-11	-1.89984E-10	-6.50305E-10
ω	-4.32418E-12	2.10800E-11	-1.10803E-9	-1.89984E-10	2.36337E-9	9.64947E-9
M	-2.23759E-11	8.48484E-11	-4.00070E-9	-6.50305E-10	9.64947E-9	4.88404E-8

Date of computation: 2026-03-17 23:26 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

21.489

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

130 - 300*

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

1556

Unit

Source

[1]

Unobserved

Value

1408

Unit

Source

[1]

Normalized RMS of residuals

Value

0.59148

Unit

Source

[1]

Astrometry Summary

First Observation
Last Observation
Total Optical Observations (Discarded)

Optical

Value

Unit

Source

First Observation

Value

2018-02-18.143168

Unit

Source

[2]

Last Observation

Value

2022-05-24.259195

Unit

Source

[2]

Total Optical Observations (Discarded)

Value

146 (3)

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

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 2021HC3 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	1964-04-29 12:36	2.8	0.1318566	0.1317121	0.0000482
EARTH	1983-05-02 17:45	2.0	0.0762577	0.0761659	0.0000306
EARTH	2002-05-04 02:19	< 1 min	0.0496558	0.0496396	0.0000054
EARTH	2021-05-04 18:04	< 1 s	0.0475922	0.0475921	0.0000000
EARTH	2040-05-05 11:51	< 1 min	0.0596218	0.0595959	0.0000086
EARTH	2059-05-07 16:44	1.2	0.0953646	0.0952825	0.0000274
EARTH	2078-05-09 00:32	1.3	0.1518296	0.1517055	0.0000414
EARTH	2084-04-27 11:14	2.6	0.1982500	0.1981169	0.0000443
EARTH	2103-05-01 23:42	2.6	0.1341500	0.1340176	0.0000441
EARTH	2122-05-04 03:13	2.2	0.0810962	0.0809989	0.0000324

Download as:

Stationary Points

Ecc. an. ast.	Ecc. an. Earth	Distance in au	Classification
276.90234177	121.77535015	0.04668407	MINIMUM
62.03756250	354.81073393	0.42459395	MINIMUM
348.47300959	228.86602832	0.69683756	SADDLE
171.74715789	69.82451792	1.01763779	SADDLE
352.45659474	58.78439501	1.33540362	SADDLE
182.13432066	254.43843269	2.84280891	MAXIMUM

Download:

MOID Plots

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