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Asteroid Near-Earth

2021 SO

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(2021 SO)

Where is it now

Distance from Sun
0.926 AU
True anomaly
222.67°
Distance from Earth
0.301 AU
As of
16 October 2026

Two-body Kepler propagation — accurate to ~0.1% for major planets over decades, less so for highly-perturbed bodies. Use JPL Horizons for high precision.

Sun Earth — 0.997 AU from the Sun Earth 2021 SO — 0.926 AU from the Sun 2021 SO
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 2021 SO is 0.301 AU from Earth today (2.5 light-minutes).

In the sky

Right ascension
09h 08m 43s
Declination
+10° 27′ 33″
Constellation
Cancer
Distance from Earth
0.3 AU
Elongation from the Sun
67.53° — well clear of the Sun

Visible from both hemispheres.

From your location

See how high it is right now, whether it is up after civil twilight, and when it rises and sets where you are.

How do I find my coordinates?

Google Maps on a computer

  1. Right-click the spot where you'll be observing.
  2. The first line of the menu is the coordinates, e.g. 51.50722, -0.12758 — click it and they're copied.
  3. Paste them above.

Google Maps on a phone

  1. Press and hold the spot to drop a pin.
  2. The coordinates appear in the search bar (or on the pin's card) — tap to copy, then paste above.

A full Google Maps link works too, but the short maps.app.goo.gl share links don't carry coordinates — copy the numbers instead. We round to about a kilometre; that's all the sky calculation needs.

Know your what3words address? Paste it, e.g. ///filled.count.soap. This is optional — the three words are sent to what3words to convert them, and we don't store the address or the result.

Your location stays in your browser and is sent only for this calculation. Using a what3words address is optional; if you do, the three words go to what3words to be converted and we don't record them. Set a location first, then you can save an email alert for this object. See our privacy policy.

Two-body approximation, good to about a degree for the planets — enough to find the constellation and know whether it is up.

Orbital elements

Semi-major axis
0.791 AU
Eccentricity
0.3103
Inclination
4.13°
Orbital period
257.1 days
Perihelion
0.546 AU
Aphelion
1.037 AU
Longitude of ascending node
194.65°
Argument of periapsis
343.57°
Epoch · J2000
2461200.5
Orbit class · ATE
Aten
Earth MOID · 3.4 LD
0.0087 AU
Tisserand (Jupiter)
7.315

Orbit quality

Orbit poorly determined (uncertainty code 7).

Observations used
50
Data arc
22 days
First observed
18 September 2021
Last observed
10 October 2021
Residual RMS
0.44 ″
Solution · Otto Matic
10 October 2021

Visual & observation

Absolute magnitude (H)
25.35

Discovery & classification

Aten Near-Earth Object

Close approaches 117 on record

Flyby geometry
Ecliptic flyby of 2021 SO at 2026-10-16 14:25 UTC Top-down view of the ecliptic, Earth at the centre, for the 2026-10-16 14:25 UTC close approach of 2021 SO. Catalogue miss distance 124.2 LD · 4.77 × 10⁷ km. The curve is the geocentric path from 2026-10-13 to 2026-10-19, with a mark at UTC midnights and an arrow for the direction of motion. The circle is the Moon’s mean orbit; the Moon is plotted at closest approach. A ray shows the Sun’s direction. The labelled distance is the full separation. The drawn radius is the part that lies in the ecliptic plane. The path is a geocentric ecliptic ephemeris from JPL Horizons. The inset is a heliocentric view and is approximate. Sun 124.2 LD · 4.77 × 10⁷ km 2026-10-16 14:25 UTC Earth Moon Heliocentric, approximate

Top-down view of the ecliptic, Earth at the centre, for the 2026-10-16 14:25 UTC close approach of 2021 SO. Catalogue miss distance 124.2 LD · 4.77 × 10⁷ km. The curve is the geocentric path from 2026-10-13 to 2026-10-19, with a mark at UTC midnights and an arrow for the direction of motion. The circle is the Moon’s mean orbit; the Moon is plotted at closest approach. A ray shows the Sun’s direction. The labelled distance is the full separation. The drawn radius is the part that lies in the ecliptic plane. The path is a geocentric ecliptic ephemeris from JPL Horizons. The inset is a heliocentric view and is approximate.

JPL Horizons

When (UTC) Body Distance Lunar distances Relative speed
2026-10-16 14:25:00 Earth 0.3191 AU 124.2 LD 16.7 km/s
2026-11-22 08:11:00 Venus 0.1292 AU 50.3 LD 16.7 km/s
2027-10-09 19:55:00 Venus 0.1266 AU 49.3 LD 9 km/s
2028-08-26 01:23:00 Earth 0.1399 AU 54.5 LD 10.5 km/s
2029-01-05 05:32:00 Earth 0.3371 AU 131.2 LD 8.1 km/s
2031-03-26 16:20:00 Earth 0.4506 AU 175.4 LD 16.4 km/s
2031-10-26 04:01:00 Venus 0.0996 AU 38.8 LD 15.1 km/s
2033-10-21 16:35:00 Earth 0.1054 AU 41.0 LD 9.7 km/s
2035-08-31 22:57:00 Earth 0.3377 AU 131.4 LD 17.2 km/s
2036-02-04 17:49:00 Earth 0.4048 AU 157.6 LD 13 km/s

Next ten from today. 1 lunar distance = 384,400 km. Source: JPL close-approach data.

Sources