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Asteroid Near-Earth

2021 OS

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(2021 OS)

Where is it now

Distance from Sun
1.161 AU
True anomaly
177.9°
Distance from Earth
1 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 OS — 1.161 AU from the Sun 2021 OS
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 2021 OS is 1 AU from Earth today (8.3 light-minutes).

In the sky

Right ascension
18h 18m 48s
Declination
-12° 49′ 48″
Constellation
Serpens
Distance from Earth
1 AU
Elongation from the Sun
70.92° — 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
0.811 AU
Eccentricity
0.4326
Inclination
15.45°
Orbital period
266.6 days
Perihelion
0.46 AU
Aphelion
1.161 AU
Longitude of ascending node
294.31°
Argument of periapsis
218.1°
Epoch · J2000
2461200.5
Orbit class · ATE
Aten
Earth MOID · 3.8 LD
0.0097 AU
Tisserand (Jupiter)
7.105

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
197
Data arc
11.21 years
First observed
9 August 2013
Last observed
23 October 2024
Residual RMS
0.36 ″
Solution · Otto Matic
23 October 2024

Visual & observation

Absolute magnitude (H)
22.04

Discovery & classification

Aten Near-Earth Object

Close approaches 180 on record

Flyby geometry
Ecliptic flyby of 2021 OS at 2027-09-23 10:17 UTC Top-down view of the ecliptic, Earth at the centre, for the 2027-09-23 10:17 UTC close approach of 2021 OS. Catalogue miss distance 181.2 LD · 6.97 × 10⁷ km. The curve is the geocentric path from 2027-09-20 to 2027-09-26, 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. At closest approach the object is north of the ecliptic. The path is a geocentric ecliptic ephemeris from JPL Horizons. The inset is a heliocentric view and is approximate. Sun 181.2 LD · 6.97 × 10⁷ km 2027-09-23 10:17 UTC Earth Moon Heliocentric, approximate

Top-down view of the ecliptic, Earth at the centre, for the 2027-09-23 10:17 UTC close approach of 2021 OS. Catalogue miss distance 181.2 LD · 6.97 × 10⁷ km. The curve is the geocentric path from 2027-09-20 to 2027-09-26, 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. At closest approach the object is north of the ecliptic. 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
2027-09-23 10:17:00 Earth 0.4656 AU 181.2 LD 23.3 km/s
2029-07-20 02:03:00 Earth 0.1105 AU 43.0 LD 16 km/s
2030-01-19 04:08:00 Earth 0.496 AU 193.0 LD 22 km/s
2032-08-19 08:54:00 Earth 0.2389 AU 93.0 LD 10.3 km/s
2032-11-23 18:40:00 Earth 0.3699 AU 144.0 LD 11.2 km/s
2034-08-04 16:08:00 Venus 0.1185 AU 46.1 LD 16.4 km/s
2035-09-30 16:54:00 Earth 0.3369 AU 131.1 LD 17.7 km/s
2037-07-25 15:21:00 Earth 0.2833 AU 110.2 LD 21.1 km/s
2040-07-26 19:38:00 Earth 0.1467 AU 57.1 LD 10.5 km/s
2040-12-19 05:46:00 Earth 0.4302 AU 167.4 LD 16.6 km/s

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

Sources