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Asteroid Near-Earth

2021 SY3

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(2021 SY3)

Where is it now

Distance from Sun
1.005 AU
True anomaly
218.93°
Distance from Earth
0.942 AU
As of
19 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 — 0.996 AU from the Sun Earth 2021 SY3 — 1.005 AU from the Sun 2021 SY3
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 2021 SY3 is 0.942 AU from Earth today (7.8 light-minutes).

In the sky

Right ascension
09h 56m 21s
Declination
+18° 07′ 54″
Constellation
Leo
Distance from Earth
0.94 AU
Elongation from the Sun
62.3° — well clear of the Sun

Favours the northern hemisphere; low or below the horizon from far south.

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
0.86 AU
Eccentricity
0.2585
Inclination
5°
Orbital period
291.5 days
Perihelion
0.638 AU
Aphelion
1.083 AU
Longitude of ascending node
3.92°
Argument of periapsis
219.61°
Epoch · J2000
2461200.5
Orbit class · ATE
Aten
Earth MOID · 0.1 LD
0.0002 AU
Tisserand (Jupiter)
6.831

Orbit quality

Orbit poorly determined (uncertainty code 7).

Observations used
25
Data arc
11 days
First observed
30 September 2021
Last observed
11 October 2021
Residual RMS
0.63 ″
Solution · Otto Matic
19 October 2021

Visual & observation

Absolute magnitude (H)
27

Discovery & classification

Aten Near-Earth Object

Close approaches 105 on record

Flyby geometry
Ecliptic flyby of 2021 SY3 at 2029-10-19 03:41 UTC Top-down view of the ecliptic, Earth at the centre, for the 2029-10-19 03:41 UTC close approach of 2021 SY3. Catalogue miss distance 35.4 LD · 1.36 × 10⁷ km. The curve is the geocentric path from 2029-10-16 to 2029-10-22, 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 35.4 LD · 1.36 × 10⁷ km 2029-10-19 03:41 UTC Earth Moon Heliocentric, approximate

Top-down view of the ecliptic, Earth at the centre, for the 2029-10-19 03:41 UTC close approach of 2021 SY3. Catalogue miss distance 35.4 LD · 1.36 × 10⁷ km. The curve is the geocentric path from 2029-10-16 to 2029-10-22, 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
2029-10-19 03:41:00 Earth 0.0909 AU 35.4 LD 5.6 km/s
2030-02-16 17:04:00 Earth 0.2523 AU 98.2 LD 6.3 km/s
2030-05-09 09:59:00 Venus 0.1179 AU 45.9 LD 13.8 km/s
2032-07-22 02:14:00 Venus 0.0586 AU 22.8 LD 11.3 km/s
2033-11-07 03:03:00 Earth 0.1096 AU 42.6 LD 5.7 km/s
2037-07-25 10:47:00 Earth 0.2766 AU 107.7 LD 5.9 km/s
2037-12-01 15:53:00 Earth 0.1041 AU 40.5 LD 5.5 km/s
2038-04-27 06:05:00 Venus 0.0619 AU 24.1 LD 6.3 km/s
2041-07-07 16:08:00 Earth 0.3143 AU 122.3 LD 8.1 km/s
2041-12-20 07:00:00 Earth 0.0854 AU 33.2 LD 6.9 km/s

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

Sources