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Asteroid Near-Earth

2021 RS

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(2021 RS)

Where is it now

Distance from Sun
1.057 AU
True anomaly
171.77°
Distance from Earth
0.951 AU
As of
20 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 RS — 1.057 AU from the Sun 2021 RS
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 2021 RS is 0.951 AU from Earth today (7.9 light-minutes).

In the sky

Right ascension
18h 17m 16s
Declination
-23° 57′ 39″
Constellation
Sagittarius
Distance from Earth
0.95 AU
Elongation from the Sun
65.69° — well clear of the Sun

Favours the southern hemisphere; low or below the horizon from far north.

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
0.904 AU
Eccentricity
0.1711
Inclination
2.16°
Orbital period
314.2 days
Perihelion
0.75 AU
Aphelion
1.059 AU
Longitude of ascending node
347.04°
Argument of periapsis
173.45°
Epoch · J2000
2461200.5
Orbit class · ATE
Aten
Earth MOID · 9.1 LD
0.0233 AU
Tisserand (Jupiter)
6.574

Orbit quality

Orbit poorly determined (uncertainty code 6).

Observations used
148
Data arc
43 days
First observed
4 September 2021
Last observed
17 October 2021
Residual RMS
0.48 ″
Solution · Otto Matic
26 October 2021

Physical properties

Rotation period
6.12 hours

Visual & observation

Absolute magnitude (H)
24.94

Discovery & classification

Aten Near-Earth Object

Close approaches 95 on record

Flyby geometry
Ecliptic flyby of 2021 RS at 2027-07-28 02:06 UTC Top-down view of the ecliptic, Earth at the centre, for the 2027-07-28 02:06 UTC close approach of 2021 RS. Catalogue miss distance 10.3 LD · 3.98 × 10⁶ km. The curve is the geocentric path from 2027-07-25 to 2027-07-31, 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 south of the ecliptic. The path is a geocentric ecliptic ephemeris from JPL Horizons. The inset is a heliocentric view and is approximate. Sun 26 Jul 30 Jul 10.3 LD · 3.98 × 10⁶ km 2027-07-28 02:06 UTC Earth Moon Heliocentric, approximate

Top-down view of the ecliptic, Earth at the centre, for the 2027-07-28 02:06 UTC close approach of 2021 RS. Catalogue miss distance 10.3 LD · 3.98 × 10⁶ km. The curve is the geocentric path from 2027-07-25 to 2027-07-31, 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 south 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
2027-07-28 02:06:00 Earth 0.0266 AU 10.3 LD 4.1 km/s
2028-01-03 18:03:00 Earth 0.1865 AU 72.6 LD 4.6 km/s
2033-07-25 03:03:00 Earth 0.1873 AU 72.9 LD 9.6 km/s
2034-02-12 09:41:00 Earth 0.2314 AU 90.1 LD 6.9 km/s
2034-10-10 02:59:00 Earth 0.4514 AU 175.7 LD 17.8 km/s
2039-08-01 06:30:00 Earth 0.3602 AU 140.2 LD 14.9 km/s
2040-03-15 19:25:00 Earth 0.2392 AU 93.1 LD 7.1 km/s
2040-10-16 13:12:00 Earth 0.2836 AU 110.4 LD 12.6 km/s
2046-10-21 23:51:00 Earth 0.1381 AU 53.8 LD 8.1 km/s
2052-05-08 17:07:00 Earth 0.1937 AU 75.4 LD 4.6 km/s

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

Sources