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Asteroid Near-Earth

2021 ER

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(2021 ER)

Where is it now

Distance from Sun
0.813 AU
True anomaly
68.22°
Distance from Earth
0.865 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 ER — 0.813 AU from the Sun 2021 ER
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 2021 ER is 0.865 AU from Earth today (7.2 light-minutes).

In the sky

Right ascension
10h 25m 53s
Declination
+04° 26′ 25″
Constellation
Sextans
Distance from Earth
0.87 AU
Elongation from the Sun
51.28° — near the Sun — look low at dusk or dawn

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
0.883 AU
Eccentricity
0.1572
Inclination
5.45°
Orbital period
302.8 days
Perihelion
0.744 AU
Aphelion
1.021 AU
Longitude of ascending node
161.64°
Argument of periapsis
213.31°
Epoch · J2000
2461200.5
Orbit class · ATE
Aten
Earth MOID · 0.0 LD
0 AU
Tisserand (Jupiter)
6.706

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
84
Data arc
5 years
First observed
5 March 2021
Last observed
7 March 2026
Residual RMS
0.77 ″
Solution · Otto Matic
9 March 2026

Visual & observation

Absolute magnitude (H)
27.01

Discovery & classification

Aten Near-Earth Object

Close approaches 46 on record

Flyby geometry
Ecliptic flyby of 2021 ER at 2030-12-20 06:02 UTC Top-down view of the ecliptic, Earth at the centre, for the 2030-12-20 06:02 UTC close approach of 2021 ER. Catalogue miss distance 76.1 LD · 2.92 × 10⁷ km. The curve is the geocentric path from 2030-12-17 to 2030-12-23, 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 76.1 LD · 2.92 × 10⁷ km 2030-12-20 06:02 UTC Earth Moon Heliocentric, approximate

Top-down view of the ecliptic, Earth at the centre, for the 2030-12-20 06:02 UTC close approach of 2021 ER. Catalogue miss distance 76.1 LD · 2.92 × 10⁷ km. The curve is the geocentric path from 2030-12-17 to 2030-12-23, 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
2030-12-20 06:02:00 Earth 0.1955 AU 76.1 LD 3.5 km/s
2031-04-29 05:12:00 Earth 0.1075 AU 41.8 LD 5.3 km/s
2036-08-10 20:18:00 Venus 0.0456 AU 17.8 LD 5.1 km/s
2039-02-12 19:31:00 Venus 0.0884 AU 34.4 LD 6.8 km/s
2050-03-02 02:12:00 Earth 0.0049 AU 1.9 LD 4.4 km/s
2050-03-02 11:12:00 Moon 0.0038 AU 1.5 LD 4.2 km/s
2050-07-06 08:03:00 Earth 0.161 AU 62.6 LD 3.4 km/s
2053-03-27 07:32:00 Venus 0.0566 AU 22.0 LD 4.7 km/s
2060-12-26 20:00:00 Earth 0.1811 AU 70.5 LD 3.1 km/s
2061-05-03 06:09:00 Earth 0.101 AU 39.3 LD 4.6 km/s

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

Sources