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Asteroid

Amalthea

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113 Amalthea (A871 EA)

Where is it now

Distance from Sun
2.558 AU
True anomaly
154.57°
Distance from Earth
1.775 AU
As of
21 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.

Orbit of Mercury Orbit of Venus Orbit of Mars Sun Earth — 0.995 AU from the Sun Earth Amalthea — 2.558 AU from the Sun Amalthea
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Amalthea is 1.775 AU from Earth today (14.8 light-minutes).

In the sky

Right ascension
23h 00m 56s
Declination
-12° 44′ 34″
Constellation
Aquarius
Distance from Earth
1.78 AU
Elongation from the Sun
132.65° — 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
2.376 AU
Eccentricity
0.0863
Inclination
5.04°
Orbital period
3.66 years
Perihelion
2.171 AU
Aphelion
2.581 AU
Longitude of ascending node
123.32°
Argument of periapsis
80.25°
Epoch · J2000
2461200.5
Orbit class · MBA
Main-belt asteroid
Earth MOID · 457.4 LD
1.1752 AU
Tisserand (Jupiter)
3.531

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
5,423
Data arc
154.5 years
First observed
12 March 1871
Last observed
22 September 2025
Residual RMS
0.43 ″
Solution · Otto Matic
11 March 2026

Physical properties

Mean radius
25 km
Rotation period
9.95 hours

Visual & observation

Geometric albedo
0.224
Absolute magnitude (H)
8.53
Colour index (B–V)
0.93
Spectral type (SMASS)
S
Spectral type (Tholen)
S
Colour index (U–B)
0.52

Discovery & classification

Discovered by
Luther, R.
Discovery date
12 March 1871
Discovery site
Dusseldorf

Also known as 113 · A871 EA · 1931 TN3 · 1951 CY

Main-Belt Asteroid Named

Sources