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Asteroid

Mnemosyne

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57 Mnemosyne (A859 SA)

Where is it now

Distance from Sun
3.228 AU
True anomaly
251.85°
Distance from Earth
3.316 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 Mnemosyne — 3.228 AU from the Sun Mnemosyne
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Mnemosyne is 3.316 AU from Earth today (27.6 light-minutes).

In the sky

Right ascension
18h 55m 35s
Declination
-08° 19′ 50″
Constellation
Scutum
Distance from Earth
3.32 AU
Elongation from the Sun
76.15° — 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
3.156 AU
Eccentricity
0.1079
Inclination
15.23°
Orbital period
5.61 years
Perihelion
2.816 AU
Aphelion
3.497 AU
Longitude of ascending node
198.88°
Argument of periapsis
210.99°
Epoch · J2000
2461200.5
Orbit class · MBA
Main-belt asteroid
Earth MOID · 713.6 LD
1.8337 AU
Tisserand (Jupiter)
3.143

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
5,110
Data arc
166.3 years
First observed
22 December 1859
Last observed
14 April 2026
Residual RMS
0.4 ″
Solution · Otto Matic
5 June 2026

Physical properties

Mean radius
56 km
Rotation period
25.32 hours

Visual & observation

Geometric albedo
0.215
Absolute magnitude (H)
6.93
Colour index (B–V)
0.82
Spectral type (SMASS)
S
Spectral type (Tholen)
S
Colour index (U–B)
0.41

Discovery & classification

Discovered by
Luther, R.
Discovery date
22 September 1859
Discovery site
Dusseldorf

Also known as 57 · A859 SA · 1959 NT

Main-Belt Asteroid Named

Close approaches 2 on record

When (UTC) Body Distance Lunar distances Relative speed
2148-08-30 02:55:00 Juptr 1.9969 AU 777.2 LD 4.4 km/s

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

Sources