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Asteroid

Io

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85 Io (A865 SA)

Where is it now

Distance from Sun
3 AU
True anomaly
140.24°
Distance from Earth
2.958 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 Io — 3 AU from the Sun Io
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Io is 2.958 AU from Earth today (24.6 light-minutes).

In the sky

Right ascension
08h 20m 39s
Declination
+07° 07′ 54″
Constellation
Cancer
Distance from Earth
2.96 AU
Elongation from the Sun
82.83° — 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
2.654 AU
Eccentricity
0.193
Inclination
11.96°
Orbital period
4.32 years
Perihelion
2.141 AU
Aphelion
3.166 AU
Longitude of ascending node
203.04°
Argument of periapsis
122.96°
Epoch · J2000
2461200.5
Orbit class · MBA
Main-belt asteroid
Earth MOID · 450.2 LD
1.1568 AU
Tisserand (Jupiter)
3.332

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
8,726
Data arc
160.5 years
First observed
21 September 1865
Last observed
26 March 2026
Residual RMS
0.31 ″
Solution · Otto Matic
5 June 2026

Physical properties

Mean radius
77 km
Rotation period
6.88 hours

Visual & observation

Geometric albedo
0.067
Absolute magnitude (H)
7.93
Colour index (B–V)
0.67
Spectral type (SMASS)
B
Spectral type (Tholen)
FC
Colour index (U–B)
0.29

Discovery & classification

Discovered by
Peters, C. H. F.
Discovery date
19 September 1865
Discovery site
Clinton

Also known as 85 · A865 SA · A899 LA · A899 UA

Main-Belt Asteroid Named

Sources