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Trans-Neptunian object

2015 SP21

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(2015 SP21)

Where is it now

Distance from Sun
35.717 AU
True anomaly
197.14°
Distance from Earth
34.731 AU
As of
15 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 — 0.997 AU from the Sun Earth 2015 SP21 — 35.717 AU from the Sun 2015 SP21
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. 2015 SP21 is 34.731 AU from Earth today (4.8 light-hours).

In the sky

Right ascension
01h 05m 21s
Declination
+01° 19′ 50″
Constellation
Cetus
Distance from Earth
34.73 AU
Elongation from the Sun
171.14° — near opposition — up most of the night

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
32.442 AU
Eccentricity
0.1068
Inclination
38.03°
Orbital period
184.8 years
Perihelion
28.977 AU
Aphelion
35.907 AU
Longitude of ascending node
22.26°
Argument of periapsis
154.64°
Epoch · J2000
2457285.5
Orbit class · TNO
Trans-Neptunian object
Earth MOID · 10,901.3 LD
28.0115 AU
Tisserand (Jupiter)
4.072

Orbit quality

Orbit very uncertain — the object may be effectively lost (uncertainty code 9).

Observations used
18
Data arc
2 days
First observed
18 September 2015
Last observed
20 September 2015
Residual RMS
0.09 ″
Solution · Otto Matic
15 April 2021

Visual & observation

Absolute magnitude (H)
7.74

Discovery & classification

TNO

Sources