Trans-Neptunian object

Borasisi

66652 Borasisi (1999 RZ253)

Where is it now

Distance from Sun: 42.803 AU
True anomaly: 80.35°
Distance from Earth: 41.899 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.

Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Borasisi is 41.899 AU from Earth today (5.8 light-hours).

In the sky

Right ascension: 00h 09m 35s
Declination: +00° 25′ 03″
Constellation: Pisces
Distance from Earth: 41.9 AU
Elongation from the Sun: 154.68° — 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.

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How do I find my coordinates?

Google Maps on a computer

Right-click the spot where you'll be observing.
The first line of the menu is the coordinates, e.g. 51.50722, -0.12758 — click it and they're copied.
Paste them above.

Google Maps on a phone

Press and hold the spot to drop a pin.
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.

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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: 43.725 AU
Eccentricity: 0.0847
Inclination: 0.56°
Orbital period: 289.1 years
Perihelion: 40.021 AU
Aphelion: 47.43 AU
Longitude of ascending node: 84.63°
Argument of periapsis: 197.95°
Epoch · J2000: 2461200.5
Orbit class · TNO: Trans-Neptunian object
Earth MOID · 15,179.2 LD: 39.0039 AU
Tisserand (Jupiter): 5.896

Orbit quality

Orbit very well determined (uncertainty code 2).

Observations used: 341
Data arc: 26.12 years
First observed: 8 September 1999
Last observed: 20 October 2025
Residual RMS: 0.62 ″
Solution · Otto Matic: 7 October 2026

Visual & observation

Absolute magnitude (H): 5.85

Discovery & classification

Discovered by: Trujillo, C. A., Luu, J. X., Jewitt, D. C.
Discovery date: 8 September 1999
Discovery site: Mauna Kea

Also named is (66652) I Pabu, discovered 2003 Apr. 23 by K. Noll, D. Stephens, W. Grundy and colleagues using the Hubble Space Telescope. Borasisi and Pabu are the mythical personifications of the sun and moon in the fictional cosmogony of Bokononism described in Kurt Vonnegut's novel <i>Cat's Cradle</i>: “Borasisi, the sun, held Pabu, the moon, in his arms and hoped that Pabu would bear him a fiery child. But poor Pabu gave birth to children that were cold, that did not burn... Then poor Pabu herself was cast away, and she went to live with her favorite child, which was Earth.”

Also known as 66652 · 1999 RZ253

Named TNO

Sources

visual properties: JPL SBDB (lookup)
orbital elements: JPL SBDB