C/2021 U4 (Leonard)

COMETComet

ILLUSTRATION FROM PERIHELION 1.79 AU · ECCENTRICITY 0.959

[

OVERVIEW

] COMET

C/2021 U4 (Leonard) is a comet. It orbits the Sun at a mean distance of 43.96 .

WHAT IT IS: Comet
HOW FAR: 43.96
ONE ORBIT TAKES: 290

[

OBSERVING

] FROM WHERE YOU ARE

What it takes to see C/2021 U4 (Leonard) for yourself. Everything in this part of the page is worked out for a real horizon, a real night and the equipment you say you have.

WHERE IT IS NOW

[

CATALOG DATA

] 11 FIELDS

The raw catalogue values, as the source published them, with the error bars where one was published — sorted by what each set of figures is about rather than by the order they happened to be stored in.

THE ORBIT

The shape of the path, where the object sits on it, and the instant those figures were true of. An orbit is a fit to observations and drifts away from the real one either side of its epoch.

Orbital period: 290.2 ±3500
Eccentricity: ±0.00088
Inclination: 152.88
Longitude of ascending node: 241.8
Argument of perihelion: 237.29 ±0.013
Mean anomaly: 359.81
Element epoch: 2459514.5000
Perihelion passage: 2459570.4700
Minimum distance from Earth's orbit: 0.921
Orbit class: COM

WHEN IT WAS FOUND

Who first saw it, from where, and by what method.

First observed: 2021-09-16

[

ALSO KNOWN AS

] 2 DESIGNATIONS

Comet 2021 U4
Comet C/2021 U4 (Leonard)

[

LOOK IT UP ELSEWHERE

] 1 SERVICE

Each link carries the identifier printed beside it. Nothing on this page is a measurement of our own, so a number that disagrees with one of these is worth reporting — and a service that has never catalogued this object under this name will say so plainly.

JPL Small-Body DatabaseC/2021 U4
The orbit these elements were taken from, with its uncertainty, its close approaches and every observation behind the fit.

[

CITE THIS PAGE

] DR1

This page is live and its numbers move when an upstream refreshes, so the citation names the release the rows belong to rather than the day you read them. The release itself is frozen, republished as a bundle, and is what a data-availability statement should point at.

PLAIN TEXT

SpaceCatalog. C/2021 U4 (Leonard) [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/c-2021-u4-leonard

BIBTEX

@misc{spacecatalog_c-2021-u4-leonard,
  author       = {{SpaceCatalog}},
  title        = {{C/2021 U4 (Leonard)}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/c-2021-u4-leonard},
  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from JPL Small-Body Database.}
}

The values above were taken from JPL Small-Body Database — Public domain (NASA/JPL). Citing this page does not replace citing that catalogue.

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