101 Helena
ILLUSTRATION FROM SMASS TYPE S · ALBEDO 0.190 · RADIUS 32.9 KM
OVERVIEW
] ASTEROID101 Helena is a main-belt asteroid. Its absolute magnitude () is 8.39. It orbits the Sun at a mean distance of 2.583 . Its effective radius is 32.92 . It is catalogued as 101 Helena (A868 PA). It was discovered in 1868.
- WHAT IT IS
- Main-belt asteroid
- HOW FAR
- 2.583
- HOW BIG
- 32.92
- HOW BRIGHT IN ITSELF (H)
- ONE ORBIT TAKES
- 4.16
Its average distance from the Sun, not from Earth.
The radius of a ball that would look the same size — the body itself is not round.
How bright it would look from a fixed, standard distance — a measure of the object rather than of the view from here.
One trip round the Sun.
OBSERVING
] FROM WHERE YOU AREWhat it takes to see 101 Helena 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.
CATALOG DATA
] 17 FIELDSThe 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.
WHAT IT IS MADE OF
What the object is in itself, rather than how it happens to look from here.
- Spectral type (SMASS II)
- S
- Rotation period
- 23.08
HOW BRIGHT IT IS
What the light adds up to, measured through one filter at a time. A magnitude is a brightness on a backwards scale — the smaller the number, the brighter the object.
- Albedo
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
- 4.162
- Eccentricity
- Inclination
- 10.19
- Longitude of ascending node
- 343.36
- Argument of perihelion
- 347.73
- Mean anomaly
- 11.14
- Element epoch
- 2461200.5000
- Perihelion passage
- 2461153.5700
- Minimum distance from Earth's orbit
- 1.21
- Orbit class
- MBA
WHEN IT WAS FOUND
Who first saw it, from where, and by what method.
- Discovered by
- Watson, J. C.
- Discovered from
- Ann Arbor
- Discovered on
- 1868-08-15
- First observed
- 1871-03-22
ALSO KNOWN AS
] 3 DESIGNATIONS- Asteroid 101
- Asteroid 101 Helena (A868 PA)
- Common name Helena
LOOK IT UP ELSEWHERE
] 1 SERVICEEach 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 Database101
The orbit these elements were taken from, with its uncertainty, its close approaches and every observation behind the fit.
CITE THIS PAGE
] DR1This 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.
SpaceCatalog. 101 Helena [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/101-helena
@misc{spacecatalog_101-helena,
author = {{SpaceCatalog}},
title = {{101 Helena}},
howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
year = {2026},
url = {https://spacecatalog.org/object/101-helena},
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.