| Orbital characteristics 1 | |
|---|---|
| Orbit type | Main belt |
| Semimajor axis | 2.770 AU |
| Perihelion distance | 2.115 AU |
| Aphelion distance | 3.426 AU |
| Orbital period | 4.61 years |
| Inclination | 1.39° |
| Eccentricity | 0.237 |
| Physical characteristics 1 | |
| Diameter | 73.22 km |
| Rotation period | 14.208 hours |
| Spectral class | C |
| Abs. magnitude | 9.49 |
| Albedo 4 | 0.053 |
| History 2 | |
| Discoverer | P. P. Henry, 1877 |
177 Irma is a fairly large and dark Main belt asteroid.
It was discovered by brothers Paul Henry and Prosper Henry on November 5, 1877. Paul was credited for this discovery.
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