7 Iris
Iris (minor planet designation: 7 Iris) is a large main-belt asteroid and possible remnant planetesimal orbiting the Sun between Mars and Jupiter. It is the fourth-brightest object in the asteroid belt. 7 Iris is classified as an S-type asteroid, meaning that it has a stony composition.
Iris imaged by the Very Large Telescope in 2017 | |
| Discovery | |
|---|---|
| Discovered by | John Russell Hind |
| Discovery date | August 13, 1847 |
| Designations | |
| (7) Iris | |
| Pronunciation | /ˈaɪrɪs/ |
Named after | Īris |
| Main belt | |
| Adjectives | Iridian /ɪˈrɪdiən, aɪ-/ |
| Symbol | (historical) |
| Orbital characteristics | |
| Epoch 13 September 2023 (JD 2453300.5) | |
| Aphelion | 2.935 AU (439.1 million km) |
| Perihelion | 1.838 AU (275.0 million km) |
| 2.387 AU (357.1 million km) | |
| Eccentricity | 0.22977 |
| 3.69 a (1346.8 d) | |
Average orbital speed | 19.03 km/s |
| 207.9° | |
| Inclination | 5.519° |
| 259.5° | |
| 4 April 2025 | |
| 145.4° | |
| Earth MOID | 0.85 AU (127 million km) |
| Proper orbital elements | |
Proper semi-major axis | 2.3862106 AU |
Proper eccentricity | 0.2125516 |
Proper inclination | 6.3924857° |
Proper mean motion | 97.653672 deg / yr |
Proper orbital period | 3.6865 yr (1346.493 d) |
Precession of perihelion | 38.403324 arcsec / yr |
Precession of the ascending node | −46.447128 arcsec / yr |
| Physical characteristics | |
| Dimensions | c/a = 0.58±0.07 268 km × 234 km × 180 km ± (5 km × 4 km × 6 km) 225 km × 190 km × 190 km |
Mean diameter | 199±10 km 214±5 km 200±10 km (IRAS) |
| 538460 km2 | |
| Volume | 37153500 km3 |
| Mass | (13.75±1.3)×1018 kg |
Mean density | 3.2±0.74 g/cm3 2.7±0.3 g/cm3 |
Equatorial surface gravity | 0.08 m/s² |
Equatorial escape velocity | 0.131 km/s |
| 7.138843 h (0.2974518 d) | |
Equatorial rotation velocity | 25.4 m/s |
| 0.279 0.277 | |
| Temperature | ~171 K max: 275 K (+2°C) |
| S | |
| 6.7 to 11.4 | |
| 5.51 | |
| 0.32" to 0.07" | |
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