![]() Iris imaged by the Very Large Telescope in 2017[1] | |
Discovery | |
---|---|
Discovered by | John Russell Hind |
Discovery date | 13 August 1847 |
Designations | |
(7) Iris | |
Pronunciation | /ˈaɪrɪs/[2] |
Named after | Īris |
Main belt | |
Adjectives | Iridian /ɪˈrɪdiən, aɪ-/[3] |
Symbol | ![]() |
Orbital characteristics[4] | |
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)[4] |
Proper orbital elements[5] | |
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 | 268 km × 234 km × 180 km ± (5 km × 4 km × 6 km)[1] 225 km × 190 km × 190 km[6] |
199±10 km[7][8] 214±5 km[1] 199.83±10 km (IRAS)[4] | |
Flattening | 0.42[a] |
538460 km2[b] | |
Volume | 37153500 km3[b] |
Mass | (13.5±2.3)×1018 kg[8](13.75±1.3)×1018 kg[1] |
Mean density | 3.26±0.74 g/cm3[8] 2.7±0.3 g/cm3[1] |
Equatorial surface gravity | 0.08 m/s² |
Equatorial escape velocity | 0.131 km/s |
7.138843 h (0.2974518 d)[1] | |
Equatorial rotation velocity | 25.4 m/s[b] |
0.279[8] 0.2766±0.030[4] | |
Temperature | ~171 K max: 275 K (+2°C) |
S | |
6.7[9][10] to 11.4 | |
5.64[4] | |
0.32" to 0.07" | |
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.
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