 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 | .svg){kind=small} (historical) |
| 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.
- ^ a b c d e f g Hanuš, J.; Marsset, M.; Vernazza, P.; Viikinkoski, M.; Drouard, A.; Brož, M.; et al. (24 April 2019). "The shape of (7) Iris as evidence of an ancient large impact?". Astronomy & Astrophysics. 624 (A121): A121. arXiv:1902.09242. Bibcode:2018DPS....5040406H. doi:10.1051/0004-6361/201834541. S2CID 119089163.
- ^ "iris". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ "iridian". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ a b c d e "JPL Small-Body Database Browser: 7 Iris" (2023-07-08 last obs.). Jet Propulsion Laboratory. Retrieved 18 September 2023.
- ^ "AstDyS-2 Iris Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. Retrieved 1 October 2011.
- ^ Kaasalainen, M.; et al. (2002). "Models of twenty asteroids from photometric data" (PDF). Icarus. 159 (2): 369–395. Bibcode:2002Icar..159..369K. doi:10.1006/icar.2002.6907.
- ^ Dudziński, G; et al. (14 October 2020). "Volume uncertainty of (7) Iris shape models from disc-resolved images". Monthly Notices of the Royal Astronomical Society. 499 (3): 4545–4560. doi:10.1093/mnras/staa3153. hdl:10261/237568. ISSN 0035-8711.
- ^ a b c d e Vernazza, P.; et al. (October 2021). "VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis". Astronomy & Astrophysics. 654: A56. Bibcode:2021A&A...654A..56V. doi:10.1051/0004-6361/202141781. hdl:10261/263281. ISSN 0004-6361.
- ^ Donald H. Menzel & Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. pp. 391. ISBN 0-395-34835-8.
- ^ "Bright Minor Planets 2006". Minor Planet Center. Retrieved 21 May 2008.[permanent dead link]
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