7 Iris

7 Iris
	Iris imaged by the Very Large Telescope in 2017
Discovery
Discovered by	John Russell Hind
Discovery date	August 13, 1847
Designations
MPC designation	(7) Iris
Pronunciation	/ˈaɪrɪs/
Named after	Īris
Minor planet category	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)
Semi-major axis	2.387 AU (357.1 million km)
Eccentricity	0.22977
Orbital period (sidereal)	3.69 a (1346.8 d)
Average orbital speed	19.03 km/s
Mean anomaly	207.9°
Inclination	5.519°
Longitude of ascending node	259.5°
Time of perihelion	4 April 2025
Argument of perihelion	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	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; 199.83±10 km (IRAS)
Flattening	0.42
Surface area	538460 km2
Volume	37153500 km3
Mass	(13.5±2.3)×1018 kg(13.75±1.3)×1018 kg
Mean density	3.26±0.74 g/cm3; 2.7±0.3 g/cm3
Equatorial surface gravity	0.08 m/s²
Equatorial escape velocity	0.131 km/s
Synodic rotation period	7.138843 h (0.2974518 d)
Equatorial rotation velocity	25.4 m/s
Geometric albedo	0.279; 0.2766±0.030
Temperature	~171 K; max: 275 K (+2°C)
Spectral type	S
Apparent magnitude	6.7 to 11.4
Absolute magnitude (H)	5.64
Angular diameter	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 et al. (2020) Volume uncertainty of (7) Iris shape models from disk-resolved images. Monthly Notices of the Royal Astronomical Society, 499: 3, pp. 4545–4560
^ ^a ^b ^c ^d ^e P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
^ 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]}

Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

[Hanus2019-1] ^ ^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.

[2] "iris". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)

[3] "iridian". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)

[jpldata-4] "JPL Small-Body Database Browser: 7 Iris" (2023-07-08 last obs.). Jet Propulsion Laboratory. Retrieved 18 September 2023.

[Iris-POE-5] "AstDyS-2 Iris Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. Retrieved 1 October 2011.

[Kaasalainen2002-6] 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.

[7] Dudziński et al. (2020) Volume uncertainty of (7) Iris shape models from disk-resolved images. Monthly Notices of the Royal Astronomical Society, 499: 3, pp. 4545–4560

[VLT-8] P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56

[Pasachoff1983-11] 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.

[bright2006-12] "Bright Minor Planets 2006". Minor Planet Center. Retrieved 21 May 2008.^{[permanent dead link]}

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