Editing 7 Iris (section)

==Characteristics==
[[Image:Moon and Asteroids 1 to 10.svg|thumb|left|Size comparison: the first 10 asteroids profiled against Earth's [[Moon]]. Iris is fourth from the right.]]

===Geology===
Iris is an S-type asteroid. The surface is bright and is probably a mixture of [[nickel]]-[[iron]] metals and [[magnesium]]- and iron-[[silicate]]s. Its spectrum is similar to that of [[L chondrite|L]] and [[LL chondrite]]s with corrections for [[space weathering]],<ref name="Ueda2003">{{Cite conference |last1=Ueda |first1=Y. |last2=Miyamoto |first2=M. |last3=Mikouchi |first3=T. |last4=Hiroi |first4=T. |date=March 2003 |title=Surface Material Analysis of the S-type Asteroids: Removing the Space Weathering Effect from Reflectance Spectrum |conference=34th Annual Lunar and Planetary Science Conference |pages=2078 |bibcode=2003LPI....34.2078U}}</ref> so it may be an important  contributor of these [[meteorites]]. Planetary dynamics also indicates that it should be a significant source of meteorites.<ref name="Migliorini">{{cite journal| bibcode=1997A&A...321..652M| first1= F.|last1= Migliorini| title=(7) Iris: a possible source of ordinary chondrites?| journal=Astronomy & Astrophysics| volume= 321| pages=652| date=1997| first2=A.|last2=Manara|first3=A.| last3=Cellino|first4=M.| last4=Di Martino|first5=V.| last5=Zappala|display-authors=1}}
</ref>

Among the [[S-type asteroid]]s, Iris ranks fifth in [[mean diameter]] after [[15 Eunomia|Eunomia]], [[3 Juno|Juno]], [[29 Amphitrite|Amphitrite]] and [[532 Herculina|Herculina]]. Its shape is consistent with an oblate spheroid with a large equatorial excavation, suggesting it is a remnant planetesimal. No collisional family can be associated with Iris, likely because the excavating impact occurred early in the history of the Solar System, and the debris has since dispersed.<ref name="Hanus2019"/>

===Brightness===
[[File:7Iris-LB1-richfield-mag10.jpg|thumb|left|Star rich field showing asteroid Iris ([[apparent magnitude|apmag]] 10.1)]]
Iris's bright surface and small distance from the Sun make it the fourth-brightest object in the [[asteroid belt]] after [[4 Vesta#Visibility|Vesta]], [[Ceres (dwarf planet)#Observations|Ceres]], and [[2 Pallas#Characteristics|Pallas]].  It has a ''[[mean]]'' opposition [[apparent magnitude|magnitude]] of +7.8, comparable to that of [[Neptune#Observation|Neptune]], and can easily be seen with [[binoculars]] at most oppositions. At typical [[opposition (astronomy)|opposition]]s it marginally outshines the larger though darker [[2 Pallas|Pallas]].<ref>{{cite web|last=Odeh |first=Moh'd |url=http://jas.org.jo/ast.html |title=The Brightest Asteroids |publisher=Jordanian Astronomical Society |access-date=2007-07-16 |archive-url=https://web.archive.org/web/20070813224051/http://www.jas.org.jo/ast.html |archive-date=13 August 2007 |url-status=dead }}</ref> But at rare oppositions near perihelion Iris can reach a magnitude of +6.7 (last time on 31 October 2017, reaching a magnitude of +6.9),<ref name="Pasachoff1983" /> which is as bright as Ceres ever gets.

===Surface features===
A study by Hanus et al. using data from the [[Very Large Telescope|VLT]]'s SPHERE instrument names eight craters 20 to 40&nbsp;km in diameter, and seven recurring features of unknown nature that remain nameless due to a lack of consistency and their occurrence on the edge of Iris. The names are Greek names of colors, corresponding to the rainbow as the sign of Iris. It is unknown whether these names are under consideration by the [[IAU]]. The other 7 features are labeled A through G.<ref name="Hanus2019"/>

{| class="wikitable"
|+ Named craters on Iris
|-
! width=100 | Feature !! Pronunciation !! Greek !! Meaning
|-
| Chloros || {{IPAc-en|ˈ|k|l|oʊ|r|ɒ|s}} || [[wikt:χλωρός|χλωρός]] || 'green'
|-
| Chrysos || {{IPAc-en|ˈ|k|r|aɪ|s|ɒ|s}} || [[wikt:χρῡσός|χρῡσός]] || 'gold'
|-
| Cirrhos || {{IPAc-en|ˈ|s|ɪr|ɒ|s}} || [[wikt:κιρρός|κιρρός]] || 'orange'{{refn|κιρρός is variously translated. The OED has 'orange-tawny'.<ref>{{OED|cirrhosis}}</ref> The color coding of the proposers in their crater maps, however, is simply orange.|name=|group=lower-alpha}}
|-
| Cyanos || {{IPAc-en|ˈ|s|aɪ|ə|n|ɒ|s}} || [[wikt:κύανος|κύανος]] || 'blue'
|-
| Erythros || {{IPAc-en|ˈ|ɛr|ɪ|θ|r|ɒ|s}} || [[wikt:ἐρυθρός|ἐρυθρός]] || 'red'
|-
| Glaucos || {{IPAc-en|ˈ|g|l|ɔː|k|ɒ|s}} || [[wikt:γλαυκός|γλαυκός]] || 'grey'{{refn|Or greyish blue-green.|name=|group=lower-alpha}}
|-
| Porphyra|| {{IPAc-en|ˈ|p|ɔr|f|ɪ|r|ə}} || [[wikt:πορφύρα|πορφύρα]] || 'purple'
|-
| Xanthos || {{IPAc-en|ˈ|z|æ|n|θ|ɒ|s}} || [[wikt:ξανθός|ξανθός]] || 'yellow'
|}

===Rotation===
Iris has a rotational period of 7.14 hours. Iris's north pole points towards the [[ecliptic coordinate system|ecliptic coordinates]] (λ, β) estimated to be (18°, +19°) with a 4° uncertainty (Viikinkoski et al. 2017) or (19°, +26°) with a 3° uncertainty (Hanuš et al. 2019). This gives an [[axial tilt]] of 85°,<ref>{{cite book|last=Pearson|first=Richard |title=The History of Astronomy|year=2020|isbn=9780244866501|page=349|publisher=Lulu.com }}</ref> so that on much of each hemisphere, the sun does not set during summer, and does not rise during winter. On an airless body this gives rise to very large temperature differences.