9 Metis

Template:Short description Template:Distinguish Template:Use dmy dates {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 9 Metis | image = {{#invoke:InfoboxImage|InfoboxImage|image=9 Metis VLT (2021), deconvolved.pdf|upright={{#if:||1.1}}|alt=}} | caption = | headerstyle = {{#if:#D6D6D6|background-color:#D6D6D6|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery

| header10 = {{#if:|Designations|Designations}}

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="jpldata">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

| data21 = | data22 = {{#if:13 September 2023
(JD 2453300.5) |Epoch 13 September 2023
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| header60 = Proper orbital elements<ref name=Metis-POE>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

| label61 = Template:Longitem | data61 = {{#if:2.3864354 |2.3864354 AU}} | label62 = Template:Longitem | data62 = 0.1271833 | label63 = Template:Longitem | data63 = 4.6853629° | label64 = Template:Longitem | data64 = {{#if:97.638314 |97.638314 deg Template:\yr}} | label65 = Template:Longitem | data65 = {{#if:97.638314|{{#expr:360/97.638314 round 5}} yr
({{#expr:365.25*360/97.638314 round 3}} d) }} | label66 = Template:Longitem | data66 = {{#if:38.754973|38.754973 arcsec Template:\yr }} | label67 = Template:Longitem | data67 = {{#if:−41.998090|−41.998090 arcsec Template:\yr}}

| header70 = Template:Anchor{{#if:yes| Physical characteristics|Physical characteristics}}

| label71 = Dimensions | data71 = (222 × 182 × 130) ± 12 km<ref name="Baer2011" /> | label72 = Template:Longitem | data72 = Template:Val<ref name=VLT>P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56</ref>
190±? km (Dunham)<ref name="jpldata" /> | label73 = Template:Longitem | data73 = | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = 0.39Template:Efn | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = | label80 = Mass | data80 = Template:Val<ref name=VLT/>
Template:Val Template:Refn<ref name="Baer2011">James Baer, Steven Chesley & Robert Matson (2011) "Astrometric masses of 26 asteroids and observations on asteroid porosity." The Astronomical Journal, Volume 141, Number 5</ref> | label81 = Template:Longitem | data81 = Template:Val<ref name=VLT/>
Template:Val<ref name="Baer2011"/> | label82 = Template:Longitem | data82 = | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = | label85 = Template:Longitem | data85 = 0.2116 d (5.079 h)<ref name="jpldata" /> | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = | label88 = Template:Longitem | data88 = | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = | label92 = Template:Longitem | data92 = | label93 = {{#if:yes |Template:Longitem |Albedo}} | data93 = 0.18<ref name=VLT/>
0.118<ref name="jpldata" /> | label94 = Temperature | data94 = max: 282 K (+9 °C)<ref name="Lim05">L. F. Lim et al., Thermal infrared (8–13 μm) spectra of 29 asteroids: the Cornell Mid-Infrared Asteroid Spectroscopy (MIDAS) Survey, Icarus Vol. 173, p. 385 (2005).</ref>

| data100 = {{#if:|

Surface temp.	min	mean	max
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| header110 = Atmosphere

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9 Metis is one of the larger main-belt asteroids. It is composed of silicates and metallic nickel-iron, and may be the core remnant of a large asteroid that was destroyed by an ancient collision.<ref name="Kelley00">Template:Cite journal</ref> Metis is estimated to contain just under half a percent of the total mass of the asteroid belt.<ref name="Baer"> {{#invoke:citation/CS1|citation |CitationClass=web }} </ref>

Discovery and namingEdit

File:Moon and Asteroids 1 to 10.svg

The first 10 asteroids profiled against Earth's Moon. 9 Metis is second from right.

Metis was discovered by Andrew Graham on 25 April 1848, at Markree Observatory in Ireland; it was his only asteroid discovery.<ref>Graham, A.; New Planet, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 6 (dated 14 April 1848!), p. 146 (signed 29 April 1848; the discovery was first announced on 27 April)</ref> It also has been the only asteroid to have been discovered as a result of observations from Ireland until 7 October 2008, when, 160 years later, Dave McDonald from observatory J65 discovered (281507) 2008 TM₉.<ref name="Ireland">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Its name comes from the mythological Metis, a Titaness and Oceanid, daughter of Tethys and Oceanus.<ref>Graham, A.; Metis, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 7 (dated 12 May 1848), pp. 147–150</ref> The name Thetis was also considered and rejected (it would later devolve to 17 Thetis).

The historical symbol for Metis was an eye with a star above it. It is in the pipeline for Unicode 17.0 as U+1CEC3 𜻃 (File:Metis symbol (fixed width).svg).<ref name=astunicode>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=pipeline>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

CharacteristicsEdit

File:9Metis (Lightcurve Inversion).png

Lightcurve-based 3D-model of Metis

Metis's direction of rotation is unknown at present, due to ambiguous data. Lightcurve analysis indicates that the Metidian pole points towards either ecliptic coordinates (β, λ) = (23°, 181°) or (9°, 359°) with a 10° uncertainty.<ref name="Torppa03">J. Torppa et al., Shapes and rotational properties of thirty asteroids from photometric data, Icarus Vol. 164, p. 346 (2003).</ref> The equivalent equatorial coordinates are (α, δ) = (12.7 h, 21°) or (23.7 h, 8°). This gives an axial tilt of 72° or 76°, respectively.Template:Citation needed

Hubble Space Telescope images<ref name="Hubble05">A. D. Storrs et al., A closer look at main-belt asteroids 1: WF/PC images, Icarus Vol. 173, p. 409 (2005).</ref><ref name="Hubble99">Hubble Space Telescope observations Template:Webarchive</ref> and lightcurve analyses<ref name="Torppa03" /> are in agreement that Metis has an irregular elongated shape with one pointed and one broad end.<ref name="Torppa03" /><ref name="Hubble99" /> Radar observations suggest the presence of a significant flat area,<ref name="Mitchell95">D. L. Mitchell et al., Radar Observations of Asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda, Icarus Vol. 118, p. 105 (1995).</ref> in agreement with the shape model from lightcurves.

The Metidian surface composition has been estimated as 30–40% metal-bearing olivine and 60–70% Ni-Fe metal.<ref name="Kelley00" />

Light curve data on Metis led to an assumption that it could have a satellite. However, subsequent observations failed to confirm this.<ref>research at IMCCE Template:Webarchive (in French)</ref><ref>"other" reports of asteroid companions</ref> Later searches with the Hubble Space Telescope in 1993 found no satellites.<ref name="Hubble99" />

Family relationshipsEdit

Metis was once considered to be a member of an asteroid family known as the Metis family,<ref name="Williams92">J. G. Williams, Asteroid Families – An Initial Search, Icarus Vol. 96, p. 251 (1992).</ref> but more recent searches for prominent families did not recognize any such group, nor is a clump evident in the vicinity of Metis by visual inspection of proper orbital element diagrams.

However, a spectroscopic analysis found strong spectral similarities between Metis and 113 Amalthea, and it is suggested that these asteroids may be remnants of a very old (at least ~1 Ga) dynamical family whose smaller members have been pulverised by collisions or perturbed away from the vicinity. The putative parent body is estimated to have been 300 to 600 km in diameter (Vesta-sized) and differentiated.<ref name="Kelley00" /> Metis would be the relatively intact core remnant (though smaller than 16 Psyche), and Amalthea a fragment of the mantle, with 90% of the original body unaccounted for.<ref name="Kelley00" /> Coincidentally, both Metis and Amalthea have namesakes among Jupiter's inner moons.

OccultationsEdit

In 1984 an occultation of a star produced seven chords that Kristensen used to derive an ellipsoidal profile of 210×170 km.<ref name="occult">Template:Cite journal</ref> On 6 August 1989, Metis occulted a magnitude 8.7 star producing five chords suggesting a diameter of 173.5 km.<ref name="occult" /> Observations of an occultation on 11 February 2006, produced only two chords indicating a minimum diameter 156 km.<ref name="RASNZ">{{#invoke:citation/CS1|citation |CitationClass=web }} (Chords) Template:Webarchive</ref> All three of these occultations fit the ellipsoid 222×182×130 km suggested by Baer.<ref name="Baer" />

On 7 March 2014, Metis occulted the star HIP 78193 (magnitude 7.9) over parts of Europe and the Middle East.<ref>Asteroid Occulations Template:Webarchive</ref><ref>Map Template:Webarchive</ref>