9 Metis

Image:Moon and Asteroids 1 to 10.svg. 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.Graham, A.; [http://adsabs.harvard.edu/abs/1848MNRAS...8..146G 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) 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.{{cite web |date=10 October 2008 |title=Amateur Astronomer Becomes Second Ever to Discover Asteroid from Ireland, After 160 Years |publisher=International Year of Astronomy in Ireland |url=http://astronomy2009.ie/news/second_irish_amateur_astron.html |access-date=2 March 2009|archive-url=https://web.archive.org/web/20110721122044/http://astronomy2009.ie/news/second_irish_amateur_astron.html|archive-date=21 July 2011}} Its name comes from the mythological Metis, a Titaness and Oceanid, daughter of Tethys and Oceanus.Graham, A.; [http://adsabs.harvard.edu/abs/1848MNRAS...8..148. Metis], Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 7 (dated 12 May 1848), pp. 147–150 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 𜻃 (12px).{{cite web |url=https://www.unicode.org/L2/L2023/23207-historical-asteroids.pdf |title=Unicode request for historical asteroid symbols |last1=Bala |first1=Gavin Jared |last2=Miller |first2=Kirk |date=18 September 2023 |website=unicode.org |publisher=Unicode |access-date=26 September 2023 |quote=}}{{cite web |url=https://unicode.org/alloc/Pipeline.html |title=Proposed New Characters: The Pipeline |author=Unicode |date= |website=unicode.org |publisher=The Unicode Consortium |access-date=6 November 2023 |quote=}}

file:9Metis (Lightcurve Inversion).png-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.J. Torppa et al., [http://www.rni.helsinki.fi/~mjk/thirty.pdf Shapes and rotational properties of thirty asteroids from photometric data], Icarus Vol. 164, p. 346 (2003). 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.{{Citation needed|date=June 2007}}

Hubble Space Telescope imagesA. D. Storrs et al., A closer look at main-belt asteroids 1: WF/PC images, Icarus Vol. 173, p. 409 (2005).[http://web.media.mit.edu/~win/hstpub.pdf Hubble Space Telescope observations] {{webarchive|url=https://web.archive.org/web/20081030022816/http://web.media.mit.edu/~win/hstpub.pdf |date=30 October 2008 }} and lightcurve analyses are in agreement that Metis has an irregular elongated shape with one pointed and one broad end. Radar observations suggest the presence of a significant flat area,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). 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.

Light curve data on Metis led to an assumption that it could have a satellite. However, subsequent observations failed to confirm this.[http://www.bdl.fr/observateur/binast/binary_ast.php research at IMCCE] {{webarchive|url=https://web.archive.org/web/20020612093733/http://www.bdl.fr/observateur/binast/binary_ast.php |date=12 June 2002 }} (in French)[http://www.johnstonsarchive.net/astro/asteroidmoonsq.html "other" reports of asteroid companions] Later searches with the Hubble Space Telescope in 1993 found no satellites.

Metis was once considered to be a member of an asteroid family known as the Metis family,J. G. Williams, Asteroid Families – An Initial Search, Icarus Vol. 96, p. 251 (1992). 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. 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. Coincidentally, both Metis and Amalthea have namesakes among Jupiter's inner moons.

In 1984 an occultation of a star produced seven chords that Kristensen used to derive an ellipsoidal profile of 210×170 km.{{cite journal

|last1=Kissling |first1=W.M

|last2=Blow |first2=G. L.

|last3=Allen |first3=W. H.

|last4=Priestley |first4=J.

|last5=Riley |first5=P.

|last6=Daalder |first6=P.

|last7=George |first7=M.

|title=The Diameter of 9 Metis from the Occultation of SAO:190531

|journal=Proceedings of the Astronomical Society of Australia

|volume=9 |pages=150–152 |date=1991

|issue=1

|bibcode=1991PASA....9..150K

|doi=10.1017/S1323358000025352

|s2cid=117689158

}} On 6 August 1989, Metis occulted a magnitude 8.7 star producing five chords suggesting a diameter of 173.5 km. Observations of an occultation on 11 February 2006, produced only two chords indicating a minimum diameter 156 km.{{cite web

|title = Occultation of TYC 0862-00695-1 by (9) Metis 2006 February 11

|publisher = Royal Astronomical Society of New Zealand

|url = http://occsec.wellington.net.nz/planet/2006/results/060211_Metis.htm

|access-date = 6 December 2008

|url-status = dead

|archive-url = https://web.archive.org/web/20080827155624/http://occsec.wellington.net.nz/planet/2006/results/060211_Metis.htm

|archive-date = 27 August 2008

|df = dmy-all

}} [http://occsec.wellington.net.nz/planet/2006/results/060211_Metis_PlotColour.gif (Chords)] {{webarchive|url=https://web.archive.org/web/20110724205049/http://occsec.wellington.net.nz/planet/2006/results/060211_Metis_PlotColour.gif |date=24 July 2011 }} All three of these occultations fit the ellipsoid 222×182×130 km suggested by Baer.

On 7 March 2014, Metis occulted the star HIP 78193 (magnitude 7.9) over parts of Europe and the Middle East.[http://www.asteroidoccultation.com/2014_03/0307_9_32274.htm Asteroid Occulations] {{webarchive|url=https://web.archive.org/web/20140306184634/http://www.asteroidoccultation.com/2014_03/0307_9_32274.htm |date=6 March 2014 }}[http://www.asteroidoccultation.com/2014_03/0307_9_32274_MapE.gif Map] {{webarchive|url=https://web.archive.org/web/20140306185840/http://www.asteroidoccultation.com/2014_03/0307_9_32274_MapE.gif |date=6 March 2014 }}

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{{Reflist|30em}}

• [http://www.rni.helsinki.fi/~mjk/thirty.pdf shape model deduced from lightcurve]
• [http://adsabs.harvard.edu//full/seri/MNRAS/0008//0000146.000.html "Notice of discovery of Metis", MNRAS 8 (1848) 146]
• [https://web.archive.org/web/20040823231519/http://www.eaas.co.uk/news/metis.html Irish Astronomical History: Markree Castle Observatory and The Discovery of the Asteroid Metis]
• [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=9 JPL Ephemeris]
• {{cite web |title=Elements and Ephemeris for (9) Metis |publisher=Minor Planet Center |url=http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=b2011&o=00009 |url-status=dead |archive-url=https://web.archive.org/web/20160304051845/http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=b2011&o=00009 |archive-date=4 March 2016 }} (displays Elong from Sun and V mag for 2011)
• [http://www.astrode.de/metis2014d.htm Globe of 9 Metis]
• {{AstDys|9}}
• {{JPL small body}}

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Category:Flora asteroids

Metis

Metis

Category:S-type asteroids (Tholen)

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