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9 Metis

From Simple English Wikipedia, the free encyclopedia
For the moon of Jupiter, see Metis (moon).
9 Metis Astronomical symbol for 9 Metis
Discovered byA. Graham
Discovery dateApril 25, 1848
1974 QU2
Main belt
Orbital characteristics
Epoch July 14, 2004 (JD 2453200.5)
Aphelion400.548 Gm (2.678 AU)
Perihelion313.556 Gm (2.096 AU)
357.052 Gm (2.387 AU)
1346.815 d (3.69 a)
19.21 km/s
Physical characteristics
Dimensions235×195×140 km[1][2]
Mass~9×1018 kg
Mean density
~2.7 g/cm³[3]
~0.070 m/s²
~0.11 km/s
0.2116 d (5.078 h)[4]
Albedo0.243 (geometric)[5]
Temperature~173 K
max: 282 K (+9° C)[6]
Spectral type
8.1[8] to 11.83
0.23" to 0.071"

9 Metis is one of the biggest main belt asteroids. It is made of silicates and metallic nickel-iron, and may be the core remnant of a big asteroid that was destroyed by an ancient collision.[9]

Discovery and naming[change | change source]

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

Metis was found by Andrew Graham on April 25, 1848; it was his only asteroid discovery.[10] It is also the only asteroid to have been found as a result of observations from Ireland. Its name comes from the mythological Metis, a Titaness and Oceanid, daughter of Tethys and Oceanus.[11] The name Thetis was also considered and rejected (it would later devolve to 17 Thetis).

Characteristics[change | change source]

Metis' direction of rotation is unknown at present.

Hubble space telescope images[2][12] and lightcurve analyses[1] are in agreement that Metis has a non-spherical stretched shape with one pointed and one broad end.[1][12] Radar observations suggest the presence of a significant flat area,[13] in agreement with the shape model from lightcurves.

What the surface is made of has been estimated as 30-40% metal-bearing olivine and 60-70% Ni-Fe metal.[9]

Light curve data on Metis led to an assumption that it could have a moon. However, subsequent observations failed to confirm this.[14][15] Later searches with the Hubble Space Telescope in 1993 found no moons.[12]

Occultations[change | change source]

Metis has been seen to occult stars no less than 5 times.[16]

References[change | change source]

  1. 1.0 1.1 1.2 J. Torppa et al., Shapes and rotational properties of thirty asteroids from photometric data Archived 2015-11-06 at the Wayback Machine, Icarus Vol. 164, p. 346 (2003).
  2. 2.0 2.1 A. D. Storrs et al., A closer look at main belt asteroids 1: WF/PC images, Icarus Vol. 173, p. 409 (2005).
  3. G. A. Krasinsky et al., Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).
  4. "PDS lightcurve data". Archived from the original on 2006-06-14. Retrieved 2007-12-17.
  5. "MSX Infrared minor planet survey (at PDS)". Archived from the original on 2005-02-17. Retrieved 2007-12-17.
  6. 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).
  7. "asteroid lightcurve data file (March 2001)". Archived from the original on 2010-01-17. Retrieved 2007-12-17.
  8. Donald H. Menzel and Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. p. 391. ISBN 0-395-34835-8.
  9. 9.0 9.1 M. S. Kelley and M. J. Gaffey, 9 Metis and 113 Amalthea: A Genetic Asteroid Pair, Icarus Vol. 144, p. 27 (2000).
  10. Graham, A.; New Planet, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 6 (dated April 14, 1848!), p. 146 (signed April 29, 1848; the discovery was first announced on April 27)
  11. Graham, A.; Metis, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 7 (dated May 12, 1848), pp. 147 – 150)
  12. 12.0 12.1 12.2 "Hubble Space Telescope observations" (PDF). Archived from the original (PDF) on 2008-10-30. Retrieved 2007-12-17.
  13. 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).
  14. research at IMCCE Archived 2002-06-12 at the Wayback Machine (in French)
  15. "other" reports of asteroid companions
  16. W. M. Kissling et al., The diameter of (9) Metis from the Occultation of SAO 190531, Proceedings of the Astronomical Society of Australia Vol 9, p. 150 (1991).

Other websites[change | change source]