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Ymir (moon)

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Ymir
Discovery image of Ymir taken by the La Silla Observatory in August 2000
Discovery[1]
Discovered byBrett J. Gladman
Discovery siteObservatoire de la Cote d'Azur
Discovery date2000
Designations
Designation
Saturn XIX
Pronunciation/ˈiːmɪər/,[2] /ˈɪmɪər/[3]
Named after
Ymir
S/2000 S 1
AdjectivesYmirian /ɪˈmɪəriən/[a][5]
Orbital characteristics[6]
Epoch 2000 January 1.5
22957100 km
Eccentricity0.337
−3.6 yr (−1315.16 d)
344.3°
Inclination173.1°
61.5°
90.8°
Satellite ofSaturn
GroupNorse group
Physical characteristics[7][8][9]
Dimensions24 km × 22 km × 16 km
19+50%
−30% km
Circumference65 km (equatorial)
−11.92220±0.00002 h
North pole right ascension
280°±20°[b]
North pole declination
70°±10°[b]
Albedo0.06[10]
Spectral type
D/P
21.7[11]
12.3

Ymir /ˈiːmɪər/, or Saturn XIX, is the second-largest retrograde irregular moon of Saturn. It was discovered by Brett J. Gladman, et al. in 2000, and given the temporary designation S/2000 S 1. It was named in August 2003 after Ymir, who in Norse mythology is the ancestor of all the Jotuns or frost giants.[12]

It takes 3.6 Earth years to complete an orbit around Saturn. Of the moons that take more than 3 Earth years to orbit Saturn, Ymir is the largest, at about 19 kilometres (12 miles) in diameter;[11] Ymir is also the second largest member of the Norse group, after Phoebe.[9]

Spectral measurements from Cassini–Huygens show that Ymir is reddish in color, unlike Phoebe's gray color, suggesting a separate origin for this moon. It shows a similar light curve as Siarnaq and has a triangular shape, rotating in a retrograde direction about once every 11.9 hours.[9]

Ymir imaged by the CFHT on 23 September 2000
3D model created based on lightcurve data

Notes

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  1. ^ Because the -r is an inflectional ending, and the oblique stem is Ymi (as in Modern Norse Yme), one might expect the English adjective to be ?Ymian, but that is perhaps too short a word to be easily intelligible.[4]
  2. ^ a b Assuming the north pole is the one pointing north of the invariable plane, in accordance with IAU standards.

References

[edit]
  1. ^ Brian G. Marsden (2000-10-25). "IAUC 7512". IAU. Retrieved 2011-01-08.
  2. ^ "Ymir". Merriam-Webster.com Dictionary. Merriam-Webster.
  3. ^ Merriam-Webster's Encyclopedia of Literature. 1995.
  4. ^ Budd (1898). "Norse Mythology". St. Mary's Hall lectures: and other papers. p. 84.
  5. ^ James Hall III (2015). Moons of the Solar System. p. 107.
  6. ^ Jacobson, R. A. (2007-06-28). "Planetary Satellite Mean Orbital Parameters". JPL/NASA. Retrieved 2008-02-14.
  7. ^ "Ymir (S/2000 S 1) – Tilmann Denk".
  8. ^ Denk, T.; Mottola, S. (2019). Cassini Observations of Saturn's Irregular Moons (PDF). 50th Lunar and Planetary Science Conference. Lunar and Planetary Institute.
  9. ^ a b c Denk, Tilmann; Mottola, Stefano; Tosi, Frederico; Bottke, William F.; Hamilton, Douglas P. (2018). "The Irregular Satellites of Saturn" (PDF). In Schenk, P.M.; Clark, R.N.; Howett, C.J.A.; Verbiscer, A.J.; Waite, J.H. (eds.). Enceladus and the Icy Moons of Saturn. Space Science Series. Vol. 322. Tucson, AZ: The University of Arizona Press. pp. 409–434. Bibcode:2018eims.book..409D. doi:10.2458/azu_uapress_9780816537075-ch020. ISBN 9780816537075.
  10. ^ Nicholson, P. D. (2001), {{citation}}: Missing or empty |title= (help)
  11. ^ a b Sheppard, Scott S. "Saturn's Known Satellites". Department of Terrestrial Magnetism. Retrieved 2008-02-14.
  12. ^ Daniel W. E. Green (2003-08-08). "IAUC 8177: Sats OF (22); Sats OF JUPITER, SATURN, URANUS". IAU. Retrieved 2011-01-08.
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