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79360 Sila–Nunam

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79360 Sila–Nunam
Sila–Nunam imaged by theHubble Space Telescopein 2004
Discovery
Discovered byJ. X. Luu
D. C. Jewitt
C. A. Trujillo
J. Chen [1]
Discovery siteMauna Kea Obs.
Discovery date4 February 1997
Designations
(79360) Sila–Nunam
Pronunciation/ˈsiːləˈnuːnəm/[2]
1997 CS29
TNO(cubewano)[3][4]
AdjectivesSilaupian, Nunaupian[5]
Orbital characteristics[6]
Epoch13 January 2016 (JD2457400.5)
Uncertainty parameter3
Observation arc6940 days (19.00 yr)
Aphelion44.8452AU(6.70875Tm)
Perihelion43.3862 AU (6.49048 Tm)
44.1157 AU (6.59961 Tm)
Eccentricity0.016536
293.02yr(107026d)
331.884°
0.00336367°/day
Inclination2.240951°
304.34152°
≈ 20 October 2055[7]
±3 months
222.597°
Knownsatellites1 at 2,777 ± 19 km (1,725 ± 10 mi)[8][9]
EarthMOID42.3938 AU (6.34202 Tm)
JupiterMOID37.9599 AU (5.67872 Tm)
Physical characteristics
Dimensions≈250±30 km(Sila)
≈235±28 km(Nunam)
(335+41
−42kmcombined)[8][9][10]
Mass1.084 ± 0.022×1019kg (combined)[9]
0.72+0.37
−0.22g/cm3
300.24h(12.510d)
12.50995 ± 0.00036 d[11]
0.086+0.026
−0.017[8]
Temperature~42K(−384°F)
U−B=0.73[8]
B−V=1.08[8][12]
V−R=0.66[12]±0.04[8]
B−R=1.74[8]
V−I=1.25±0.03[8]
R−J=1.4[8]
V−J=2.06±0.03[8]
J−H=0.38±0.08[8]
V−H=2.45±0.08[8]
21.54–21.78 (2014–2015)
(combined) 5.5,[12]
(individual) 6.2 & 6.3 (diff. = 0.12),[8]
5.2[6]

79360 Sila–Nunam(provisional designation1997 CS29) is a cold[9]classical Kuiper belt object(cubewano) andbinary systemmade up of components of almost equal size, called Sila and Nunam, orbiting beyondNeptunein theSolar System.The name of the system is the combined names of the two bodies, Sila and Nunam.[13]

Discovery[edit]

Sila–Nunam was discovered on 4 February 1997 byJane X. Luu,David C. Jewitt,Chad Trujillo,andJun Chenat theMauna Kea Observatory,Hawaii, and given the provisional designation1997 CS29.It was resolved as a binary system inHubbleobservations of 22 October 2002 byDenise C. StephensandKeith S. Nolland announced on 5 October 2005.

Name[edit]

The two components are named afterInuit deities.Sila"air" (Iñupiaqsiḷa[siʎə],Inuktitutsila) is the Inuit god of the sky, weather, and life force. Nuna "earth" (Iñupiaq amn Inuktitutnuna-m[nunəm])[14]is the Earth goddess, in some traditions Sila's wife. Nuna created the land animals and, in some traditions, the Inuit (in other traditions Sila created the first people out of wet sand). Sila breathed life into the Inuit.[6]

Orbit[edit]

Sila–Nunam is a dynamically cold classical system (cubewano). It orbits very close to 4:7mean-motion resonancewithNeptune.[10]

Physical characteristics[edit]

In 2010, thermal flux from Sila–Nunam in thefar-infraredwas measured by theHerschel Space Telescope.As a result, its size, while it was assumed to be a single body, was estimated to lie within the range of 250 to 420 km (155 to 260 mi).[10]Now that it is known to be a binary system, one body 95% the size of the other, the diameters are estimated to be 243 and 230 kilometres (151 and 143 mi).

Sila–Nunam is very red in visible light and has a flat featureless spectrum in thenear-infrared.[15][16]There are no water ice absorption bands in its near-infrared spectrum, which resembles that ofIxion.[17]

Sila–Nunam experiences periodic changes in brightness with the full period, which is equal to the orbital binary period (see below). The light curve is double peaked with the secondary period equal to half of the full period. The rotation of both components of the system is synchronously locked with the orbital motion and both bodies are elongated with their long axes pointing to each other.[11]From 2009 to 2017 Sila–Nunam experienced mutual occultation events.[9]

Double system[edit]

Sila and Nunam are so close in size (within 5%) that they may be thought of as a double cubewano. Sila is approximately 250 km in diameter and Nunam 236 km. Their albedo is about 9%. They orbit at a distance of 2,777 ± 19 km (1,726 ± 12 mi) every 12.51 days:[9][11]

Semi-major axis: 2,777 ± 19 km
Orbital period: 12.50995 ± 0.00036 d
Eccentricity: 0.020 ± 0.015°
Inclination: 103.51 ± 0.39°

Each has apparently been resurfaced with ejecta from impacts on the other.[18]

References[edit]

  1. ^"List of Transneptunian Objects".IAU Minor Planet Center.Archived fromthe originalon 15 October 2008.Retrieved2 August2010.
  2. ^There is no established pronunciation of these names in English, but this is perhaps the easiest way to say them. Depending on dialect and accent, the Inuit language vowelsiandumay be similar to Englishsealandnoonor tosillandnook.Theacan vary in a way reminiscent of how the 'a' in English "an" does (that is, from the 'a' ofsofato the 'a' ofcat). Likewise, the stressed syllable varies, asInuit languagesdo not have distinctive stress. Thus a wide range of English pronunciations can approximateEskimo–Aleut languages.
  3. ^"MPEC 2009-R09:Distant Minor Planets (2009 SEPT. 16.0 TT)".IAU Minor Planet Center. 4 September 2009.Retrieved4 October2009.
  4. ^Marc W. Buie."Orbit Fit and Astrometric record for 79360"(2 February 2009 using 142 observations). SwRI (Space Science Department).Retrieved4 October2009.
  5. ^See Mallon (2000)Inuktitut Linguistics for Technocrats: Morphology
  6. ^abc"JPL Small-Body Database Browser: 79360 Sila-Nunam (1997 CS29)"(2014-01-28 last obs).Retrieved25 March2016.
  7. ^JPL HorizonsObserver Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is3-sigma.)
  8. ^abcdefghijklm"(79360) Sila-Nunam".Wm. Robert Johnston.11 January 2012. Archived fromthe originalon 19 July 2012.Retrieved12 January2012.
  9. ^abcdefW.M. Grundy; S.D. Benecchi; D.L. Rabinowitz; et al. (2012). "Mutual events in the Cold Classical transneptunian binary system Sila and Nunam".Icarus.220:74–83.arXiv:1204.3923.Bibcode:2012Icar..220...74G.doi:10.1016/j.icarus.2012.04.014.
  10. ^abcMuller, T.G.; Lellouch, E.; Stansberry, J.; et al. (2010). ""TNOs are Cool": A survey of the trans-Neptunian region I. Results from the Herschel science demonstration phase (SDP) ".Astronomy and Astrophysics.518:L146.arXiv:1005.2923.Bibcode:2010A&A...518L.146M.doi:10.1051/0004-6361/201014683.
  11. ^abcDavid L. Rabinowitz; Susan D. Benecchi; William M. Grundy; Anne J. Verbiscer (2014). "The rotational light curve of (79360) Sila–Nunam, an eclipsing binary in the Kuiper Belt".Icarus.236:72–82.arXiv:1404.0244.Bibcode:2014Icar..236...72R.doi:10.1016/j.icarus.2014.03.046.
  12. ^abcStephen C. Tegler."Kuiper Belt Object Magnitudes and Surface Color".Archived fromthe originalon 1 September 2006.Retrieved1 August2010.
  13. ^Sila–Nunam Mutual Events(Lowell)
  14. ^For some reason,Nunamincludes thesubject/possessivesuffix -m, whileSiladoes not. There is no such distinction in Inuit. E.g.nuna-m-iis 'on land' whilesila-m-iis 'outside' ( "in the air" ).
  15. ^Grundy, W.M.; Buie, M.W.; Spencer, J. R. (2005). "Near-Infrared Spectrum of Low-Inclination Classical Kuiper Belt Object (79360) 1997 CS29".The Astronomical Journal.130(3): 1299–1301.Bibcode:2005AJ....130.1299G.doi:10.1086/431958.
  16. ^Fornasier, S.; Barucci, M.A.; de Bergh, C.; et al. (2009). "Visible spectroscopy of the new ESO large programme on trans-Neptunian objects and Centaurs: final results".Astronomy and Astrophysics.508(1): 457–465.arXiv:0910.0450.Bibcode:2009A&A...508..457F.doi:10.1051/0004-6361/200912582.
  17. ^Boehnhardt, H.; Bagnulo, S.; Muinonen, S.; et al. (2004)."Surface characterization of 28978 Ixion (2001 KX76)".Astronomy and Astrophysics.415(2): L21–L25.Bibcode:2004A&A...415L..21B.doi:10.1051/0004-6361:20040005.
  18. ^Rabinowitz, et al. (2009). "Evidence for Recent Resurfacing of the Binary Kuiper Belt Object 1997 CS29".

External links[edit]

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