(79360) Sila
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Asteroid (79360) Sila |
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|---|---|
| Properties of the orbit ( animation ) | |
| Orbit type | Cubewano |
| family | |
| Major semi-axis | 43,959 AU |
| eccentricity | 0.014 |
| Perihelion - aphelion | 43,329 AU - 44,589 AU |
| Inclination of the orbit plane | 2.2 ° |
| Length of the ascending node | 304.4 ° |
| Argument of the periapsis | 234 ° |
| Time of passage of the perihelion | December 2047 |
| Sidereal period | 291.46 ± 0.02 a |
| Mean orbital velocity | 4.492 km / s |
| Physical Properties | |
| Medium diameter | 248 km |
| Dimensions | 1.084 ± 0.022 · 10 19 (system) kg |
| Albedo | 0.117 ± 0.035 / 0.024 (system) |
| Medium density | 0.72 + 0.37-0.23 (System) g / cm³ |
| Rotation period | 300 h 14 min 24 s |
| Absolute brightness | 5.3 (system) mag |
| Spectral class | B-V = 1.08 V-R = 0.66 |
| history | |
| Explorer |
Jane X. Luu David C. Jewitt Chadwick A. Trujillo Jun Chen |
| Date of discovery | February 3, 1997 |
| Another name | 1997 CS 29 |
| Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items. | |
(79360) Sila is a trans-Neptunian object in the Kuiper belt that is classified as Cubewano . Since Sila has a companion of almost the same size called Nunam , this system is also known as the double asteroid system (79360) Sila-Nunam .
Discovery and naming
Sila was discovered on February 3, 1997 by a team of astronomers from the California Institute of Technology in Pasadena consisting of Jane X. Luu , David C. Jewitt , Chadwick A. Trujillo and Jun Chen at the Mauna Kea Observatory in Hawaii . The asteroid was initially given the preliminary designation 1997 CS 29 .
On January 9, 2012, Sila and Nunam received the official name, named after Inuit gods. Sila ("spirit") is the Inuit god of heaven, weather and life force. Nunam is the earth goddess, in some traditions as Sila's wife. Nunam created the land animals and, in some traditions, the Inuit people . In other traditions, it was Sila who created the first humans out of damp sand. Sila breathed life into the Inuit.
Since its discovery, the double planetoid has been observed through various telescopes such as the Hubble and Herschel space telescopes, as well as Earth-based telescopes. In January 2018, there were 338 observations over a period of 19 years from 18 oppositions.
Track properties
Orbit
Sila orbits the sun on a slightly elliptical orbit between 43.328 AU and 44.589 AU from its center. The orbit eccentricity is only 0.014, the orbit is 2.248 ° inclined to the ecliptic . It will next go through its perihelion at the turn of the year 2047/2048. In January 2018 it was 43.5 AU from the Sun.
The orbital period of Sila is 291.46 years. Overall, these orbital elements resemble those of Quaoar (287.53 years orbital period).
Local train response
Sila is near a 7: 4 resonance with Neptune . Therefore it is classified as Cubewano and not as a resonant KBO at both the MPC and DES . An object of 7: 4 resonance is for example (469306) 1999 CD 158 .
Physical Properties
size
The diameter of Sila is 248 km, with its companion Nunam being only 5% smaller at 236 km. Measurements in the far infrared range by the Herschel space telescope initially showed a diameter of 250 to 420 km, but for a single body.
internal structure
The extremely low system density of 0.72 g / cm³, which is far below that of water, indicates that water ice must be predominant on both bodies, which is not sufficient to explain the low density, since even pure ice is present 0.91 g / cm³ is even more dense. It can therefore be assumed that both bodies must have cavities inside. (→ Rubble Piles )
surface
In visible light, Sila and Nunam are very red and have a flat spectrum with no near-infrared features that shows no water ice absorptions, which is similar to the spectrum of Ixion . It appears that the surfaces of both components have been renewed by ejecta from impacts on the other body. The surface temperature is around −231 ° C (42 K ).
moon
On October 22, 2002, another team of astronomers headed by Keith S. Noll discovered with the Hubble Space Telescope that Sila has a natural companion that is almost the same size. In terms of size, this system is therefore very similar to the L 5 Jupiter Trojan system Patroclus - Menoetius , the components of which are approximately half the diameter. The two components of the system have a double-bound rotation, so they constantly face the same side. They orbit each other on an approximately circular retrograde orbit with a major semi-axis of 2777 ± 19 km. There were repeated mutual occultations between 2009 and 2017.
See also
Web links
- 1997 CS 29 in listing (Distant Minor Planets) of the Minor Planet Center
- How many dwarf planets are there in the outer solar system? Current list of the largest TNOs from Mike Brown
Individual evidence
- ↑ v ≈ π * a / period (1 + sqrt (1-e²))
- ↑ a b c d W. M. Grundy, SD Benecchi, DL Rabinowitz, SB Porter, LH Wasserman, BA Skiff, KS Noll, AJ Verbiscer, MW Buie, SW Tourtellotte, DC Stephens, HF Levison: Mutual events in the Cold Classical transneptunian binary system Sila and Nunam . In: Icarus . 220, No. 1, July 2012, pp. 74-83. arxiv : 1204.3923 . bibcode : 2012Icar..220 ... 74G . doi : 10.1016 / j.icarus.2012.04.014 .
- ^ A b David L. Rabinowitz, Susan D. Benecchi, William M. Grundy, Anne J. Verbiscer: The rotational light curve of (79360) Sila-Nunam, an eclipsing binary in the Kuiper Belt . In: Icarus . 236, July 1, 2014, pp. 72–82. arxiv : 1404.0244 . bibcode : 2014Icar..236 ... 72R . doi : 10.1016 / j.icarus.2014.03.046 .
- ↑ List Of Transneptunian Objects at the IAU Minor Planet Center
- ↑ (79360) Sila-Nunam in the Small-Body Database of the Jet Propulsion Laboratory (English). Retrieved February 2, 2018.
- ↑ (79360) Sila at the IAU Minor Planet Center (English). Accessed February 2, 2018.
- ↑ (79360) Sila-Nunam in the database of the "Asteroids - Dynamic Site" (AstDyS-2, English). Retrieved February 2, 2018.
- ↑ Brian G. Marsden: MPEC 2009-R09: DISTANT MINOR PLANETS (2009 SEPT 16.0 TT.) . In: IAU Minor Planet Center . September 16, 2009. Retrieved February 2, 2018.
- ^ Marc W. Buie: Orbit Fit and Astrometric record for 79360 . SwRI (Space Science Department). Retrieved February 2, 2018.
- ↑ TG Mueller, E. Lellouch, J. Stansberry, C. Kiss, P. Santos-Sanz, E. Vilenius, S. Protopapa, R. Moreno, M. Mueller, A. Delsanti, R. Duffard, S. Fornasier, O. Groussin, AW Harris, F. Henry, J. Horner, P. Lacerda, T. Lim, M. Mommert, JL Ortiz, M. Rengel, A. Thirouin, D. Trilling, A. Barucci, J. Crovisier, A. Doressoundiram, E. Dotto, PJ Gutierrez, OR Hainaut, P. Hartogh, D. Hestroffer, M. Kidger, L. Lara, B. Swinyard, N. Thomas: “TNOs are Cool”: A survey of the trans- Neptunian region I. Results from the Herschel science demonstration phase (SDP) . In: Astronomy and Astrophysics . 518, July 16, 2010, p. L146. arxiv : 1005.2923 . bibcode : 2010A & A ... 518L.146M . doi : 10.1051 / 0004-6361 / 201014683 .
- ↑ David L. Rabinowitz, B. Schaefer, M. Schaefer, S. Tourtellotte: Evidence for Recent Resurfacing of the Binary Kuiper Belt Object 1997 CS29 . In: American Astronomical Society, DPS meeting . No. 41, id. 65.09, September 2009. bibcode : 2009DPS .... 41.6509R .