(120347) Salacia

from Wikipedia, the free encyclopedia
Asteroid
(120347) Salacia
Salacia and Actaea through the Hubble Space Telescope (2006).
Salacia and Actaea through the Hubble Space Telescope (2006).
Properties of the orbit ( animation )
Epoch:  April 27, 2019 ( JD 2,458,600.5)
Orbit type DO (E SDO ) or
CKBO ( hot ),
"Distant Object" 
Major semi-axis 42.057  AU
eccentricity 0.108
Perihelion - aphelion 37.495 AU - 46.618 AU
Inclination of the orbit plane 23.9 °
Length of the ascending node 279.9 °
Argument of the periapsis 310.9 °
Time of passage of the perihelion February 20, 1926
Sidereal period 272 a 8 M
Mean orbital velocity 4.555 km / s
Physical Properties
Medium diameter
Dimensions 4.38 ± 0.16  ·  10 20 Template: Infobox asteroid / maintenance / mass kg
Albedo
Medium density g / cm³
Rotation period 6.09 ± 0.03 h (0.254 d )
Absolute brightness 4.476 ± 0.013 mag
Spectral class C
B-V = 0.820 ± 0.020
VR = 0.470 ± 0.020
VI = 0.870 ± 0.010
history
Explorer Henry G. Roe
Michael E. Brown
Kristina M. Barkume
Date of discovery September 22, 2004
Another name 2004 SB 60
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.

(120347) Salacia (former designation 2004 SB 60 ) is a large trans-Neptunian object in the Kuiper belt , which is classified as Cubewano or an extended Scattered Disc Object (DO) in terms of orbital dynamics . Because of its size, the asteroid is a dwarf planet candidate . Since Salacia has a large companion called Actaea , this system can also be understood as a double asteroid system.

Discovery and naming

Salacia was discovered on September 22, 2004 by a team of astronomers from the California Institute of Technology in Pasadena , consisting of Henry G. Roe, Michael E. Brown and Kristina M. Barkume at the Palomar Observatory . The discovery was announced on May 7, 2005; the asteroid was given the provisional designation 2004 SB 60 and on 19 September 2006 by the IAU , the minor planet number 120347 . Salacia was the sixth discovery of a large TNO and likely dwarf planet by Mike Brown's team of astronomers. Brown's team successively discovered Quaoar and 2002 MS4 (2002), Sedna (2003) and Haumea (2003, controversial), and Orcus . This was also followed by the dwarf planets Eris and Makemake (2005) and Gonggong (2007).

On February 18, 2011, the asteroid was officially named Salacia , after Neptune's wife, the goddess of salt water. The name is probably derived from "salum" (sea or ocean wave). Since the beautiful nymph Salacia was also associated with Venus, the word origin can also be “salax” (horny, in the sexual sense).

After its discovery, Salacia could be identified in photos up to July 25, 1982, which were taken as part of the Digitized Sky Survey at the Siding Spring Observatory ( Australia ), and thus its orbit was calculated more precisely. Since then, the asteroid has been observed through various telescopes such as the Hubble , Herschel and Spitzer Space Telescopes, as well as Earth-based telescopes. In December 2017, there were a total of 124 observations on 14 oppositions over a period of 35 years. The last observation so far was made in August 2018 at the Purple Mountain Observatory ( China ). (As of March 13, 2019)

properties

Orbit

Salacia orbits the sun in a slightly elliptical orbit between 5,540,000,000 km (37.35  AU ) and 6,959,000,000 km (46.55 AU) from its center. The orbital eccentricity is 0.11, the orbit is 23.93 ° inclined to the ecliptic . Currently, Salacia is 40.20 AU from the sun. She passed perihelion for the last time in 1988, so the next perihelion is likely to take place in 2338.

The orbit period of Salacia is 272.75 years. This is comparable to the orbital period of the dwarf planet Haumea (285.5 years) or Quaoar (287.5 years). Although Salacia's orbit inclination is about 24 ° and the orbit elements generally fit, it is not a member of the Haumea family. Currently, Salacia is 44.84 AU from the Sun. She passed through perihelion for the last time in 1926, so the next perihelion should take place in 2198.

The Minor Planet Center classifies Salacia as Cubewano , as a non- SDO and generally as a distant object , while Marc Buie ( DES ) classifies it as an extended SDO (ESDO or DO ).

Size and rotation

It is currently assumed to have a diameter of 866 km, with Salacia currently occupying 35th place in terms of size in the solar system. It is thus somewhat smaller than the dwarf planet Ceres (950 km). This is more than originally assumed, as Salacia was initially thought to be much lighter and the diameter was therefore initially estimated to be between 650 km and 750 km. Other TNOs of this size are 2002 MS 4 and Orcus . Based on a diameter of 866 km, the total area is about 2,356,000 km², which roughly corresponds to the area of Algeria .

Since it can be assumed that Salacia is in hydrostatic equilibrium due to its size and must therefore be largely round, it would have to meet the criteria for classification as a dwarf planet . Mike Brown assumes that Salacia is almost certainly a dwarf planet. According to Gonzalo Tancredi, it is only possibly one; however, in 2010 it was based on a diameter of around 600 km.

Salacia rotates once on its axis every 6 hours and 5.4 minutes. From this it follows that in a Salacia year it performs 393701.9 self- rotations ("days"). However, this is still fraught with uncertainties, as the observation time at that time was insufficient and the error rate is around 30%.

Size comparison of the 10 largest TNOs
Provisions of the diameter for Salacia
year Dimensions km source
2008 554.0 Tancredi
2010 607.0 Tancredi
2011 930.0 ± 210.0 Grundy et al. a.
2012 852.1 Vilenius et al. a.
2012 905.0 ± 103.0 Stansberry et al. a.
2013 854.0 ± 45.0 Fornasier et al. a.
2013 901.0 ± 45.0 Lellouch u. a.
2014 <491.0 Thirouin et al. a.
2015 666.08 LightCurve DataBase
2017 866.0 ± 37.0 Brown et al. a.
2018 921.0 Brown
The most precise determination is marked in bold .

Mass and internal structure

After the discovery of the moon Actaea , the total mass of the system could be determined to 4.38 ± 0.16 ⋅ 10 20 kg, of which Salacia should combine a good 96% because of its three times larger diameter.

Studies of the dark surface of Salacia in the near infrared spectrum indicate that there is not as much water ice on it as originally thought (allegedly below 5%), although the density of 1.29 g / cm³ is close to that of water. According to this, the internal structure of Salacia would still have to consist mainly of water ice, with additions of rock, comparable to the Saturn moon Iapetus or the Uranus moon Miranda . Another possibility would be cavities below the surface, which would explain the low density. However, Salacia is actually too large to have significant porosity and therefore its internal structure is probably differentiated . A rock core with a density of 2.77-3.66 g / cm³ could represent 40 to 65% of the total diameter of Salacia if its water ice mantle is non-porous and 45 to 70% if its mantle has a 10% porosity.

surface

The surface of Salacia, with an extremely weak reflectivity of 3.5%, is much darker than originally assumed, which is why the diameter estimate was initially smaller. It is actually darker than all other TNOs of this size, although there are other similarly dark objects such as 2002 MS 4 (5.1%) and 2003 AZ 84 (6.5%) that are only slightly brighter. The apparent magnitude of Salacia is 20.79  m .

moon

Orbital simulation of Salacia and Actaea.

On September 9, 2006, another team of astronomers headed by Keith S. Noll discovered a natural companion with the Hubble Space Telescope, which is almost exactly ⅓ the diameter of Salacia (290 ± 21 km). This system thus shows strong parallels to the Orcus - Vanth system in terms of orbital elements and proportions , which, however, like all large TNOs, is considerably lighter (albedo 28%); In addition, these two components orbit each other around a third greater distance. In 2067 there will be mutual coverings of Salacias and Actaeas. Since the two components of the system orbit each other relatively closely, the tidal forces have reduced the eccentricity of the lunar orbit to near zero.

The Salacia system at a glance:

Components Physical parameters Path parameters discovery
Surname Throughput
diameter
(km) 		Relative
size
% 		Mass
(kg) 		Major
semi-axis
(km) 		Orbital time
(d) 		eccentricity
 Inclination
to Salacia's
equator 		date
(120347) Salacia
 866.0 100.00 4.38 · 10 20 - - - - September 22, 2004
Actaea
(Salacia I) 		290.0 34.40 1.86 · 10 19 5619 5.4938 0.0084 ? ° July 21, 2006

See also

Web links

Commons : (120347) Salacia  - Collection of images, videos and audio files

Individual evidence

  1. ^ A b Marc W. Buie : Orbit Fit and Astrometric record for 120347 . SwRI (Space Science Department). Retrieved March 8, 2019.
  2. ↑ a b W. Grundy u. a .: Five New and Three Improved Mutual Orbits of Transneptunian Binaries (PDF) . In: Icarus . 213, No. 2, March 14, 2011, pp. 678-692. arxiv : 1103.2751 . bibcode : 2011Icar..213..678G . doi : 10.1016 / j.icarus.2011.03.012 .
  3. ↑ a b MPC : MPEC 2010-S44: Distant Minor Planets (2010 OCT.11.0 TT) . IAU . September 25, 2010. Retrieved March 8, 2019.
  4. ↑ a b c E. Lellouch u. a .: “TNOs are Cool”: A survey of the trans-Neptunian region. IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations (PDF) . In: Astronomy and Astrophysics . 557, No. A60, June 10, 2013, p. 19. bibcode : 2013A & A ... 557A..60L . doi : 10.1051 / 0004-6361 / 201322047 .
  5. ^ Wm. R. Johnston: List of Known Trans-Neptunian Objects . Johnston's Archives. October 7, 2018. Retrieved March 8, 2019.
  6. ↑ a b (120347) Salacia at IAU Minor Planet Center (English) Retrieved March 8, 2019.
  7. ↑ v ≈ π * a / period (1 + sqrt (1-e²))
  8. ↑ a b c Mike Brown : The Density of Mid-sized Kuiper Belt Objects from ALMA Thermal Observations . In: The Astronomical Journal . 154/1, No. 19, July 7, 2017, p. 7. arxiv : 1702.07414 . bibcode : 2017AJ .... 154 ... 19B . doi : 10.3847 / 1538-3881 / aa6346 .
  9. ↑ a b c d e f J. Stansberry u. a .: Physical Properties of Trans-Neptunian Binaries (120347) Salacia – Actaea and (42355) Typhon – Echidna (PDF) . In: Icarus . 219, April 5, 2012, pp. 676-688. bibcode : 2012Icar..219..676S . doi : 10.1016 / j.icarus.2012.03.029 .
  10. ↑ a b Data refer to the whole Salacia-Actaea system
  11. ↑ a b c d e S. Fornasier u. a .: “TNOs are Cool”: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of nine bright targets at 70-500 µm (PDF) . In: Astronomy and Astrophysics . 555, No. A15, June 19, 2013, p. 22. arxiv : 1305.0449v2 . bibcode : 2013A & A ... 555A..15F . doi : 10.1051 / 0004-6361 / 201321329 .
  12. ↑ A. Thirouin et al. a .: Short-term variability of a sample of 29 trans-Neptunian objects and Centaurs . In: Astronomy and Astrophysics . 522, No. A93, April 27, 2010, p. 43. arxiv : 1004.4841 . bibcode : 2010A & A ... 522A..93T . doi : 10.1051 / 0004-6361 / 200912340 .
  13. ↑ a b LCDB Data for (120348) Salacia . MinorPlanetInfo. 2015. Accessed March 8, 2019.
  14. ↑ a b H. Boehnhardt u. a .: Photometry of Transneptunian Objects for the Herschel Key Program “TNOs are Cool” . In: Earth, Moon, and Planets . 114, No. 1-2, November 2014, pp. 35-57. bibcode : 2014EM & P..114 ... 35B . doi : 10.1007 / s11038-014-9450-x .
  15. ↑ O. Hainaut et al. a .: Colors of minor bodies in the outer solar system. II. A statistical analysis revisited (PDF) . In: Astronomy and Astrophysics . 546, No. A115, September 10, 2012, p. 20. arxiv : 1209.1896 . bibcode : 2012A & A ... 546A.115H . doi : 10.1051 / 0004-6361 / 201219566 .
  16. ↑ MPC : MPEC 2005-J28: 2004 SB60 . IAU . May 7, 2005. Retrieved March 8, 2019.
  17. ^ Daniel WE Green: IAUC 8751: (120347) 2004 SB_60; 2006gi, 2006gj; V733 Cep . Central Bureau for Astronomical Telegrams. September 19, 2006. Retrieved March 8, 2019.
  18. ↑ (120347) Salacia in the Small-Body Database of the Jet Propulsion Laboratory (English). Retrieved March 8, 2019. Template: JPL Small-Body Database Browser / Maintenance / Alt
  19. ↑ MPC : MPEC List Of Centaurs and Scattered-Disk Objects . IAU . Retrieved March 8, 2019.
  20. ↑ a b Mike Brown : How many dwarf planets are there in the outer solar system? . CalTech . November 12, 2018. Retrieved March 8, 2019.
  21. ^ A b G. Tancredi: Physical and dynamical characteristics of icy “dwarf planets” (plutoids) (PDF) . In: IAU (Ed.): Icy Bodies of the Solar System: Proceedings IAU Symposium No. 263, 2009 . 2010. doi : 10.1017 / S1743921310001717 . Retrieved March 8, 2019.
  22. ^ G. Tancredi, S. Favre: DPPH List . In: Dwarf Planets and Plutoid Headquarters, from Which are the dwarfs in the solar system? . August. Retrieved March 8, 2019.
  23. ↑ E. Vilenius et al. a .: “TNOs are Cool”: A survey of the trans-Neptunian region VI. Herschel / PACS observations and thermal modeling of 19 classical Kuiper belt objects (PDF) . In: Astronomy and Astrophysics . 541, No. A94, April 4, 2012, p. 17. arxiv : 1204.0697 . bibcode : 2012A & A ... 541A..94V . doi : 10.1051 / 0004-6361 / 201118743 .
  24. ↑ A. Thirouin et al. a .: Rotational properties of the binary and non-binary populations in the Trans-Neptunian belt . In: Astronomy and Astrophysics . 569, No. A3, July 5, 2014, p. 20. arxiv : 1407.1214 . bibcode : 2014A & A ... 569A ... 3T . doi : 10.1051 / 0004-6361 / 201423567 .
  25. ↑ E. Schaller et al. a .: Detection of Additional Members of the 2003 EL61 Family via Infrared Spectroscopy (PDF) . In: The Astronomical Journal . 684/2, 2008/08/01, p. L107. arxiv : 0808.0185 . bibcode : 2008ApJ ... 684L.107S . doi : 10.1086 / 592232 .
  26. ↑ (120347) Salacia in the database of the "Asteroids - Dynamic Site" (AstDyS-2, English). Retrieved October 13, 2019.
  27. ^ Wm. Robert Johnston: (120347) Salacia and Actaea . September 20, 2014. Accessed March 8, 2019.
  28. ^ W. Grundy: Salacia (120347 2004 SB60) . Lowell Observatory . December 6, 2015. Accessed March 8, 2019.