130 Elektra

Elektra (minor planet designation: 130 Elektra) is a large outer main-belt asteroid. It was discovered on 17 February 1873, by astronomer Christian Peters at Litchfield Observatory, New York, and named after Electra, an avenger in Greek mythology.

130 Elektra
VLT image of Elektra (filtered, center) and its moons (left)
Discovery[1]
Discovered byC. H. F. Peters
Discovery siteLitchfield Obs.
Discovery date17 February 1873
Designations
(130) Elektra
Pronunciation/ɪˈlɛktrə/[2]
Named after
Electra
Main belt
AdjectivesElektrian /ɪˈlɛktriən/[3]
Orbital characteristics[4][5]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc122.35 yr (44690 d)
Aphelion3.77969 AU (565.434 Gm)
Perihelion2.47815 AU (370.726 Gm)
3.12892 AU (468.080 Gm)
Eccentricity0.20799
5.53 yr (2021.6 d)
128.885°
0° 10m 41.084s / day
Inclination22.8461°
145.401°
236.231°
Known satellitesS/2003 (130) 1
S/2014 (130) 1
Physical characteristics
Dimensions182.25±11.8 km[5]
215×155 ± 12 km[6][7][8][9]
Mass6.6±0.4×1018 kg[10]
1.28±0.10×1019 kg[11][12]
Mean density
1.3 ± 0.3 g/cm3[10]
3.8 ± 0.3 g/cm3[11]
Equatorial surface gravity
0.07 m/s2[13]
Equatorial escape velocity
0.13 km/s[13]
5.225 h (0.2177 d)
0.230103 d (5.52247 h)[14]
157°
-88°[14]
68°
0.0755±0.011[5]
0.076 ± 0.011 [7]
Surface temp. min mean max
Kelvin ~157 251
Celsius -23°
G [15]
7.12[5][7]

    Description
    Lightcurve-based 3D-model of 130 Elektra

    The spectrum of 130 Elektra is of the G type; hence it probably has a Ceres-like composition. Spectral signatures of organic compounds have been seen on Elektra's surface[16] and it displays evidence of aqueous alteration.[17]

    In the late 1990s, a network of astronomers worldwide gathered lightcurve data that was ultimately used to derive the spin states and shape models of 10 new asteroids, including (130) Elektra. The light curve of (130) Elektra forms a double sinusoid while the shape model is elongated and the derived rotation axis is perpendicular to the plane of the ecliptic.[18][19]

    Optical observations have found two satellites of this asteroid. Once the orbits are known, Elektra's mass can be reliably found. The value of 6.6×1018 kg indicates a density of 1.3 ± 0.3 g/cm3. Optical observations have also determined that Elektra's shape is quite irregular, as well as giving indications of albedo differences of 5-15% on its surface.[14]

    Occultations

    Elektra has been observed to pass in front of a dozen stars since 2007, most notably on April 21, 2018 when over 30 mostly citizen astronomers spread across five European countries recorded the sudden drop in light of an 11th magnitude star. The sky-plane plot of the chords reveals a peanut-shaped body, possibly the result of a two-body merger early in the history of the Solar System.

    Shape of Elektra as observed from Europe on April 21, 2018.

    Satellites
    Elektra (brightness muted) and its two moons

    In 2003, a small moon of (130) Elektra was detected using the Keck II telescope. The diameter of the satellite is 4 km and it orbits at a distance of about 1170 km. It was given the provisional designation S/2003 (130) 1. Due to only a few observations to date, its orbit is still relatively loosely constrained.[11] In December 2014 a smaller inner moon, about 2 km across and orbiting Elektra about three times closer than S/2003 (130) 1, was discovered using the SPHERE instrument on the VLT's Melipal (UT3) telescope. It was provisionally named S/2014 (130) 1.[20]

    S/2003 (130) 1
    Discovery[21]
    Discovered byW. J. Merline, P. M. Tamblyn,
    C. Dumas, L. M. Close,
    C. R. Chapman, and F. Menard
    Discovery date15 August 2003
    Designations
    Main belt
    Orbital characteristics[10]
    1318 ± 25 km
    Eccentricity0.13 ± 0.03
    5.258 ± 0.0053 d
    23 m/s
    Inclination3
    Satellite of130 Elektra
    Physical characteristics
    Dimensions7 ± 3 km [14]
    Mass~4×1014 kg [22]
    Equatorial escape velocity
    		~ 4 m/s
    14.5[14]
      S/2014 (130) 1

        References
        1. Discovery Circumstances: Numbered Minor Planets, Minor Planet Centre
        2. "Electra". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
        3. George William Cox (1878) History of Greece
        4. "The Asteroid Orbital Elements Database". astorb. Lowell Observatory.
        5. "130 Elektra". JPL Small-Body Database. NASA/Jet Propulsion Laboratory. Retrieved 12 May 2016.
        6. Based in IRAS mean diameter of 182±12 km, a/b ratio of 1.4 as per the following references
        7. Supplemental IRAS Minor Planet Survey Archived 2009-08-17 at the Wayback Machine
        8. PDS node spin vector database (in particular, the synthetic compiled value of a/b=1.4).
        9. (130) Elektra and S/2003 (130) 1, at Johnston's archive (maintained by W. R. Johnston).
        10. Marchis, Franck; P. Descamps; J. Berthier; D. hestroffer; F. vachier; M. Baek; et al. (2008). "Main Belt Binary Asteroidal Systems With Eccentric Mutual Orbits". Icarus. 195 (1): 295–316. arXiv:0804.1385. Bibcode:2008Icar..195..295M. doi:10.1016/j.icarus.2007.12.010.
        11. 130 Elektra and S/2003 (130) 1 Archived 2007-07-24 at the Wayback Machine, orbit data website maintained by F. Marchis.
        12. Error estimate derived from consideration of and given errors in a and P. See propagation of uncertainty.
        13. On the extremities of the long axis.
        14. F. Marchis; et al. (2006). "Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey". Icarus. 185 (1): 39–63. Bibcode:2006Icar..185...39M. doi:10.1016/j.icarus.2006.06.001. PMC 2600456. PMID 19081813.
        15. PDS node taxonomy database Archived 2009-08-05 at the Wayback Machine
        16. Cruikshank, D. P. & Brown, R. H. (1987). "Organic Matter on Asteroid 130 Elektra". Science. 238 (4824): 183–4. Bibcode:1987Sci...238..183C. doi:10.1126/science.238.4824.183. PMID 17800458.
        17. Fornasier, S.; et al. (February 1999), "Spectroscopic comparison of aqueous altered asteroids with CM2 carbonaceous chondrite meteorites", Astronomy and Astrophysics Supplement, 135: 65–73, Bibcode:1999A&AS..135...65F, doi:10.1051/aas:1999161.
        18. Durech, J.; et al. (April 2007), "Physical models of ten asteroids from an observers' collaboration network", Astronomy and Astrophysics, 465 (1): 331–337, Bibcode:2007A&A...465..331D, doi:10.1051/0004-6361:20066347
        19. Durech, J.; Kaasalainen, M.; Marciniak, A.; Allen, W. H. (2007). "Asteroid brightness and geometry". Astronomy and Astrophysics. 465 (1): 331–337. Bibcode:2007A&A...465..331D. doi:10.1051/0004-6361:20066347.
        20. "Elektra: A New Triple Asteroid". www.eso.org. European Southern Observatory. Retrieved 9 May 2016.
        21. IAUC 8183 Archived 2006-05-01 at the Wayback Machine
        22. Assuming a similar density to the primary.

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