13 Egeria

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13 Egeria
13 Egeria VLT (2021), deconvolved.pdf
Discovery
Discovered by Annibale de Gasparis
Discovery site Naples Obs.
Discovery date2 November 1850
Designations
(13) Egeria
Pronunciation /ɪˈɪəriə/ [1]
Named after
Egeria
Main belt
Adjectives Egerian
Symbol Egeria symbol (bold).svg (historical)
Orbital characteristics [2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc 60342 days (165.21 yr)
Aphelion 2.7927  AU (417.78  Gm)
Perihelion 2.36115 AU (353.223 Gm)
2.57690 AU (385.499 Gm)
Eccentricity 0.083726
4.14 yr (1510.9 d)
Average orbital speed
18.56 km/s
261.863°
0° 14m 17.736s / day
Inclination 16.539°
43.239°
80.294°
Earth  MOID 1.43999 AU (215.419 Gm)
Jupiter  MOID 2.35966 AU (353.000 Gm)
TJupiter 3.364
Physical characteristics
Dimensionsc/a = 0.76±0.06 [3]
214.8×192 [4]
Mean diameter
202±3 km [3]
207.6 ± 8.3 km (IRAS) [2]
Mean radius
103.82 ± 4.15 km
Mass (9.2±2.1)×1018 kg [3]
(15.9±4.4)×1018 kg [lower-alpha 1] [5]
Mean density
2.13±0.49 g/cm3 [3]
3.4±1.0 g/cm3 [5]
Equatorial surface gravity
≈0.0580 m/s2
Equatorial escape velocity
≈0.1098 km/s
0.2935 d [6]
(7.045 h) [2]
0.087 [3]
0.0825 ± 0.007 [2] [7]
Temperature ~174 K
G-type asteroid [2]
9.71 to 12.46 [8]
6.74 [2]

    Egeria (minor planet designation: 13 Egeria) is a large main-belt G-type asteroid. [9] It was discovered by Annibale de Gasparis on November 2, 1850. Egeria was named by Urbain Le Verrier, whose computations led to the discovery of Neptune, after the mythological nymph Egeria of Aricia, Italy, the wife of Numa Pompilius, second king of Rome. [10]

    Contents

    The historical symbol for Egeria was a buckler. It is in the pipeline for Unicode 17.0 as U+1CEC6 𜻆 ( Egeria symbol (fixed width).svg ). [11] [12]

    OCCULT4 visualization of 13 Egeria occultation event of January 22, 2008 20080122 13EgeriaOccultationProfile.png
    OCCULT4 visualization of 13 Egeria occultation event of January 22, 2008

    Egeria occulted a star on January 8, 1992. Its disc was determined to be quite circular (217×196 km). On January 22, 2008, it occulted another star, and this occultation was timed by several observers in New Mexico and Arizona, coordinated by the IOTA Asteroid Occultation Program. [4] The result showed that Egeria presented an approximately circular profile to Earth of 214.8×192 km, well in agreement with the 1992 occultation.[ citation needed ] It has also been studied by radar. [13]

    In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty. [14] Spectral analysis of Egeria shows it to be unusually high in water content, 10.5–11.5% water by mass. [15] This makes Egeria a prominent candidate for future water-mining ventures.

    A three-dimensional model of 13 Egeria based on its light curve 13Egeria (Lightcurve Inversion).png
    A three-dimensional model of 13 Egeria based on its light curve

    See also

    Notes

    1. (8.0 ± 2.2) × 10−12M

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    References

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    5. 1 2 James Baer, Steven Chesley & Robert Matson (2011) "Astrometric masses of 26 asteroids and observations on asteroid porosity." The Astronomical Journal, Volume 141, Number 5
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