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Egeria (minor planet designation: 13 Egeria) is a large main-belt G-type asteroid.[7] 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.[8]

13 Egeria Astronomical symbol of 13 Egeria
13Egeria (Lightcurve Inversion).png
A three-dimensional model of 13 Egeria based on its light curve
Discovered byAnnibale de Gasparis
Discovery date2 November 1850
MPC designation(13) Egeria
Pronunciation/ɪˈɪəriə/ i-JEER-ee-ə
Named after
Main belt
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 0
Observation arc60342 days (165.21 yr)
Aphelion2.7927 AU (417.78 Gm)
Perihelion2.36115 AU (353.223 Gm)
2.57690 AU (385.499 Gm)
4.14 yr (1510.9 d)
18.56 km/s
0° 14m 17.736s / day
Earth MOID1.43999 AU (215.419 Gm)
Jupiter MOID2.35966 AU (353.000 Gm)
Physical characteristics
207.6 ± 8.3 km (IRAS)[1]
Mean radius
103.82 ± 4.15 km
Mass1.63×1019 kg[3]
Mean density
3.46±0.79 g/cm³[3]
Equatorial surface gravity
≈0.0580 m/s²
Equatorial escape velocity
≈0.1098 km/s
0.2935 d[4]
(7.045 h)[1]
0.0825 ± 0.007[1][5]
Temperature~174 K
G-type asteroid[1]
9.71 to 12.46[6]
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.[2] 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.[9]

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.[10] Spectral analysis of Egeria shows it to be unusually high in water content, 10.5–11.5% water by mass.[11] This makes Egeria a prominent candidate for future water-mining ventures.

See alsoEdit


  1. ^ a b c d e f "JPL Small-Body Database Browser: 13 Egeria" (2008-11-04 last obs). Retrieved 8 April 2016.
  2. ^ a b Timerson, Brad. "IOTA Asteroid Occultation Results for 2008". Archived from the original on 2014-04-16. Retrieved 2010-01-19. (Chords) Archived 2014-04-16 at the Wayback Machine
  3. ^ a b Jim Baer (2008). "Recent Asteroid Mass Determinations". Personal Website. Retrieved 2008-11-28.
  4. ^ "Lightcurves and map data on numbered asteroids N° 1 to 52225". AstroSurf. Archived from the original on 2005-11-27. Retrieved 2008-11-03.
  5. ^ "Asteroid Data Archive". Planetary Science Institute. Archived from the original on 2006-05-23. Retrieved 2008-11-03.
  6. ^ apmag 9.71 (2061-Nov-06) to 12.46 (1990-Mar-12) JPL Horizons daily output for 1950 to 2099
  7. ^ Rivkin, A. S.; J. K. Davies; S. L. Ellison; L. A. Lebofsky. "High-resolution 2.5–3.5 M Observations of C-, B- and G-class asteroids" (PDF). Retrieved 2008-04-20.
  8. ^ Schmadel, Lutz D. (2003). Dictionary of minor planet names. 1 (5th ed.). Berlin Heidelberg New York: Springer-Verlag. p. 16. ISBN 3-540-00238-3.
  9. ^ "Radar-Detected Asteroids and Comets". NASA/JPL Asteroid Radar Research. Retrieved 2011-10-30.
  10. ^ Gradie, J.; Flynn, L. (March 1988), "A Search for Satellites and Dust Belts Around Asteroids: Negative Results", Abstracts of the Lunar and Planetary Science Conference, 19, pp. 405–406, Bibcode:1988LPI....19..405G.
  11. ^

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