Upon its discovery, both de Gasparis and Gould labelled Egeria as a new planet.[11][14] However, by the mid-1800s, the classification and terminology of the asteroids were quickly evolving.[15] Soon after Egeria's discovery, other astronomers described it as an "asteroid"[16] or a "minor planet".[17]:25 Throughout the latter half of the 19th century, the terms "asteroid" and "minor planet" became favored,[15] although some publications continued to label Egeria and other asteroids as planets.[15][18]:42
In 1851, de Gasparis announced his chosen symbol for Egeria—that of a buckler. However, Gould had apparently not seen the announcement, and in an 1852 table of asteroid symbols he left Egeria's blank.[19]:8[16] No mention of a star was made, though in 1852 John Russell Hind included one in his drawn symbol for Egeria: (U+1CEC6 in Unicode 17.0). The symbol is sometimes depicted with a round form (),[19]:8 though only Hind's form is in the Unicode pipeline.[20] As the number of asteroids assigned a symbol grew in number through the mid-1800s, the practicality of assigning each a unique astronomical symbol was questioned. In 1851, astronomer Johann Franz Encke proposed an alternative system of a number—denoting the object's order of discovery—inscribed in a circle. For Egeria, this would be ⑬.[15][16] This system was quickly adopted by astronomers, though eventually astronomers switched from an inscribed circle to parentheses and eventually a bare number[15]—hence (13) Egeria or 13 Egeria in modern notation.[1][3]
Physical properties
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 (217×196km). 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 214.8×192km, well in agreement with the 1992 occultation.[citation needed] It has also been studied by radar.[21]
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.[22] Spectral analysis of Egeria shows it to be unusually high in water content, 10.5–11.5% water by mass.[23]
A three-dimensional model of 13 Egeria based on its light curve
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
↑ Hind, John Russel (1852). An Astronomical Vocabulary: Being an Explanation of All Terms in Use Amongst Astronomers at the Present Day. John W. Parker and Son. ISBN978-1120148056.{{cite book}}: ISBN / Date incompatibility (help)
↑ Airy, George Biddell (1869). "Horizontal and Vertical Diameters and Right Ascensions and North Polar Distances of the Sun, Moon and Planets, Deduced from the Observations, and Compared with the Nautical Almanac". Greenwich Observations in Astronomy, Magnetism and Meteorology Made at the Royal Observatory. 2. 29: D31 –D63. Bibcode:1869GOAMM..29D..31A.
↑ 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, vol.19, pp.405–406, Bibcode:1988LPI....19..405G.
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