894 Erda

894 Erda (prov. designation: A918 LA or 1918 DT) is a bright background asteroid from the outer regions of the asteroid belt. It was discovered on 4 June 1918, by German astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory.[1] The X-type asteroid has a short rotation period of 4.7 hours and measures approximately 37 kilometers (23 miles) in diameter. It was likely named after a character in Wagner's Der Ring des Nibelungen, "Erda", who is the goddess of wisdom, fate and Earth, borrowed from the Norse sagas, and referring to both Urðr and Jörð in Norse mythology.[2]

894 Erda
Discovery [1]
Discovered byM. F. Wolf
Discovery siteHeidelberg Obs.
Discovery date4 June 1918
Designations
(894) Erda
Named after
Erda, goddess in Wagner's Der Ring des Nibelungen
(Norse mythology)[2]
A918 LA · 1973 QB
A907 JC · 1907 JC
A912 HD · 1912 HD
1918 DT
main-belt [1][3] · (outer)
background [4][5]
Orbital characteristics [3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc112.73 yr (41,173 d)
Aphelion3.4642 AU
Perihelion2.7752 AU
3.1197 AU
Eccentricity0.1104
5.51 yr (2,013 d)
150.20°
0° 10m 44.04s / day
Inclination12.733°
190.61°
116.33°
Physical characteristics
Mean diameter
  • 28.309±1.544 km[6]
  • 36.54±1.8 km[7]
  • 37.84±0.45 km[8]
4.6897±0.0003 h[9]
  • 0.2300±0.025[7]
  • 0.232±0.007[8]
  • 0.319±0.060[6]
X (S3OS2)[5][10]
9.7[1][3]

    Orbit and classification

    Erda is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[4][5] It orbits the Sun in the outer main-belt at a distance of 2.8–3.5 AU once every 5 years and 6 months (2,013 days; semi-major axis of 3.12 AU). Its orbit has an eccentricity of 0.11 and an inclination of 13° with respect to the ecliptic.[3] On 14 May 1907, the body's observation arc begins as A907 JC (1907 JC ) at Heidelberg; just two nights after its first observation, and more than 11 years prior to its official discovery observation.[1]

    Naming

    According to The Names of the Minor Planets by Paul Herget in 1955, and adopted by Lutz Schmadel in the Dictionary of Minor Planet Names, this minor planet was named after the Norse goddess described as the "incarnation of the nature", and as "a seer who knows the origin and the destination of all things" (H 87).[2]

    The discoverer, Max Wolf, likely adopted the name from Wagner's opera cycle Der Ring des Nibelungen, which is loosely based on figures from the Norse sagas. In Wagner's Ring, the character Erda (Wagner), named after the Old High German word for "Earth", is the goddess of wisdom, fate and Earth. She is the world's wisest woman, the mother of the three Norns and of the valkyrie (shieldmaid) Brunhild, whose father is the norse chief god Odin (Wotan). Wagner, in turn, adopted the name from the treatise Deutsche Mythologie by Jacob Grimm (1785–1863) and other sources. Erda combines attributes of both, Urðr (wisdom and fate) and Jörð (the personification of Earth).

    Physical characteristics

    In both the Tholen- and SMASS-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Erda is an X-type asteroid.[5][10]

    Rotation period

    In June 2006, a rotational lightcurve of Erda was obtained from photometric observations by David Higgins at Hunters Hill Observatory (E14), Australia, and by Rui Gonçalves at Linhaceira Observatory (938) in Portugal. Lightcurve analysis gave a well-defined rotation period of 4.6897±0.0003 hours with a brightness variation of 0.27±0.02 magnitude, significantly higher than previous observations had measured (U=3). The observers also found no indication of a previously speculated companion.[9]

    The result supersedes observations from July 2001, when both Robert Stephens and Laurent Bernasconi determined a period of 4.69±0.01 and 4.69±0.05 hours with an amplitude of 0.05±0.01 and 0.06±0.03 magnitude, respectively.[11][12]

    Diameter and albedo

    According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Erda measures (28.309±1.544), (36.54±1.8) and (37.84±0.45) kilometers in diameter and its surface has an albedo of (0.319±0.060), (0.2300±0.025) and (0.232±0.007), respectively.[6][7][8] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1942 and a diameter of 36.26 kilometers based on an absolute magnitude of 9.6.[13] An alternative mean-diameter measurement published by the WISE team gives (51.074±1.760 km) with an albedo of (0.120±0.007).[5][13] On 17 April 2010, an asteroid occultation gave a best-fit ellipse dimension of 36.00 × 36.0 kilometers, while a second observation on 15 September 2014, measured an ellipse of 38.00 × 38.0 kilometers These timed observations are taken when the asteroid passes in front of a distant star.[5]

    References
    1. "894 Erda (A918 LA)". Minor Planet Center. Retrieved 25 February 2020.
    2. Schmadel, Lutz D. (2007). "(894) Erda". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. pp. 80–81. doi:10.1007/978-3-540-29925-7_895. ISBN 978-3-540-00238-3.
    3. "JPL Small-Body Database Browser: 894 Erda (A918 LA)" (2020-02-01 last obs.). Jet Propulsion Laboratory. Retrieved 25 February 2020.
    4. "Asteroid 894 Erda – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 February 2020.
    5. "Asteroid 894 Erda". Small Bodies Data Ferret. Retrieved 25 February 2020.
    6. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8.
    7. Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 25 February 2020.
    8. Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. (online, AcuA catalog p. 153)
    9. Higgins, David; Goncalves, Rui M. D. (March 2007). "Asteroid Lightcurve Analysis at Hunters Hill Observatory and Collaborating Stations - June-September 2006" (PDF). Minor Planet Bulletin. 34 (1): 16–18. Bibcode:2007MPBu...34...16H. ISSN 1052-8091.
    10. Lazzaro, D.; Angeli, C. A.; Carvano, J. M.; Mothé-Diniz, T.; Duffard, R.; Florczak, M. (November 2004). "S3OS2: the visible spectroscopic survey of 820 asteroids" (PDF). Icarus. 172 (1): 179–220. Bibcode:2004Icar..172..179L. doi:10.1016/j.icarus.2004.06.006. Retrieved 25 February 2020.
    11. Stephens, R. D. (March 2002). "Photometry of 866 Fatme, 894 Erda, 1108 Demeter, and 3443 Letsungdao" (PDF). Minor Planet Bulletin. 29 (1): 2–3. Bibcode:2002MPBu...29....2S. Archived from the original (PDF) on 4 October 2021. Retrieved 25 February 2020.
    12. Behrend, Raoul. "Asteroids and comets rotation curves – (894) Erda". Geneva Observatory. Retrieved 25 February 2020.
    13. "LCDB Data for (894) Erda". Asteroid Lightcurve Database (LCDB). Retrieved 25 February 2020.
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