722 Frieda

722 Frieda (prov. designation: A911 UN or 1911 NA) is a bright background asteroid and slow rotator from the inner regions of the asteroid belt. It was discovered by Austrian astronomer Johann Palisa at the Vienna Observatory on 18 October 1911.[1] The stony S-type asteroid has a notably long rotation period of 131.1 hours and measures approximately 9 kilometers (6 miles) in diameter. It was named after Frieda Hillebrand, daughter of Austrian astronomer Karl Hillebrand (1861–1939), and grand-daughter of Edmund Weiss (1837–1917) who had been the director of the discovering observatory.[3]

722 Frieda
Modelled shape of Frieda from its lightcurve
Discovery [1]
Discovered byJ. Palisa
Discovery siteVienna Obs.
Discovery date18 October 1911
Designations
(722) Frieda
PronunciationGerman: [ˈfʁiːdaː][2]
Named after
Frieda Hillebrand,[3]
daughter and grand-daughter of:
Karl Hillebrand (1861–1939)
Edmund Weiss (1837–1917)
A911 UN · 1926 GR
1946 SH · 1911 NA
Orbital characteristics [4]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc109.52 yr (40,002 d)
Aphelion2.4858 AU
Perihelion1.8575 AU
2.1717 AU
Eccentricity0.1447
3.20 yr (1,169 d)
47.845°
0° 18m 28.8s / day
Inclination5.6371°
45.668°
257.23°
Physical characteristics
Mean diameter
131.1±0.2 h[11]
S (SMASS-I)[6]

    Orbit and classification

    Located in the region of the Flora family (402),[11][12] the largest family of stony asteroids, Frieda is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[5][6][7] It orbits the Sun in the inner asteroid belt at a distance of 1.9–2.5 AU once every 3 years and 2 months (1,169 days; semi-major axis of 2.17 AU). Its orbit has an eccentricity of 0.14 and an inclination of 6° with respect to the ecliptic.[4] The body's observation arc begins at Heidelberg Observatory on 19 January 1912, or three months after its official discovery observation by Johann Palisa at Vienna Observatory.[1]

    Naming

    According to Alexander Schnell, this minor planet was named after Frieda Hillebrand, daughter of Austrian astronomer and professor at Graz University, Karl Hillebrand (1861–1939). Frieda is also the grand-daughter of astronomer Edmund Weiss (1837–1917), who was director of the Vienna Observatory (1877–1908) where this asteroid was discovered. The naming citation was not mentioned in The Names of the Minor Planets by Paul Herget in 1955.[3] Palisa also named asteroid 794 Irenaea after Frieda's mother, Irene Hillebrand (née Weiss).[13]

    Physical characteristics

    In the SMASS-I classification by Xu (1995), Frieda is a common, stony S-type asteroid.[6]

    Rotation period

    In April 2019, a rotational lightcurve of Frieda was obtained for the first time from 12 nights of photometric observations by American amateur astronomer Tom Polakis at the Command Module Observatory (V02) in Arizona. Lightcurve analysis gave a rotation period of 131.1±0.2 hours with a high brightness variation of 0.45±0.05 magnitude (U=2).[11]

    Diameter and albedo

    According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE) and the Japanese Akari satellite, Frieda measures (8.257±0.073) and (11.43±0.23) kilometers in diameter and its surface has an albedo of (0.435±0.069) and (0.201±0.009), respectively.[8][9][10]

    The Collaborative Asteroid Lightcurve Link adopts Petr Pravec's revised WISE-data, with an albedo of 0.2721 and a diameter of 8.794 kilometers based on an absolute magnitude of 12.31.[12] Alternative mean-diameters published by the WISE team include (8.835±0.044 km), (9.19±0.22 km) and (10.51±2.46 km) with a corresponding albedo of (0.3309±0.3309), (0.252±0.025) and (0.23±0.10).[6][12]

    References
    1. "722 Frieda (A911 UN)". Minor Planet Center. Retrieved 16 June 2020.
    2. (German Names)
    3. Schmadel, Lutz D. (2007). "(722) Frieda". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 69. doi:10.1007/978-3-540-29925-7_723. ISBN 978-3-540-00238-3.
    4. "JPL Small-Body Database Browser: 722 Frieda (A911 UN)" (2019-09-15 last obs.). Jet Propulsion Laboratory. Retrieved 16 June 2020.
    5. "Asteroid 722 Frieda – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 16 June 2020.
    6. "Asteroid 722 Frieda". Small Bodies Data Ferret. Retrieved 16 June 2020.
    7. Zappalà, V.; Bendjoya, Ph.; Cellino, A.; Farinella, P.; Froeschle, C. (1997). "Asteroid Dynamical Families". NASA Planetary Data System: EAR-A-5-DDR-FAMILY-V4.1. Retrieved 16 June 2020.} (PDS main page)
    8. Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; et al. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System. Bibcode:2016PDSS..247.....M. Retrieved 16 June 2020.
    9. Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121.
    10. 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. Retrieved 16 June 2020. (online, AcuA catalog p. 153)
    11. Polakis, Tom (October 2019). "Photometric Observations of Seventeen Minor Planets" (PDF). Minor Planet Bulletin. 46 (4): 400–406. Bibcode:2019MPBu...46..400P. ISSN 1052-8091.
    12. "LCDB Data for (722) Frieda". Asteroid Lightcurve Database (LCDB). Retrieved 16 June 2020.
    13. Schmadel, Lutz D. (2007). "(794) Irenaea". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 74. doi:10.1007/978-3-540-29925-7_795. ISBN 978-3-540-00238-3.
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