794 Irenaea

794 Irenaea (prov. designation: A914 QB or 1914 VB) is a dark background asteroid from the outer regions of the asteroid belt. It was discovered on 27 August 1914, by Austrian astronomer Johann Palisa at the Vienna Observatory.[1] The presumed C-type asteroid has a rotation period of 9.1 hours and measures approximately 36 kilometers (22 miles) in diameter. It was likely named after Irene Hillebrand, daughter of Austrian astronomer Edmund Weiss (1837–1917).[3]

794 Irenaea
Discovery [1]
Discovered byJ. Palisa
Discovery siteVienna Obs.
Discovery date27 August 1914
Designations
(794) Irenaea
Pronunciation/ɪrɪˈniːə/[2]
Named after
Irene Hillebrand, daughter of Edmund Weiss
(Austrian astronomer )[3]
A914 QB · 1930 KH
1936 QK · 1947 QD
1953 TT2 · 1914 VB
Orbital characteristics [4]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 0
Observation arc83.12 yr (30,360 d)
Aphelion4.0559 AU
Perihelion2.2004 AU
3.1281 AU
Eccentricity0.2966
5.53 yr (2,021 d)
31.160°
0° 10m 41.16s / day
Inclination5.4193°
160.40°
131.27°
Physical characteristics
Mean diameter
9.14±0.01 h[12]
C (assumed)[5]

    Orbit and classification

    Irenaea is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[6][7][8] It orbits the Sun in the outer main-belt at a distance of 2.2–4.1 AU once every 5 years and 6 months (2,021 days; semi-major axis of 3.13 AU). Its orbit has an eccentricity of 0.30 and an inclination of 5° with respect to the ecliptic.[4] The body's observation arc begins at Bergedorf Observatory in Hamburg on 9 December 1915, more than a year after its official discovery observation at Vienna Observatory on 27 August 1914.[1]

    Naming

    According to Alexander Schnell, this minor planet was likely named after Irene Hillebrand, née Weiss, daughter of Austrian astronomer Edmund Weiss (1837–1917), director of the Vienna Observatory, and wife to astronomer Karl Hillebrand (1861–1939). The name received an aea-suffix as "Irene" was already given to asteroid 14 Irene.[3] Palisa also named asteroid 722 Frieda after her daughter, Frieda Hillebrand.[13]

    Physical characteristics

    Irenaea is an assumed, carbonaceous C-type asteroid.[5] The asteroid's low albedo around 0.05 (see below) agrees with this assumption.

    Rotation period

    In May 2008, a rotational lightcurve of Irenaea was obtained from photometric observations by Italian amateur astronomer Silvano Casulli. Lightcurve analysis gave a rotation period of 9.14±0.01 hours with a brightness variation of 0.40±0.02 magnitude, indicative of an elongated shape (U=3−).[12]

    Diameter and albedo

    According to the surveys 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, Irenaea measures (35.703±6.145), (35.75±3.6) and (38.00±1.35) kilometers in diameter and its surface has an albedo of (0.046±0.018), (0.0502±0.012) and (0.045±0.004), respectively.[9][10][11] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous C-type asteroid of 0.057 and calculates a diameter of 30.59 kilometers based on an absolute magnitude of 11.3.[5] Alternative mean-diameter measurements published by the WISE team include (29.80±11.78 km), (32.45±7.05 km) and (37.140±11.511 km) with corresponding albedos of (0.036±0.021), (0.06±0.04) and (0.05±0.02).[5][7]

    References
    1. "794 Irenaea (A914 QB)". Minor Planet Center. Retrieved 28 March 2020.
    2. 'Irenaeus' in Noah Webster (1884) A Practical Dictionary of the English Language
    3. 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.
    4. "JPL Small-Body Database Browser: 794 Irenaea (A914 QB)" (2019-10-09 last obs.). Jet Propulsion Laboratory. Retrieved 28 March 2020.
    5. "LCDB Data for (794) Irenaea". Asteroid Lightcurve Database (LCDB). Retrieved 28 March 2020.
    6. "Asteroid 794 Irenaea – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 28 March 2020.
    7. "Asteroid 794 Irenaea". Small Bodies Data Ferret. Retrieved 28 March 2020.
    8. 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 28 March 2020.} (PDS main page)
    9. 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 28 March 2020.
    10. 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 28 March 2020.
    11. 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)
    12. Behrend, Raoul. "Asteroids and comets rotation curves – (794) Irenaea". Geneva Observatory. Retrieved 28 March 2020.
    13. 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.
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