| Discovery[1] | |
|---|---|
| Discovered by | J. Palisa |
| Discovery site | Vienna Obs. |
| Discovery date | 27 August 1914 |
| Designations | |
| (794) Irenaea | |
| Pronunciation | /ɪrɪˈniːə/[2] |
Named after | Irene Hillebrand, daughter ofEdmund 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 arc | 83.12yr (30,360 d) |
| Aphelion | 4.0559AU |
| Perihelion | 2.2004 AU |
| 3.1281 AU | |
| Eccentricity | 0.2966 |
| 5.53 yr (2,021 d) | |
| 31.160° | |
| 0° 10m 41.16s / day | |
| Inclination | 5.4193° |
| 160.40° | |
| 131.27° | |
| Physical characteristics | |
| 9.14±0.01 h[12] | |
| C(assumed)[5] | |
794 Irenaea (prov. designation:A914 QBor1914 VB) is a darkbackground asteroid from the outer regions of theasteroid belt. It was discovered on 27 August 1914, by Austrian astronomerJohann Palisa at theVienna Observatory.[1] The presumedC-type asteroid has arotation period of 9.1 hours and measures approximately 36 kilometers (22 miles) in diameter. It was likely named after Irene Hillebrand, daughter of Austrian astronomerEdmund Weiss (1837–1917).[3]
Irenaea is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method to itsproper orbital elements.[6][7][8] It orbits the Sun in theouter 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 aneccentricity of 0.30 and aninclination of 5° with respect to theecliptic.[4] The body'sobservation arc begins atBergedorf Observatory in Hamburg on 9 December 1915, more than a year after its official discovery observation atVienna Observatory on 27 August 1914.[1]
According to Alexander Schnell, thisminor planet was likely named after Irene Hillebrand, née Weiss, daughter of Austrian astronomerEdmund Weiss (1837–1917), director of theVienna Observatory, and wife to astronomerKarl Hillebrand [de] (1861–1939). The name received anaea-suffix as "Irene" was already given to asteroid14 Irene.[3] Palisa also named asteroid722 Frieda after her daughter, Frieda Hillebrand.[13]
Irenaea is an assumed, carbonaceousC-type asteroid.[5] The asteroid's low albedo around 0.05(see below) agrees with this assumption.
In May 2008, a rotationallightcurve ofIrenaea was obtained fromphotometric observations by Italian amateur astronomerSilvano Casulli. Lightcurve analysis gave arotation period of9.14±0.01 hours with a brightness variation of0.40±0.02magnitude, indicative of an elongated shape (U=3−).[12]
According to the surveys carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer (WISE), the Infrared Astronomical SatelliteIRAS, and the JapaneseAkari satellite,Irenaea measures (35.703±6.145), (35.75±3.6) and (38.00±1.35) kilometers in diameter and its surface has analbedo of (0.046±0.018), (0.0502±0.012) and (0.045±0.004), respectively.[9][10][11] TheCollaborative 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 anabsolute magnitude of 11.3.[5] Alternativemean 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]
