| Discovery[1] | |
|---|---|
| Discovered by | K. Reinmuth |
| Discovery site | Heidelberg Obs. |
| Discovery date | 31 October 1923 |
| Designations | |
| (1009) Sirene | |
| Pronunciation | German:[ˈziːʁeːnə] |
Named after | Siren (Σειρήν - Sīrēn)(Greek mythology)[2] |
| 1923 PE | |
| Mars-crosser[1][3] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 92.69 yr (33,854 days) |
| Aphelion | 3.8207AU |
| Perihelion | 1.4259 AU |
| 2.6233 AU | |
| Eccentricity | 0.4564 |
| 4.25yr (1,552 days) | |
| 11.512° | |
| 0° 13m 55.2s / day | |
| Inclination | 15.775° |
| 229.46° | |
| 186.35° | |
| Earth MOID | 0.4384 AU · 170.8LD |
| Physical characteristics | |
| Dimensions | 5 km(est. at0.20)[4] |
| 13.9[1] | |
Sirene (minor planet designation:1009 Sirene), provisional designation1923 PE, is an eccentricasteroid and sizableMars-crosser from the central regions of theasteroid belt, approximately 5 kilometers in diameter. It was discovered by German astronomerKarl Reinmuth at theHeidelberg-Königstuhl State Observatory on 31 October 1923.[3] The asteroid was named after theSiren from Greek mythology.[2]
Sirene is aMars-crossing asteroid with a notably largesemi-major axis is 2.62 AU, due to its higheccentricity of 0.46.[1] It orbits the Sun in thecentral main-belt at a distance of 1.4–3.8 AU once every 4 years and 3 months (1,552 days). Its orbit has aninclination of 16° with respect to theecliptic.[1]
The body'sobservation arc begins 9 days after its official discovery observation atBergedorf Observatory in Hamburg.[3] On 8 June 1949,Sirene passed 0.049 AU (7,300,000 km; 4,600,000 mi) from Mars.
Sirene had been of great interest in 1930s.[5] After its discovery, it was observed atAlgiers, Bergedorf, Heidelberg,Milan,Vienna andWilliams Bay in the United States, where it became too faint to be accurately observed. It was regarded as an excellent example of a member of the then called "Aethra group" –132 Aethra was the first discovered Mars-crossing asteroid – highly appropriate to measure the exact mass of Mars on its nextopposition nearperihelion in 1937.[5] However, after its last observation at Williams Bay in 1924,Sirene had only been observed once atTurku Observatory in 1940, and remained unobserved until the 1980s.[3]
As of 2017, no rotationallightcurve ofSirene has been obtained from photometric observations. The asteroid'srotation period, shape and poles remain unknown.[1][6]
Sirene has not been observed by any large-scale, space-based surveys such asIRAS,NEOWISE andAkari.[1][6] Based on a generic magnitude-to-diameter conversion,Sirene measures 5 kilometers in diameter for anabsolute magnitude of 13.9 and an assumed stonyalbedo of 0.20.[4] For an assumed albedo of 0.10 and 0.05, its calculated diameter would increase to 7.1 and 10 kilometers, respectively.[4]
Thisminor planet was named fromGreek mythology after theSiren, who lured nearby sailors with their enchanting music and voices to shipwreck on the rocky coast of their island. The official naming citation was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 96).[2]
