_Tjilaki.png) Modelled shape of Tjilaki from itslightcurve | |
| Discovery[1] | |
|---|---|
| Discovered by | A. Massinger |
| Discovery site | Heidelberg Obs. |
| Discovery date | 15 April 1912 |
| Designations | |
| (732) Tjilaki | |
| Pronunciation | Malay:[tʃiˈlaki] |
Named after | Cilaki River[2][3] (River in Indonesia) |
| A912 HK · 1958 FC 1912 OR | |
| Orbital characteristics[4] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 106.66yr (38,959 d) |
| Aphelion | 2.5633AU |
| Perihelion | 2.3490 AU |
| 2.4561 AU | |
| Eccentricity | 0.0436 |
| 3.85 yr (1,406 d) | |
| 359.80° | |
| 0° 15m 21.96s / day | |
| Inclination | 10.994° |
| 173.35° | |
| 64.900° | |
| Physical characteristics | |
| 12.34±0.01 h[11] | |
732 Tjilaki (provisional designationA912 HK or1912 OR) is a darkbackground asteroid, approximately 36 kilometers (22 miles) in diameter, located in the inner region of theasteroid belt. It was discovered by German astronomerAdam Massinger at theHeidelberg Observatory on 15 April 1912, and later named after the Cilaki (Tjilaki inpre-reform spelling) river in Indonesia.[1][2] The darkD-type asteroid has arotation period of 12.3 hours. It was an early candidate to bevisited by theRosetta spacecraft which eventually rendezvoused comet67P/Churyumov–Gerasimenko.[11]
Tjilaki is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method to itsproper orbital elements.[5][6][7] It orbits the Sun in theinner asteroid belt at a distance of 2.3–2.6 AU once every 3 years and 10 months (1,406 days;semi-major axis of 2.46 AU). Its orbit has aneccentricity of 0.04 and aninclination of 11° with respect to theecliptic.[4] The body'sobservation arc begins atHeidelberg Observatory on 28 August 1913, or 16 months after its official discovery observation.[1]
Tjilaki was named after the Cilaki (Tjilaki) river inWest Java, Indonesia. The river rises in the mountains where the city of Malabar is located. Thenaming was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 74).[2]
In thePhase A study of theRosetta mission, Tjilaki was considered an alternativevisiting target to comet46P/Wirtanen.[11] However, both candidates were later abandoned in favor of comet67P/Churyumov–Gerasimenko, which was visited byRosetta in 2014. The retargeting was necessary as the spacecraft's launch window changed due to a delay caused by the launch failure of theHot Bird 7 satellite on the maiden flight of theAriane 5 ECA carrier rocket in 2002.
In both the Tholen- and SMASS-like taxonomic variants of theSmall Solar System Objects Spectroscopic Survey (S3OS2), Tjilaki is a darkD-type asteroid, uncommon in the inner but abundant in the outer asteroid belt as well as among theJupiter trojan population.[6][12]Polarimetric observations also determined a D-type.[13][14]
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In February 1996, a rotationallightcurve of Tjilaki was obtained fromphotometric observations over ten nights by European astronomers using theDutch 0.9-metre Telescope and theBochum 0.61-metre Telescope atLa Silla Observatory in Chile. Lightcurve analysis gave arotation period of12.34±0.01 hours with a brightness variation of0.19±0.02magnitude (U=3−).[11]
In May 2012, astronomers at thePalomar Transient Factory measured a period of12.277±0.0048 hours (U=2).[14][15] Additional observations were made by theTESS-team in January 2019, and by amateur astronomersAxel Martin and Rui Goncalves in May 2020, reporting a concurring period of (12.3286±0.0005) and (12.3216±0.00144) hours with an amplitude of (0.16±0.03) and (0.287±0.004) magnitude, respectively (U=2/n.a.).[16][17]
In 2016, a modeled lightcurve gave a concurring sidereal period of12.3411±0.0002 hours using data from the Uppsala Asteroid Photometric Catalogue, the Palomar Transient Factory survey, and individual observers, as well as sparse-in-time photometry from theNOFS, theCatalina Sky Survey, and the La Palma surveys (950). The study also determined twospin axes of (160.0°, 23.0°) and (353.0°, 24.0°) inecliptic coordinates (λ, β).[18]
According to the surveys carried out by theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer (WISE), the JapaneseAkari satellite, and the Infrared Astronomical SatelliteIRAS, Tjilaki measures (29.791±0.431), (36.49±0.43) and (37.61±1.6) kilometers in diameter and its surface has analbedo of (0.138±0.024), (0.070±0.002) and (0.0655±0.006), respectively.[8][9][10] TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.0763 and a diameter of 37.69 kilometers based on anabsolute magnitude of 10.53.[14]
Alternative mean-diameters published by the WISE team include (36.76±11.57 km) and (37.96±9.94 km) with a corresponding albedo of (0.09±0.06) and (0.15±0.05).[6][14] Twoasteroid occultations on 20 June 2005 and on 28 July 2009, gave a best-fit ellipse dimension of (33.6 km × 33.6 km) and (37.7 km × 36.4 km), respectively, each with an intermediate quality rating of 2.[6] These timed observations are taken when the asteroid passes in front of a distant star.[6]
