| Discovery[1] | |
|---|---|
| Discovered by | A. Kopff |
| Discovery site | Heidelberg Obs. |
| Discovery date | 8 August 1909 |
| Designations | |
| (684) Hildburg | |
Named after | unknown[2] |
| A909 PB · 1928 PB 1938 CT · 1909 HD | |
| main-belt[1][3] · (inner)[4] background[5][6][7] | |
| Orbital characteristics[3] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 110.43yr (40,335 d) |
| Aphelion | 2.5172AU |
| Perihelion | 2.3461 AU |
| 2.4317 AU | |
| Eccentricity | 0.0352 |
| 3.79 yr (1,385 d) | |
| 122.80° | |
| 0° 15m 35.64s / day | |
| Inclination | 5.5224° |
| 336.36° | |
| 290.44° | |
| Physical characteristics | |
| 15.89±0.01 h[11] | |
684 Hildburg (prov. designation:A909 PBor1909 HD) is a stonybackground asteroid from the inner regions of theasteroid belt. It was discovered on 8 August 1909, by German astronomerAugust Kopff at theHeidelberg-Königstuhl State Observatory in southwest Germany.[1] TheS-type asteroid has arotation period of 15.9 hours and measures approximately 19 kilometers (12 miles) in diameter. Any reference to the origin of the asteroid's name is unknown.[2]
Hildburg 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 main-belt at a distance of 2.3–2.5 AU once every 3 years and 9 months (1,385 days;semi-major axis of 2.43 AU). Its orbit has aneccentricity of 0.04 and aninclination of 6° with respect to theecliptic.[3] The body'sobservation arc begins atHeidelberg Observatory on 19 August 1909, just eleven nights after its official discovery observation.[1]
Thisminor planet's name may have been inspired by the two letters of its provisional designation, "1909 HD". However, any reference to a person or occurrence is unknown.[2] It is speculated that the name comes from a list created in 1913 by theAstronomisches Rechen-Institut (ARI) containing suggestions of female names from history and mythology for the naming of minor planets (AN 196, 137). At the time, the naming process was not well developed and the ARI feared inconsistencies and potential confusion. The list was sent to several German astronomers, including Kopff, with the invitation to name all of their made discoveries up to number 700.[13] It is therefore unlikely that this asteroid's name refers to a known person such as Austrian actressStephanie Hildburg [de] (1862–1942).
Among the many thousands ofnamed minor planets,Hildburg is one of 120 asteroids for whichno naming citation has been published. All of these asteroids with an unknown meaning have low numbers, beginning with164 Eva and ending with1514 Ricouxa, all discovered between 1876 and the 1930s, predominantly by astronomersAuguste Charlois,Johann Palisa,Max Wolf andKarl Reinmuth.[14]
Hildburg is a common stonyS-type asteroid according to observations byRichard Binzel conducted atMcDonald andCerro Tololo observatories in May 1984.[4][12]
In March 2014, a rotationallightcurve ofHildburg was obtained fromphotometric observations by Italian astronomer Andrea Ferrero at the Bigmuskie Observatory (B88) in Mombercelli, Italy. Lightcurve analysis gave arotation period of15.89±0.01 hours with a brightness variation of0.22±0.02magnitude (U=2). However, the result is ambiguous and allows for an alternative period solution of 11.92 hours.[11] In April 2008, French amateur astronomerRené Roy determined a period of14.2±1.0 hours with a low amplitude of0.07±0.02 magnitude (U=2−).[15] In May 1984, the object's first measurement by Richard Binzel gave a period of11.92 h and an amplitude of 0.23 magnitude (U=2).[12]
According to the surveys carried out by the JapaneseAkari satellite and theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer (WISE),Hildburg measures (16.28±0.34) and (19.040±0.188) kilometers in diameter and its surface has analbedo of (0.186±0.009) and (0.238±0.043), respectively.[8][9][10]
TheCollaborative Asteroid Lightcurve Link assumes a standard albedo for astony asteroid of 0.20 and derives a diameter of 19.28 kilometers based on anabsolute magnitude of 10.94.[4] The WISE team also published an alternative mean-diameter (22.386±0.080 km) and an albedo of (0.1485±0.0159).[4] On 23 August 2004, anasteroid occultation gave a best-fit ellipse dimension of (17.0 km × 17.0 km) with a low quality rating of 1.[6] These timed observations are taken when the asteroid passes in front of a distant star.[6]
