_Pickeringia.png) Shape ofPickeringia from modeledlightcurve | |
| Discovery[1] | |
|---|---|
| Discovered by | J. H. Metcalf |
| Discovery site | Winchester Obs. (799) |
| Discovery date | 20 March 1914 |
| Designations | |
| (784) Pickeringia | |
Named after |
|
| A914 FC · 1914 UM | |
| Orbital characteristics[3] | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 105.82yr (38,652 d) |
| Aphelion | 3.8458AU |
| Perihelion | 2.3455 AU |
| 3.0956 AU | |
| Eccentricity | 0.2423 |
| 5.45 yr (1,989 d) | |
| 97.354° | |
| 0° 10m 51.6s / day | |
| Inclination | 12.284° |
| 14.917° | |
| 238.01° | |
| Physical characteristics | |
| Mass | (3.74±0.32)×1018 kg[10] |
Meandensity | 12.70±3.49 g/cm3[10] |
| 13.144±0.005 h[11] | |
784 Pickeringia (prov. designation:A914 FCor1914 UM) is a largebackground asteroid, approximately 76 kilometers (47 miles) in diameter, located in the outer region of theasteroid belt. It was discovered on 20 March 1914, by American astronomerJoel Hastings Metcalf at the Winchester Observatory (799) in Massachusetts.[1] The darkC-type asteroid has arotation period of 13.1 hours and an irregular shape. It was named after American astronomersEdward Charles Pickering (1846–1919) and his brotherWilliam Henry Pickering (1858–1938).[2]
Pickeringia is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method to itsproper orbital elements.[4][5][6] It orbits the Sun in theouter asteroid belt at a distance of 2.3–3.8 AU once every 5 years and 5 months (1,989 days;semi-major axis of 3.1 AU). Its orbit has aneccentricity of 0.24 and aninclination of 12° with respect to theecliptic.[3] The body'sobservation arc begins atHeidelberg Observatory on 30 September 1921, more than seven years after its official discovery observation at Winchester Observatory (799).[1]
Thisminor planet was named after American astronomersEdward Charles Pickering (1846–1919) and his brotherWilliam Henry Pickering (1858–1938), who were the directors of theHarvard Observatory and theBoyden Station at Arequipa, respectively. William Henry also discoveredPhoebe, an irregularmoon of Saturn. Thenaming was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 78).[2] The lunar craterPickering and the Martian craterPickering were also named in honor of the two astronomers.[13][14]
In the Bus–BinzelSMASS classification,Pickeringia is a common, carbonaceousC-type asteroid.[3]
In January 2017, a rotationallightcurve ofPickeringia was obtained fromphotometric observations by the Spanish group of asteroids observers (OBAS). Lightcurve analysis gave arotation period of13.144±0.005 hours with a brightness variation of0.17±0.03magnitude (U=2+).[11]
The result supersedes observations taken during the 1990s by European astronomers using theESO 0.5-metre telescope atLa Silla Observatory, Chile, which gave a period of13 hours with an amplitude of0.40 magnitude (U=2).[15] as well as a period determination by French amateur astronomerLaurent Bernasconi in December 2004, which gave13.17±0.05 h and an amplitude of0.20±0.01 magnitude (U=2).[16]
Two modeled lightcurves, published byJosef Ďurech andJosef Hanuš in 2016, using photometric data from the Lowell Photometric Database (LPD) and other sources, gave a sidereal period of13.16995±0.00001 and13.16998±0.00005, respectively. Each modeled lightcurve also determined twospin axes of (99.0°, 67.0°) and (283.0°, 30.0°), as well as (282.0°, 35.0°) and (103.0°, 68.0°) inecliptic coordinates (λ, β), respectively.[17][18] The online version of theDatabase of Asteroid Models from Inversion Techniques gives two poles at (103°, 68.0°) and (282°, 35.0°) with a nearly identical sidereal period.[a]
According to the surveys carried out by the JapaneseAkari satellite, theNEOWISE mission of NASA'sWide-field Infrared Survey Explorer (WISE), and the Infrared Astronomical SatelliteIRAS,Pickeringia measures (74.89±0.92), (75.596±0.311) and (89.42±3.4) kilometers in diameter and its surface has analbedo of (0.080±0.002), (0.086±0.014) and (0.0555±0.005), respectively.[7][8][9] TheCollaborative Asteroid Lightcurve Link derives an albedo of 0.0423 and a diameter of 89.19 kilometers based on anabsolute magnitude of 9.3.[19] while Carry gives a diameter of82.52±7.18 km and estimates a mass of(3.74±0.32)×1018 kilogram from an unrealistic density of12.70±3.49 g/cm3.[10] Alternative mean-diameter measurements published by the WISE team include (70.14±18.05 km), (89.13±13.47 km) and (89.673±1.178 km) with corresponding albedos of (0.049±0.348), (0.0552±0.0109) and (0.06±0.02).[5][19] On 7 August 2008, anasteroid occultation ofPickeringia gave a best-fit ellipse dimension of (89.0 km × 89.0 km), with a poor quality rating of 1. These timed observations are taken when the asteroid passes in front of a distant star.[5]
