| Discovery[1] | |
|---|---|
| Discovered by | P. Wild |
| Discovery site | Zimmerwald Obs. |
| Discovery date | 6 February 1967 |
| Designations | |
| (1803) Zwicky | |
Named after | Fritz Zwicky[2] (Swiss astronomer) |
| 1967 CA · 1931 DL | |
| main-belt[1][3] · (inner) Phocaea[4][5] | |
| Orbital characteristics[3] | |
| Epoch 17 December 2020 (JD 2459200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 90.09yr (32,907 d) |
| Aphelion | 2.9312AU |
| Perihelion | 1.7685 AU |
| 2.3498 AU | |
| Eccentricity | 0.2474 |
| 3.60 yr (1,316 d) | |
| 284.97° | |
| 0° 16m 24.96s / day | |
| Inclination | 21.553° |
| 337.24° | |
| 253.96° | |
| Knownsatellites | 1[6](0.26Ds/Dp;P: 28.5h) |
| Physical characteristics | |
| 2.73364±0.00005 h[10] | |
| S[11][5] | |
| 12.23[1] 12.24[3] | |
1803 Zwicky,prov. designation:1967 CA, is a stonyPhocaea asteroid andbinary system from the inner regions of theasteroid belt, approximately 10 kilometers (6.2 miles) in diameter. It was discovered on 6 February 1967, by Swiss astronomerPaul Wild atZimmerwald Observatory near Bern, Switzerland.[1] It was later named after Swiss astronomerFritz Zwicky.[2] The discovery of a 2.5-kilometer sizedcompanion was announced on 8 March 2021.[6]
Zwicky is a member of thePhocaea family (701),[4] anasteroid family with two thousand members, named after their largest member,25 Phocaea. It orbits the Sun in theinner main-belt at a distance of 1.8–2.9 AU once every 3 years and 7 months (1,316 days;semi-major axis of 2.35 AU). Its orbit has aneccentricity of 0.25 and aninclination of 22° with respect to theecliptic.[3] It was first identified as1931 DL atLowell Observatory in 1931, extending the body'sobservation arc by 36 years prior to its official discovery observation.[1]
Thisminor planet was named after Swiss astronomerFritz Zwicky (1898–1974), who was a professor atCaltech and a pioneer in many fields, most notably in the study ofgalaxy clusters andsupernovas, in high-energy astrophysics, and in developing jet propulsion for spacecraft and airplanes.[2] He was the first to infer the existence of unseen matter and coined the termDark matter. The lunar craterZwicky is also named in his honour. The officialnaming citation was published by theMinor Planet Center on 18 April 1977 (M.P.C. 4156).[12]
Zwicky is a bright, stonyS-type asteroid, in line with the overall spectral type for members of thePhocaea family.[11][5]
In July 2018, a rotationallightcurve ofZwicky was obtained fromphotometric observations by theTESS-team which gave arotation period of (2.73364±0.00005) hours and an amplitude of (0.06±0.01)magnitude (U=2).[10] Observations byTom Polakis, who also discovered a satellite(see below) determined a very similar period of (2.7329±0.0002) hours with a brightness variation of (0.105±0.035) (U=2).[6] These more recent result are replacing a previous observation from March 2003, of a fragmentary lightcurve by French amateur astronomerLaurent Bernasconi that gave a tentative period of 27.1 hours and an amplitude of 0.08 (U=1).[13]
According to the surveys carried out by the JapaneseAkari satellite and NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission,Zwicky measures between9.20±0.24 and9.934±0.080 kilometers in diameter, and its surface has analbedo of0.337 and0.259±0.038, respectively.[7][8][9] TheCollaborative Asteroid Lightcurve Link assumes a standard albedo for Phocaea asteroids of 0.23, and calculates a diameter of 10.06 kilometers based on anabsolute magnitude of 12.2.[5] The WISE team also published an alternative mean-diameters of (8.03±1.37) and (10.229±0.082) kilometers with a corresponding albedo of (0.35) and (0.2466).[4][14][15]
Photometric observations at the Command Module Observatory (V02) by Tom Polakis on 21 February 2021 revealed, thatZwicky has asatellite in its orbit. The moon has a diameter of approximately 2.50 kilometers, or 26% of that of its primary, and an orbital period of 28.46 hours.[6]
