| 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 | 90.09 yr (32,907 d) |
| Aphelion | 2.9312 AU |
| 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° | |
| Known satellites | 1 [6] (0.26Ds/Dp; P: 28.5 h) |
| 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 stony Phocaea asteroid and binary system from the inner regions of the asteroid belt, approximately 10 kilometers (6.2 miles) in diameter. It was discovered on 6 February 1967, by Swiss astronomer Paul Wild at Zimmerwald Observatory near Bern, Switzerland. [1] It was later named after Swiss astronomer Fritz Zwicky. [2] The discovery of a 2.5-kilometer sized companion was announced on 8 March 2021. [6]
Zwicky is a member of the Phocaea family ( 701 ), [4] an asteroid family with two thousand members, named after their largest member, 25 Phocaea. It orbits the Sun in the inner 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 an eccentricity of 0.25 and an inclination of 22° with respect to the ecliptic. [3] It was first identified as 1931 DL at Lowell Observatory in 1931, extending the body's observation arc by 36 years prior to its official discovery observation. [1]
This minor planet was named after Swiss astronomer Fritz Zwicky (1898–1974), who was a professor at Caltech and a pioneer in many fields, most notably in the study of galaxy clusters and supernovas, 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 term Dark matter . The lunar crater Zwicky is also named in his honour. The official naming citation was published by the Minor Planet Center on 18 April 1977 ( M.P.C. 4156). [12]
Zwicky is a bright, stony S-type asteroid, in line with the overall spectral type for members of the Phocaea family. [11] [5]
In July 2018, a rotational lightcurve of Zwicky was obtained from photometric observations by the TESS-team which gave a rotation period of (2.73364±0.00005) hours and an amplitude of (0.06±0.01) magnitude ( U=2 ). [10] Observations by Tom 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 astronomer Laurent 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 Japanese Akari satellite and NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Zwicky measures between 9.20±0.24 and 9.934±0.080 kilometers in diameter, and its surface has an albedo of 0.337 and 0.259±0.038, respectively. [7] [8] [9] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for Phocaea asteroids of 0.23, and calculates a diameter of 10.06 kilometers based on an absolute 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, that Zwicky has a satellite 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]
