| Discovery[1] | |
|---|---|
| Discovered by | A. Schwassmann |
| Discovery site | Bergedorf Obs. |
| Discovery date | 18 November 1922 |
| Designations | |
| (989) Schwassmannia | |
| Pronunciation | /ʃwæsˈmæniə,ʃvɑːs-/ |
Named after | Friedrich Karl Arnold Schwassmann (discoverer himself)[2] |
| A922 WD · 1922 MW 1935 UE · 1935 UF | |
| main-belt[1][3] · (middle) background[4] | |
| Orbital characteristics[3] | |
| Epoch 27 April 2019 (JD 2458600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 96.49yr (35,244 d) |
| Aphelion | 3.3261AU |
| Perihelion | 1.9915 AU |
| 2.6588 AU | |
| Eccentricity | 0.2510 |
| 4.34 yr (1,584 d) | |
| 83.840° | |
| 0° 13m 38.28s / day | |
| Inclination | 14.700° |
| 243.40° | |
| 165.73° | |
| Physical characteristics | |
| 107.85±0.01 h[8][9] | |
| 11.8[1][3] | |
989 Schwassmannia (prov. designation:A922 WDor1922 MW) is a stonybackground asteroid and aslow rotator from the central regions of theasteroid belt, approximately 12.5 kilometers (7.8 miles) in diameter. It was discovered on 18 November 1922, by astronomerFriedrich Karl Arnold Schwassmann at theBergedorf Observatory in Hamburg, Germany.[1] The brightS/T-type asteroid has a longrotation period of 107.9 hours.[4] It was named after the discoverer himself.[2]
Schwassmannia is a non-family asteroid of the main belt'sbackground population when applying thehierarchical clustering method to itsproper orbital elements.[11] It orbits the Sun in thecentral main-belt at a distance of 2.0–3.3 AU once every 4 years and 4 months (1,584 days;semi-major axis of 2.66 AU). Its orbit has aneccentricity of 0.25 and aninclination of 15° with respect to theecliptic.[3] The body'sobservation arc begins at theHeidelberg Observatory on 12 November 1922, just 6 days prior to its official discovery observation at theBergedorf Observatory in Hamburg.[1]
Thisminor planet was named after its discoverer, German astronomer Arnold Schwassmann (1870–1964), who discoveredfour comets and 22 asteroids in total (including this one). Schwassmann worked at thePotsdam (Berlin) and Hamburg–Bergedorf observatories. The officialnaming citation was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 94).[2]
In the Tholen- and SMASS-like taxonomy of theSmall Solar System Objects Spectroscopic Survey (S3OS2),Schwassmannia is anS-type andT-type asteroid, respectively.[4][10]
In November 2013, a rotationallightcurve ofSchwassmannia was obtained fromphotometric observations by astronomers Vladimir Benishek at Sopot Astronomical Observatory (K90), Serbia, AmericanFrederick Pilcher at his Organ Mesa Observatory (G50), New Mexico, and Luis Martinez at Lenomiya Observatory (H13) at Casa Grande in Arizona. Lightcurve analysis gave a well-definedrotation period of107.85±0.01 hours with a brightness amplitude of0.35±0.02magnitude (U=3).[8][9] Alternative observations with a lower rated quality byRobert Stephens at the Center for Solar System Studies (U81) in September 2013 gave a period of120.3±1 hours (U=2).[12][a] The results supersede an earlier, tentative observation by Italian Federico Manzini at the Sozzago Astronomical Station (A12) from October 2004, with an incorrect period 4.5 hours (U=1).[4][13]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite and theNEOWISE mission of NASA's WISE telescope,Schwassmannia measures between12.20±1.12 and12.86±0.8 kilometers in diameter and its surface has a highalbedo between 0.20 and 0.31.[5][6][7] TheCollaborative Asteroid Lightcurve Link adopts the result from IRAS, that is, an albedo of 0.2037 and a diameter of 12.86 kilometers based on anabsolute magnitude of 11.8.[8]
