_Sigrid.png) Shape ofSigrid modelled from itslightcurve | |
| Discovery[1] | |
|---|---|
| Discovered by | E. Delporte |
| Discovery site | Uccle Obs. |
| Discovery date | 26 August 1938 |
| Designations | |
| (1493) Sigrid | |
Named after | Sigrid Strömgren[2] (wife of astronomer) Bengt Strömgren |
| 1938 QB · 1934 NB1 1934 PW · 1957 UT 1961 TM1 · 1961 XL 1977 UN · A908 WA A916 YD | |
| main-belt · (inner) Nysa[3][4] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 108.52 yr (39,636 days) |
| Aphelion | 2.9175AU |
| Perihelion | 1.9416 AU |
| 2.4295 AU | |
| Eccentricity | 0.2009 |
| 3.79yr (1,383 days) | |
| 318.09° | |
| 0° 15m 37.08s / day | |
| Inclination | 2.5772° |
| 330.58° | |
| 1.6890° | |
| Physical characteristics | |
| Dimensions | 22.111±0.200 km[5] 22.93±6.77 km[6] 23±2 km[7] 23.76±3.46 km[8] 24.03±2.1 km[3][9] 24.92±8.61 km[10] 25.10±0.42 km[11] 27.8±5.6 km[12] 28.905±0.401 km[13] |
| 22.68±0.02 h[14] 43.179±0.005 h[15] 43.1795±0.0001 h[16] 43.296±0.048h[17] | |
| 0.034±0.007[13] 0.036±0.067[10] 0.0398±0.0028[5] 0.04±0.02[6][12] 0.04±0.03[8] 0.048±0.002[11] 0.0489±0.010[9] 0.05±0.01[7] | |
| Tholen =F[1][3] SMASS = Xc[1] · P[5] B–V = 0.643[1] U–B = 0.225[1] | |
| 11.99[1][3][5][6][7][9][11][12] · 12.24[8][10] · 12.35±0.23[18] | |
1493 Sigrid, provisional designation1938 QB, is a dark Nysianasteroid from the inner regions of theasteroid belt, approximately 24 kilometers in diameter. It was discovered on 26 August 1938, by Belgian astronomerEugène Delporte at theRoyal Observatory of Belgium in Uccle.[19] It was named after Sigrid Strömgren, wife of astronomerBengt Strömgren.[2]
Sigrid is a member of theNysa family (405),[4] the largestasteroid family of the main belt, consisting of stony and carbonaceous subfamilies. The family, named after44 Nysa, is located in the inner belt near theKirkwood gap (3:1 orbital resonance with Jupiter), a depleted zone that separates the central main belt.[20]: 23
It orbits the Sun in theinner main-belt at a distance of 1.9–2.9 AU once every 3 years and 9 months (1,383 days). Its orbit has aneccentricity of 0.20 and aninclination of 3° with respect to theecliptic.[1] The asteroid was first identified asA908 WA atHeidelberg Observatory in November 1908. The body'sobservation arc begins with its official discovery observation at Uccle in August 1938.[19]
In theTholen classification,Sigrid is anF-type asteroid (which agrees with the overallspectral type of the Polanian subgroup).[1][3] In theSMASS classification, it is a Xc-subtype, which transitions between theX- andC-type asteroids.[1] It has also been characterized as a primitiveP-type asteroid by theWide-field Infrared Survey Explorer (WISE).[5]
In August 2006, a rotationallightcurve ofSigrid was obtained from photometric observations at the Mount Tarana and Cecil Observatory in NSW, Australia. Lightcurve analysis gave arotation period of 43.296 hours with a brightness variation of 0.6magnitude (U=2).[17] In October 2010, Raymond Poncy found a period of 22.68 hours (or half the previous period solution) and an amplitude of 0.38 magnitude (U=2-).[14] While not being aslow rotator, the body's period is significantly longer than the typical 2 to 20 hours seen among the majority of asteroids.
The asteroids lightcurve has also been modeled, using photometric data from the Lowell Photometric Database (LPD) and other sources. Modelling gave a concurring period of 43.179 and 43.1795 hours,[15][16] as well as two spin axis of (183.0°, 69°) and (350.0°, 69°) inecliptic coordinates (λ, β).[16]
According to the surveys carried out by the Infrared Astronomical SatelliteIRAS, the JapaneseAkari satellite and theNEOWISE mission of NASA's WISE telescope,Sigrid measures between 22.111 and 28.905 kilometers in diameter and its surface has a lowalbedo between 0.034 and 0.05.[5][6][7][8][9][10][11][12][13]
TheCollaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is an albedo of 0.0489 and a diameter of 24.03 kilometers based on anabsolute magnitude of 11.99.[3]
Thisminor planet was named after Sigrid Strömgren, wife of the Danish-American astronomerBengt Strömgren, after whom the asteroid1846 Bengt was named. The official naming citation was mentioned inThe Names of the Minor Planets byPaul Herget in 1955 (H 134;RI 2297).[2]
