1493 Sigrid

1493 Sigrid, provisional designation 1938 QB, is a dark Nysian asteroid from the inner regions of the asteroid belt, approximately 24 kilometers in diameter. It was discovered on 26 August 1938, by Belgian astronomer Eugène Delporte at the Royal Observatory of Belgium in Uccle.[19] It was named after Sigrid Strömgren, wife of astronomer Bengt Strömgren.[2]

1493 Sigrid
001493-asteroid shape model (1493) Sigrid.png
Shape of Sigrid modelled from its lightcurve
Discovery [1]
Discovered byE. Delporte
Discovery siteUccle Obs.
Discovery date26 August 1938
(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)
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc108.52 yr (39,636 days)
Aphelion2.9175 AU
Perihelion1.9416 AU
2.4295 AU
3.79 yr (1,383 days)
0° 15m 37.08s / day
Physical characteristics
Dimensions22.111±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±0.048 h[17]
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]

Orbit and classificationEdit

Sigrid is a member of the Nysa family (405),[4] the largest asteroid family of the main belt, consisting of stony and carbonaceous subfamilies. The family, named after 44 Nysa, is located in the inner belt near the Kirkwood gap (3:1 orbital resonance with Jupiter), a depleted zone that separates the central main belt.[20]:23

It orbits the Sun in the inner main-belt at a distance of 1.9–2.9 AU once every 3 years and 9 months (1,383 days). Its orbit has an eccentricity of 0.20 and an inclination of 3° with respect to the ecliptic.[1] The asteroid was first identified as A908 WA at Heidelberg Observatory in November 1908. The body's observation arc begins with its official discovery observation at Uccle in August 1938.[19]

Physical characteristicsEdit

Spectral typeEdit

In the Tholen classification, Sigrid is an F-type asteroid (which agrees with the overall spectral type of the Polanian subgroup).[1][3] In the SMASS classification, it is a Xc-subtype, which transitions between the X- and C-type asteroids.[1] It has also been characterized as a primitive P-type asteroid by the Wide-field Infrared Survey Explorer (WISE).[5]


Rotation period an amplitudeEdit

In August 2006, a rotational lightcurve of Sigrid was obtained from photometric observations at the Mount Tarana and Cecil Observatory in NSW, Australia. Lightcurve analysis gave a rotation period of 43.296 hours with a brightness variation of 0.6 magnitude (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 a slow rotator, the body's period is significantly longer than the typical 2 to 20 hours seen among the majority of asteroids.

Spin axisEdit

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°) in ecliptic coordinates (λ, β).[16]

Diameter and albedoEdit

According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's WISE telescope, Sigrid measures between 22.111 and 28.905 kilometers in diameter and its surface has a low albedo between 0.034 and 0.05.[5][6][7][8][9][10][11][12][13]

The Collaborative 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 an absolute magnitude of 11.99.[3]


This minor planet was named after Sigrid Strömgren, wife of the Danish-American astronomer Bengt Strömgren, after whom the asteroid 1846 Bengt was named. The official naming citation was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 134; RI 2297).[2]


  1. ^ a b c d e f g h i j "JPL Small-Body Database Browser: 1493 Sigrid (1938 QB)" (2017-06-05 last obs.). Jet Propulsion Laboratory. Retrieved 19 October 2017.
  2. ^ a b c Schmadel, Lutz D. (2007). "(1493) Sigrid". Dictionary of Minor Planet Names – (1493) Sigrid. Springer Berlin Heidelberg. p. 119. doi:10.1007/978-3-540-29925-7_1494. ISBN 978-3-540-00238-3.
  3. ^ a b c d e f "LCDB Data for (1493) Sigrid". Asteroid Lightcurve Database (LCDB). Retrieved 19 October 2017.
  4. ^ a b "Asteroid 1493 Sigrid – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 26 October 2019.
  5. ^ a b c d e f Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90.
  6. ^ a b c d Nugent, C. R.; Mainzer, A.; Masiero, J.; Bauer, J.; Cutri, R. M.; Grav, T.; et al. (December 2015). "NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos". The Astrophysical Journal. 814 (2): 13. arXiv:1509.02522. Bibcode:2015ApJ...814..117N. doi:10.1088/0004-637X/814/2/117. Retrieved 19 October 2017.
  7. ^ a b c d Alí-Lagoa, V.; de León, J.; Licandro, J.; Delbó, M.; Campins, H.; Pinilla-Alonso, N.; et al. (June 2013). "Physical properties of B-type asteroids from WISE data". Astronomy and Astrophysics. 554: 16. arXiv:1303.5487. Bibcode:2013A&A...554A..71A. doi:10.1051/0004-6361/201220680. Retrieved 19 October 2017.
  8. ^ a b c d Nugent, C. R.; Mainzer, A.; Bauer, J.; Cutri, R. M.; Kramer, E. A.; Grav, T.; et al. (September 2016). "NEOWISE Reactivation Mission Year Two: Asteroid Diameters and Albedos". The Astronomical Journal. 152 (3): 12. arXiv:1606.08923. Bibcode:2016AJ....152...63N. doi:10.3847/0004-6256/152/3/63. Retrieved 19 October 2017.
  9. ^ a b c d Tedesco, E. F.; Noah, P. V.; Noah, M.; Price, S. D. (October 2004). "IRAS Minor Planet Survey V6.0". NASA Planetary Data System. 12: IRAS-A-FPA-3-RDR-IMPS-V6.0. Bibcode:2004PDSS...12.....T. Retrieved 22 October 2019.
  10. ^ a b c d Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 19 October 2017.
  11. ^ a b c d Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. Retrieved 17 October 2019. (online, AcuA catalog p. 153)
  12. ^ a b c d Alí-Lagoa, V.; Licandro, J.; Gil-Hutton, R.; Cañ; ada-Assandri, M.; Delbo', M.; et al. (June 2016). "Differences between the Pallas collisional family and similarly sized B-type asteroids" (PDF). Astronomy and Astrophysics. 591: 11. Bibcode:2016A&A...591A..14A. doi:10.1051/0004-6361/201527660. Retrieved 19 October 2017.
  13. ^ a b c Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; et al. (August 2014). "Main-belt Asteroids with WISE/NEOWISE: Near-infrared Albedos". The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 19 October 2017.
  14. ^ a b Behrend, Raoul. "Asteroids and comets rotation curves – (1493) Sigrid". Geneva Observatory. Retrieved 19 October 2017.
  15. ^ a b Hanus, J.; Broz, M.; Durech, J.; Warner, B. D.; Brinsfield, J.; Durkee, R.; et al. (November 2013). "An anisotropic distribution of spin vectors in asteroid families". Astronomy and Astrophysics. 559: 19. arXiv:1309.4296. Bibcode:2013A&A...559A.134H. doi:10.1051/0004-6361/201321993. Retrieved 19 October 2017.
  16. ^ a b c Durech, J.; Hanus, J.; Oszkiewicz, D.; Vanco, R. (March 2016). "Asteroid models from the Lowell photometric database". Astronomy and Astrophysics. 587: 6. arXiv:1601.02909. Bibcode:2016A&A...587A..48D. doi:10.1051/0004-6361/201527573. Retrieved 19 October 2017.
  17. ^ a b Bembrick, Colin; Byron, Jeff (March 2007). "A Rotation Period for 1493 Sigrid". The Minor Planet Bulletin. 34 (1): 1. Bibcode:2007MPBu...34....1B. ISSN 1052-8091. Retrieved 19 October 2017.
  18. ^ Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 19 October 2017.
  19. ^ a b "1493 Sigrid (1938 QB)". Minor Planet Center. Retrieved 19 October 2017.
  20. ^ Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). Identification and Dynamical Properties of Asteroid Families. Asteroids IV. pp. 297–321. arXiv:1502.01628. Bibcode:2015aste.book..297N. doi:10.2458/azu_uapress_9780816532131-ch016. ISBN 9780816532131.

External linksEdit