960 Birgit (prov. designation: A921 TG or 1921 KH) is a background asteroid, approximately 8 kilometers (5 miles) in diameter, located in the Florian region of the inner asteroid belt. It was discovered on 1 October 1921, by astronomer Karl Reinmuth at the Heidelberg Observatory in southern Germany. The possibly S-type asteroid has a rotation period of 8.9 hours. It was named after Birgit Asplind, daughter of Swedish astronomer Bror Asplind (1890–1954).
|Discovered by||K. Reinmuth|
|Discovery site||Heidelberg Obs.|
|Discovery date||1 October 1921|
|MPC designation||(960) Birgit|
(daughter of Bror Asplind)
|A921 TG · 1921 KH|
|main-belt  · (inner)|
background  (Florian)
|Orbital characteristics |
|Epoch 31 May 2020 (JD 2459000.5)|
|Uncertainty parameter 0|
|Observation arc||98.26 yr (35,889 d)|
|3.37 yr (1,232 d)|
|0° 17m 32.28s / day|
Orbit and classificationEdit
Located in the Florian region, Birgit is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the inner asteroid belt at a distance of 1.9–2.6 AU once every 3 years and 4 months (1,232 days; semi-major axis of 2.25 AU). Its orbit has an eccentricity of 0.17 and an inclination of 3° with respect to the ecliptic. The body's observation arc begins at Heidelberg on 25 October 1925, three weeks after its official discovery observation.
This minor planet was named after Birgit Asplind, daughter of Swedish astronomer Bror Ansgar Asplind (1890–1954). Asteroids 958 Asplinda, 959 Arne and 961 Gunnie are named after him and his other two children, respectively. The naming was mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 92).
Based on its determined albedo, Birgit is an assumed S-type asteroid. The albedo determined by the Wide-field Infrared Survey Explorer (WISE) for this asteroid agrees with that assumption (see below).
In February 2007, a rotational lightcurve of Birgit was obtained from photometric observations by Agnieszka Kryszczyńska at Poznań Observatory, Poland, and international collaborators. Lightcurve analysis gave a rotation period of 8.85±0.05 hours with a brightness variation of 0.28±0.02 magnitude (U=2+).[a] The result supersedes observations by Federico Manzini, Roberto Crippa, and Pierre Antonini from August 2005, who determined a poorly rated period of 17.3558±0.0005 hours with an amplitude of 0.25±0.01 magnitude (U=1+).
Diameter and albedoEdit
According to the survey carried out by the NEOWISE mission of NASA's WISE telescope, Birgit measures 7.506±0.110 kilometers in diameter and its surface has an albedo of 0.217±0.027. Another published measurement by the WISE team gives a mean-diameter of 8.154±0.566 km with an albedo of 0.291±0.044. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for a stony asteroid of 0.20 and calculates a diameter of 9.40 kilometers based on an absolute magnitude of 12.5.
- "960 Birgit (A921 TG)". Minor Planet Center. Retrieved 13 February 2020.
- Schmadel, Lutz D. (2007). "(960) Birgit". Dictionary of Minor Planet Names. Springer Berlin Heidelberg. p. 84. doi:10.1007/978-3-540-29925-7_961. ISBN 978-3-540-00238-3.
- "JPL Small-Body Database Browser: 960 Birgit (A921 TG)" (2020-01-04 last obs.). Jet Propulsion Laboratory. Retrieved 13 February 2020.
- "Asteroid 960 Birgit – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 13 February 2020.
- "Asteroid 960 Birgit". Small Bodies Data Ferret. Retrieved 13 February 2020.
- Zappalà, Vincenzo (1995). "Asteroid Dynamical Families – EAR-A-5-DDR-FAMILY-V4.1". NASA Planetary Data System. Retrieved 13 February 2020.
- 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" (PDF). The Astrophysical Journal. 791 (2): 11. arXiv:1406.6645. Bibcode:2014ApJ...791..121M. doi:10.1088/0004-637X/791/2/121. Retrieved 13 February 2020.
- "LCDB Data for (960) Birgit". Asteroid Lightcurve Database (LCDB). Retrieved 13 February 2020.
- Kryszczynska, A.; Colas, F.; Polinska, M.; Hirsch, R.; Ivanova, V.; Apostolovska, G.; et al. (October 2012). "Do Slivan states exist in the Flora family?. I. Photometric survey of the Flora region" (PDF). Astronomy and Astrophysics. 546: 51. Bibcode:2012A&A...546A..72K. doi:10.1051/0004-6361/201219199. Retrieved 13 February 2020. (VizieR)
- Behrend, Raoul. "Asteroids and comets rotation curves – (960) Birgit". Geneva Observatory. Retrieved 13 February 2020.
- Dictionary of Minor Planet Names, Google books
- Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
- Discovery Circumstances: Numbered Minor Planets (1)-(5000) – Minor Planet Center
- 960 Birgit at AstDyS-2, Asteroids—Dynamic Site
- 960 Birgit at the JPL Small-Body Database