1720 Niels

1720 Niels, provisional designation 1935 CQ, is a stony asteroid from the inner regions of the asteroid belt, approximately 6.4 kilometers in diameter. It was discovered on 7 February 1935, by German astronomer Karl Reinmuth at Heidelberg Observatory in southern Germany, and named after a grandson of the discoverer.[2][9]

1720 Niels
Discovery[1]
Discovered byK. Reinmuth
Discovery siteHeidelberg Obs.
Discovery date7 February 1935
Designations
(1720) Niels
Named after
Niels (discoverer's grandson)[2]
1935 CQ · 1940 WH
1951 AL · 1953 VO1
1959 RA · 1963 WE
main-belt · (inner)[3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc89.52 yr (32,697 days)
Aphelion2.4170 AU
Perihelion1.9593 AU
2.1881 AU
Eccentricity0.1046
3.24 yr (1,182 days)
240.21°
Inclination0.7301°
127.86°
308.86°
Physical characteristics
Dimensions6.394±0.091[4]
6.566±0.063 km[5]
8.18 km (calculated)[3]
9.976 h[6]
19.2 h[7]
0.20 (assumed)[3]
0.2154±0.0284[5]
0.227±0.017[4]
LS[8] · S[3]
12.22±0.25[8] · 12.8[1][3] · 13.2[5]

    Orbit and classification

    Niels orbits the Sun in the inner main-belt at a distance of 2.0–2.4 AU once every 3 years and 3 months (1,182 days). Its orbit has an eccentricity of 0.10 and an inclination of 1° with respect to the ecliptic.[1] First observed at Heidelberg in 1927, Niels' observation arc begins with its official discovery observation in 1935.[9]

    Physical characteristics

    Pan-STARRS classifies this stony asteroid as a LS-type, an intermediate to the rare L-type asteroids.[8]

    Rotation period

    A rotational lightcurve of Niels was obtained by astronomer Maurice Clark in December 2005. It gave it a rotation period of 9.976 hours with a brightness variation of 0.15 magnitude (U=1). In November 2008, photometric observations by amateur astronomer Pierre Antonini gave another period of 19.2 hours with an amplitude of 0.01 (U=1-). As of 2017, a secure period for Niels has not yet been obtained.

    Diameter and albedo

    According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Niels measures 6.394 kilometers in diameter, and its surface has an albedo of 0.227,[4] superseding a preliminary result that gave a slightly larger diameter and lower albedo.[5] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 8.18 kilometers based on an absolute magnitude of 12.8.[3]

    Naming

    The minor planet was named by the discoverer after his grandson, Niels. Reinmuth also named 1719 Jens after one of his grandsons.[2] The official naming citation was published by the Minor Planet Center on 20 February 1976 (M.P.C. 3933).[10]

    References
    1. "JPL Small-Body Database Browser: 1720 Niels (1935 CQ)" (2017-05-05 last obs.). Jet Propulsion Laboratory. Retrieved 7 June 2017.
    2. Schmadel, Lutz D. (2007). "(1720) Niels". Dictionary of Minor Planet Names – (1720) Niels. Springer Berlin Heidelberg. pp. 136–137. doi:10.1007/978-3-540-29925-7_1721. ISBN 978-3-540-00238-3.
    3. "LCDB Data for (1720) Niels". Asteroid Lightcurve Database (LCDB). Retrieved 22 December 2016.
    4. 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 22 December 2016.
    5. 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. Clark, Maurice (March 2007). "Lightcurve Results for 1318 Nerina, 222 Lermontov 3015 Candy, 3089 Oujianquan, 3155 Lee, 6410 Fujiwara, 6500 Kodaira, (8290) 1992 NP, 9566 Rykhlova, (42923) 1999 SR18, and 2001 FY". The Minor Planet Bulletin. 34 (1): 19–22. Bibcode:2007MPBu...34...19C. ISSN 1052-8091. Retrieved 22 December 2016.
    7. Behrend, Raoul. "Asteroids and comets rotation curves – (1720) Niels". Geneva Observatory. Retrieved 22 December 2016.
    8. 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 22 December 2016.
    9. "1720 Niels (1935 CQ)". Minor Planet Center. Retrieved 22 December 2016.
    10. Schmadel, Lutz D. "Appendix – Publication Dates of the MPCs". Dictionary of Minor Planet Names – Addendum to Fifth Edition (2006–2008). Springer Berlin Heidelberg. p. 221. doi:10.1007/978-3-642-01965-4. ISBN 978-3-642-01964-7.

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