6084 Bascom

6084 Bascom, provisional designation 1985 CT, is a binary[lower-alpha 1] Phocaea asteroid from the inner regions of the asteroid belt, approximately 6.3 kilometers in diameter. It was discovered on 12 February 1985, by American astronomer couple Carolyn and Eugene Shoemaker at Palomar Observatory in California.[12] It is named after American geologist Florence Bascom.[2] Its satellite measures approximately 2.3 kilometers (0.37 Ds/Dp) and has an orbital period of 43.51 hours.[5]

6084 Bascom
Discovery [1]
Discovered byC. S. Shoemaker
E. M. Shoemaker
Discovery sitePalomar Obs.
Discovery date12 February 1985
Designations
(6084) Bascom
Named after
Florence Bascom
(American geologist)[2]
1985 CT · 1978 EC6
1992 BM1
main-belt · Phocaea [3][4]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc67.22 yr (24,553 days)
Aphelion2.8582 AU
Perihelion1.7697 AU
2.3139 AU
Eccentricity0.2352
3.52 yr (1,286 days)
163.37°
0° 16m 48s / day
Inclination22.999°
147.24°
258.81°
Known satellites1 (P: 43.5 h; 0.37 Ds/Dp)[5][lower-alpha 1]
Physical characteristics
Dimensions6.17±1.15 km[6]
6.347±0.218 km[7][8]
6.388 km[9]
6.39 km (taken)[3]
2.74516±0.00002 h[10]
2.7454±0.0005 h[5]
2.74542 h[3]
2.74544±0.00002 h[lower-alpha 2]
0.2091[3][9]
0.220±0.030[7][8]
0.26±0.10[6]
S [3]
12.8±0.1 (R)[5] · 12.80±0.03 (R)[10] · 12.9[1] · 12.91±0.34[11] · 13.19[6] · 13.25[7] · 13.29±0.058[3][9]

    Orbit and classification

    Bascom is a stony S-type asteroid and member of the Phocaea family (701),[4] a group of asteroids with similar orbital characteristics. It orbits the Sun in the inner main-belt at a distance of 1.8–2.9 AU once every 3 years and 6 months (1,286 days). Its orbit has an eccentricity of 0.24 and an inclination of 23° with respect to the ecliptic.[1] A first precovery was taken at Palomar in 1950, extending the body's observation arc by 30 years prior to its official discovery observation.[12]

    Diameter

    According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Bascom measures 6.17 and 6.347 kilometers in diameter and its surface has an albedo of 0.22 and 0.26, respectively.[6][7][8] The Collaborative Asteroid Lightcurve Link (CALL) adopts Petr Pravec's revised WISE-data, that is, an albedo of 0.2091 and a diameter of 6.39 kilometers for an absolute magnitude of 13.29.[3][9]

    Moon and lightcurve

    Between 29 December 2005 and 2 February 2006, the first ever rotational lightcurve was obtained from photometric observations taken by astronomers David Higgins at Hunters Hill Observatory, Australia, by Petr Pravec, Peter Kušnirák, and Lenka Šarounová at Ondřejov Observatory, Czech Republic, and by Štefan Gajdoš, Adrián Galád and Jozef Világi at Modra Observatory, Slovakia.[5][lower-alpha 1]

    The observations revealed, that Bascom is a synchronous binary asteroid that has a moon orbiting its primary every 43.5 hours. Mutual asteroid occulation and eclipsing events with a magnitude between 0.12 and 0.18 suggest, that the satellite's diameter is 37±2% of that of Bascom (a secondary-to-primary diameter ratio of 0.37), which translates into a mean-diameter of 2.3 kilometers for the minor-planet moon. The photometric observations had an average absolute magnitude of 12.8.[5][lower-alpha 1]

    Since Bascom's first observation in December 2005, astronomer Peter Pravec has obtained additional lightcurves. They gave a refined rotation period for the primary of 2.74516 to 2.74544 hours with a brightness variation between 0.14 and 0.23 magnitude (U=3/3/3).[10][lower-alpha 2] These observations also confirmed the presence of the satellite giving a concurring orbital period of 43.51 hours.[10] For an asteroid of its size, Bascom has a relatively fast spin rate, but still above those of fast rotators. CALL adopts a rotation period of 2.74542 hours.[3]

    Naming

    This minor planet was named in memory of Florence Bascom (1862–1945), the second woman to earn her Ph.D in geology in the United States. She was also the first woman hired by the United States Geological Survey and the first woman elected to the Council of the Geological Society of America. Bascom founded the geology department at Bryn Mawr College, Pennsylvania, where she taught the next generation of notable female geologists for 33 years. Expert in petrography, mineralogy and crystallography, her research focused on geomorphology.[2] The approved naming citation was published by the Minor Planet Center on 11 April 1998 (M.P.C. 31610).[13]

    Notes
    1. Central Bureau for Astronomical Telegrams – CBET No. 389
      Photometric observations obtained between 29 December 2005 and 2 February 2006, reveal, that 6084 Bascom is a binary system with an orbital period of 43.5 hours. The primary rotates with a period of 2.7454 hours. The lightcurve's amplitude is 0.22 magnitude. Mutual eclipse and occultation events between 0.12 and 0.18 magnitude, suggest a secondary-to-primary mean-diameter ratio of 0.37±0.02. The system's mean absolute R magnitude is 12.8±0.1.
      Reported by: David Higgins (Hunters Hill Obs., Canberra, Australia), Petr Pravec, Peter Kušnirák, and Lenka Šarounová (Ondřejov Obs., Czech Republic) and Štefan Gajdoš, Adrián Galád and Jozef Világi (Modra Obs., Slovakia)
    2. Pravec (2013) web: rotation period 2.74544±0.00002 hours with a brightness amplitude of 0.23 mag. Summary figures at Collaborative Asteroid Lightcurve Link and Ondrejov Asteroid Photometry Project

    References
    1. "JPL Small-Body Database Browser: 6084 Bascom (1985 CT)" (2017-06-06 last obs.). Jet Propulsion Laboratory. Retrieved 4 July 2017.
    2. Schmadel, Lutz D. (2007). "(6084) Bascom". Dictionary of Minor Planet Names – (6084) Bascom. Springer Berlin Heidelberg. pp. 508–509. doi:10.1007/978-3-540-29925-7_5637. ISBN 978-3-540-00238-3.
    3. "LCDB Data for (6084) Bascom". Asteroid Lightcurve Database (LCDB). Retrieved 15 March 2017.
    4. "Asteroid 6084 Bascom – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
    5. Higgins, D.; Pravec, P.; Kusnirak, P.; Sarounova, L.; Gajdos, S.; Galad, A.; et al. (February 2006). "(6084) Bascom". Central Bureau Electronic Telegrams. 389 (389): 1. Bibcode:2006CBET..389....1H. Retrieved 15 March 2017.
    6. 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 15 March 2017.
    7. 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.
    8. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 15 March 2017.
    9. Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026. Retrieved 15 March 2017.
    10. Pravec, P.; Scheirich, P.; Vokrouhlický, D.; Harris, A. W.; Kusnirák, P.; Hornoch, K.; et al. (March 2012). "Binary asteroid population. 2. Anisotropic distribution of orbit poles of small, inner main-belt binaries". Icarus. 218 (1): 125–143. Bibcode:2012Icar..218..125P. doi:10.1016/j.icarus.2011.11.026. Retrieved 15 March 2017.
    11. 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 15 March 2017.
    12. "6084 Bascom (1985 CT)". Minor Planet Center. Retrieved 15 March 2017.
    13. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 15 March 2017.

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