4979 Otawara

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4979 Otawara
Discovery [1]
Discovered by K. W. Reinmuth
Discovery site Heidelberg
Discovery date2 August 1949
Designations
(4979) Otawara
Named after
Akira Otawara [2]
1949 PQ ·1977 DW10 ·1978 TY5 ·1978 SW4 [1]
main belt
Orbital characteristics [3]
Epoch 5 May 2025 (JD 2460800.5)
Uncertainty parameter 0
Observation arc 27736 days (75.94 yr)
Aphelion 2.483 AU
Perihelion 1.852 AU
2.167 AU
Eccentricity 0.1453
3.191 yr (1166 d)
298.626°
0° 18m 32.04s / day
Inclination 0.9092°
69.799°
206.956°
Earth  MOID 0.8363 AU
Physical characteristics
Dimensions ~3.204 km (JPL) [3]
2.6–4.0 km (Doressoundiram et al. 1999) [4] : 702  [a]
Mean density
≥1.9 g/cm3 [4] : 702  [b]
2.707±0.005 h [5] : 662 
50±5° or 230±5° [6]
−30±16° [6]
S-type [7] : 330 
14.43 (JPL) [3]

    4979 Otawara (provisional designation: 1949 PQ) is a small, rapidly rotating asteroid orbiting in the main asteroid belt. Discovered in 1949, the asteroid was named after Japanese photo artist and writer Akira Otawara. It is stony in composition, consisting of olivine and pyroxenes, and is estimated to be around 2–4 kilometres (1.2–2.5 mi) in size. The asteroid was one of three originally planned targets for the Rosetta mission, but launch delays meant that it was abandoned.

    Contents

    Discovery and naming

    Otawara was discovered on 2 August 1949 by German astronomer Karl Wilhelm Reinmuth, in Heidelberg. It was given the provisional designation 1949 PQ, [1] and on 21 November 1991 it was numbered 4979 by the Minor Planet Center. [8] The asteroid was named after Akira Otawara, a photo artist and writer. Together with astronomer Shuichi Nakano, he published two catalogs in 1983, Field Star Map 2000 and Star & Planet Catalogue 2000. Nakano proposed the name Otawara for the object; the name was published in Minor Planet Circular 22505 on 1 September 1993. [2]

    Orbit

    A diagram of 4979 Otawara's orbit, with the orbits of the inner planets and Jupiter shown. 4979 Otawara orbit.png
    A diagram of 4979 Otawara's orbit, with the orbits of the inner planets and Jupiter shown.

    Otawara orbits with a semi-major axis of 2.17 astronomical units (AU); [3] it is located in the main asteroid belt. [7] : 328  It has a moderate orbital eccentricity of 0.15. Along its 3.19 year (1166 day) orbit, its distance from the Sun varies from 1.85 AU at perihelion to 2.48 AU at aphelion. Its orbit is closely aligned with the plane of the planets, with an orbital inclination of 0.91° with respect to the ecliptic plane. [3]

    Physical characteristics

    Otawara is a small asteroid; [4] : 702  estimates of its size range around 2–4 kilometres (1.2–2.5 mi). [a] Otawara's lightcurve, or variations in its observed apparent brightness, suggests that it is elongated, with an a/b axis ratio of 1.21±0.05. [6] [7] : 330  Initial analysis of Otawara's spectrum in 1999, conducted by a team of astronomers led by Alain Doressoundiram, was ambiguous on what asteroid taxonomic class it belonged to. [7] : 330  Its spectrum was consistent with either an S-type asteroid rich in silicate minerals, a V-type asteroid associated with 4 Vesta, or an SV-type asteroid, with characteristics intermediate of the two. [4] : 702  However, later analysis by a team led by Sonia Fornasier ruled out a V-type classification, and concluded that Otawara is an S-class asteroid rich in olivine and pyroxenes. Under the Gaffey classification scheme, Otawara belongs to the S(IV) subclass. S(IV) asteroids are probable candidates for parent bodies of ordinary chondrite meteorites; Otawara's spectral similarity to these meteorites suggests it is not differentiated. [7] : 330–333  Otawara's density is constrained to be ≥1.9 g/cm3, although this is not valid if it is a solid object instead of a rubble pile. [4] : 702 

    Analysis of Otawara's lightcurve suggests it rotates rapidly, with a rotation period of 2.707±0.005 hours, classifying it as a fast rotating asteroid. [7] : 329  [4] : 701  Its rotation appears to be retrograde—rotating clockwise—with its north pole pointed towards the ecliptic south. [7] : 330  [6]

    Exploration

    Otawara, along with 140 Siwa, was planned as a flyby target for the European Space Agency's Rosetta spacecraft mission on its way to comet 46P/Wirtanen. Expected to encounter Otawara on 11 July 2006, Rosetta would have been able to image most of its surface due to its rotation. Rosetta would have been unable to measure Otawara's mass due to its small size and the spacecraft's flyby geometry. [9] [10] : 1122, 1127 Rosetta was originally set to launch in January 2003, but the failure of an Ariane 5 rocket postponed the spacecraft's launch and forced the ESA to find new targets. [11] [12] : ix Rosetta eventually launched successfully in 2004, visiting the main belt asteroids 2867 Šteins and 21 Lutetia before arriving at its newly selected primary target 67P/Churyumov–Gerasimenko. [13] [14]

    Notes

    1. 1 2 Doressoundiram et al. (1999) estimated Otawara's circular effective radii as 2.0 km for an S-type albedo and 1.3 km for a V-type albedo. [4] : 702  JPL gives a value of 3.204 km for Otawara's diameter. [3]
    2. ↑ Assuming Otawara is a rubble pile asteroid.

    References

    1. 1 2 3 "(4979) Otawara = 1978 TY5 = 1949 PQ = 1978 SW4 = 1977 DW10". Minor Planet Center. Archived from the original on 23 February 2025. Retrieved 25 August 2025.
    2. 1 2 "M. P. S. 22505" (PDF). Minor Planet Circulars Supplement. Minor Planet Center. 1 September 1993. p. 73. Archived (PDF) from the original on 4 March 2016. Retrieved 25 August 2025.
    3. 1 2 3 4 5 6 "4979 Otawara (1949 PQ)". JPL Small-Body Database . NASA/Jet Propulsion Laboratory. Archived from the original on 1 March 2023. Retrieved 25 August 2025.
    4. 1 2 3 4 5 6 7 Doressoundiram, A.; et al. (December 1999). "4979 Otawara: flyby target of the Rosetta mission". Astronomy and Astrophysics. 352: 697–702. Bibcode:1999A&A...352..697D.
    5. ↑ Le Bras, A.; Dotto, E.; Fulchignoni, M.; Doressoundiram, A.; Barucci, M. A.; Le Mouélic, S.; Forni, O.; Quirico, E. (November 2001). "The 2000 Rosetta asteroid targets observational campaign: 140 Siwa and 4979 Otawa". Astronomy and Astrophysics. 379: 660–663. Bibcode:2001A&A...379..660L. doi:10.1051/0004-6361:20011327.
    6. 1 2 3 4 Fauvaud, Stephane; Fauvaud, Marcel; Paschke, Anton (December 2003). "CCD photometric observations of the minor planet 4979 Otawara". The Minor Planet Bulletin. 30 (4): 73. Bibcode:2003MPBu...30...73F.
    7. 1 2 3 4 5 6 7 Fournasier, S.; et al. (January 2003). "A portrait of 4979 Otawara, target of the Rosetta space mission". Astronomy and Astrophysics. 398: 327–33. Bibcode:2003A&A...398..327F. doi:10.1051/0004-6361:20021622.
    8. ↑ "M. P. S. 19275" (PDF). Minor Planet Circulars Supplement. Minor Planet Center. 21 November 1991. p. 221. Archived (PDF) from the original on 25 September 2023. Retrieved 25 August 2025.
    9. ↑ "Debris of the Solar System: asteroids Otawara and Siwa". European Space Agency. 22 November 2002. Archived from the original on 29 September 2024. Retrieved 28 August 2025.
    10. ↑ Pätzold, M.; Wennmacher, A.; Häusler, B.; Eidel, W.; Morley, T.; Thomas, N.; Anderson, J. D. (May 2001). "Mass and density determinations of 140 Siwa and 4979 Otawara as expected from the Rosetta flybys". Astronomy and Astrophysics. 370: 1122–1127. Bibcode:2001A&A...370.1122P. doi:10.1051/0004-6361:20010244.
    11. ↑ Schilling, Govert (14 January 2003). "Rosetta Probe Won't Launch". Science. Retrieved 28 August 2025.
    12. ↑ Colangeli, Luigi; Mazzotta Epifani, Elena; Palumbo, Pasquale, eds. (2004). The New Rosetta Targets (1 ed.). Springer Dordrecht. doi:10.1007/978-1-4020-2573-0. ISBN   978-1-4020-2572-3.
    13. ↑ "Steins: A diamond in the sky". ESA. 6 September 2008. Retrieved 28 August 2025.
    14. ↑ "Rosetta triumphs at asteroid Lutetia". ESA. 10 July 2010. Archived from the original on 20 July 2025. Retrieved 28 August 2025.
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