(35107) 1991 VH

(35107) 1991 VH (provisional designation 1991 VH) is a binary near-Earth asteroid and potentially hazardous asteroid of the Apollo group. It was discovered on 9 November 1991, by Australian astronomer Robert McNaught at Siding Spring Observatory. This binary system is composed of a roughly-spheroidal primary body about one kilometre in diameter, and an elongated natural satellite less than half a kilometre in diameter.[5] The 1991 VH system is unusual for its dynamically excited state; the satellite has a tumbling, non-synchronous rotation that chaotically exchanges energy and angular momentum with its precessing, eccentric orbit.[11][6] This asteroid system was one of the two targets of NASA's upcoming Janus Mayhem mission,[12][13] until the delay of the rocket launch made both targets inaccessible.[14]

(35107) 1991 VH
Radar images of 1991 VH and its satellite by Arecibo Observatory in 2008
Discovery[1][2]
Discovered byR. H. McNaught
Discovery siteSiding Spring Obs.
Discovery date9 November 1991
Designations
1991 VH
NEO · Apollo · PHA[3]
Orbital characteristics[3]
Epoch 21 January 2022 (JD 2459600.5)
Uncertainty parameter 0
Observation arc29.34 yr (10,717 days)
Aphelion1.3014 AU
Perihelion0.9732 AU
1.1373 AU
Eccentricity0.1443
1.21 yr (443.02 days)
7.959°
0° 48m 45.357s / day
Inclination13.912°
139.349°
206.940°
Known satellites1
Earth MOID0.02467 AU (3,691,000 km; 9.60 LD)
Physical characteristics[4]
Dimensions1.30 × 1.25 × 1.18 km[5]
Mean diameter
1.18±0.18 km (primary)[5]
Mass(1.58±0.08)×1012 kg (system)[5]
1.4×1012 kg (primary)[lower-alpha 1]
Mean density
1.7±0.8 g/cm3[5]
2.6238±0.0001 h[6][4]
0.17–0.18[5]
Sk (SMASS)[3]
V–R=0.38±0.04[7]
R–I=0.36±0.04[7]
17.02±0.07 (H-G)[lower-alpha 2]
16.76 (assumed)[lower-alpha 3]

    Numbering and naming

    This minor planet was numbered by the Minor Planet Center on 27 February 2002.[15] It has not yet been named.[1]

    Orbit

    1991 VH orbits the Sun at a distance of 0.98–1.30 AU once every 1.21 years (443 days). Its orbit has an eccentricity of 0.14 and an inclination of 14° with respect to the ecliptic.[3]

    Close approaches

    The asteroid has an Earth minimum orbital intersection distance of 0.0247 AU (3.70 million km; 2.30 million mi), which translates into approximately 9.6 lunar distances (LD). It has made multiple close approaches to Earth, with the closest being 0.0458 AU (6.85 million km; 4.26 million mi) or 17.8 LD on 15 August 2008.[3]

    Physical characteristics

    Diameter, shape, and albedo

    High-resolution radar imaging from Goldstone and Arecibo Observatory in 2008 show that the 1991 VH primary is a roughly-spheroidal object with an equatorial ridge, bearing resemblance to a spinning top. This shape is not unique to 1991 VH as it been observed in other near-Earth asteroids; most notably 3200 Phaethon, 66391 Moshup, 101955 Bennu, and 162173 Ryugu.[5][16] A number of topographical features, including a 100 m (330 ft)-wide concavity, are present along the object's equatorial ridge. A bright linear feature casting a shadow at the object's mid- to high-latitudes was also seen in the 2008 radar images.[5]

    Preliminary modeling of the primary's shape in radar images indicates dimensions of 1.30 km × 1.25 km × 1.18 km (0.81 mi × 0.78 mi × 0.73 mi), or a volume-equivalent diameter of 1.18 km (0.73 mi).[5] The geometric albedo for the primary is 0.17–0.18, considerably lower than infrared-based estimates of 0.30–0.40.[8][4]

    Mass and density

    The total mass of the 1991 VH system is (1.58±0.08)×1012 kg, based on the orbital motion of the satellite. The mass ratio of the satellite to the primary is 0.086±0.018, corresponding to a primary mass of 1.4×1012 kg—approximately 12 times as massive as the satellite.[lower-alpha 1] Given the primary mass and diameter, its density is estimated to be about 1.7±0.8 g/cm3, indicative of a rubble pile internal structure.[5][17]

    Spectral type

    In the SMASS taxonomy, 1991 VH is classified as a transitional Sk-type, which is an intermediary between the common stony S-type and the less frequent K-type asteroids.[3]

    Rotation

    Photometric observations in 1997 determined a primary rotation period of 2.624 hours, with a light curve amplitude of 0.08±0.01 magnitudes (U=3).[7] Later photometric observations from 2003–2020 corroborated this result down to a precision of ±0.0001 seconds.[4][18]

    Satellite
    S/2008 (35107) 1
    Radar images of S/2008 (35107) 1 by Arecibo Observatory on 12 August 2008
    Discovery[19][20]
    Discovered byP. Pravec
    M. Wolf
    L. Šarounová
    Discovery siteOndřejov Obs.
    Discovery date27 February 1997
    Designations
    S/1997 (35107) 1[3]
    Orbital characteristics[5]
    3.32±0.07 km
    Eccentricity0.05±0.02[6][9]
    32.57±0.3 h
    (1.357±0.012 d)
    Inclination148°±9°
    (wrt ecliptic)[3][9]
    270°±30°[3][9]
    Physical characteristics
    Dimensionsa/b = 1.33±0.10[21]
    Mean diameter
    		0.42±0.08 km[22]
    (Ds/Dp=0.40±0.02)[9]
    Mass1.4×1011 kg[lower-alpha 4]
    11–16 h (chaotic)[6]
    17.2 (Δmag=0.2)[20]

      S/2008 (35107) 1 is the secondary component and natural satellite of the 1991 VH system.

      Discovery

      S/2008 (35107) 1 is among the first near-Earth asteroid satellites discovered, alongside those of (385186) 1994 AW1 and 3671 Dionysus.[7] It was discovered on 27 February 1997, by astronomers Petr Pravec, Marek Wolf, and Lenka Šarounová at Ondřejov Observatory. The satellite was detected through photometric observations of periodic dips in the system's brightness, caused by mutual eclipses and occultations of the components.[19] The discovery of the satellite was reported in a notice published by the International Astronomical Union on 29 March 1997, but was not officially confirmed until it was individually resolved in adaptive optics imaging by the Keck II telescope at Mauna Kea Observatory on 9 August 2008. The satellite was given the provisional designation S/2008 (35107) 1 on 19 September 2008.[20][22]

      Origin

      As with many binary near-Earth asteroids, the 1991 VH system is thought to have formed through rotational fissioning of a progenitor body due to spin-up by the YORP effect. The resulting mass shed from the progenitor body coalesced in orbit to form the satellite.[17]

      Exploration
      Main article: Janus (spacecraft)

      This asteroid system was the target of NASA's upcoming Janus Mayhem mission, which was planned to launch in 2022 alongside NASA's Psyche spacecraft, and to arrive in 2026.[12][13] 1991 VH became impossible to reach for Janus when the launch of Psyche got delayed in May 2022.[14]

      See also
      • (175706) 1996 FG3, binary near-Earth asteroid and former target of the Janus Serenity mission, until it became inaccessible due to the launch delay

      Notes
      1. Primary mass is calculated from the difference between the system mass and secondary mass: 1.44×1012 kg ≈ 1.58×1012 kg – (0.086 × 1.58×1012 kg).
      2. Nugent et al's two-parameter H-G model of near-infrared WISE photometry takes the asteroid's observed opposition surge behavior into account, yielding an absolute magnitude of H = 17.02 and a slope parameter of G = 0.24.[8] An earlier analysis by Pravec et al. used R-band photometry from 2003 observations and obtained similar results: H = 16.95±0.07 and G = 0.26±0.04[9]
      3. Default fit of photometry from the Minor Planet Center's observations database, assuming a slope parameter of G = 0.15.[1] Because this assumption does not take the asteroid's actual opposition surge behavior into account, the absolute magnitude value H is underestimated.[10]
      4. Secondary mass is calculated from the product of the system mass and secondary/primary mass ratio: 1.4×1011 kg ≈ 0.086 × 1.58×1012 kg.

      References
      1. "(35107) = 1991 VH". Minor Planet Center. International Astronomical Union. Retrieved 17 November 2021.
      2. Green, Daniel W. E. (18 November 1991). "IAUC 5390: 1991 VH". International Astronomical Union Circular. Central Bureau for Astronomical Telegrams. Bibcode:1991IAUC.5390....1M. Retrieved 17 November 2021.
      3. "JPL Small-Body Database Browser: 35107 (1991 VH)" (2021-03-13 last obs.). Jet Propulsion Laboratory. Retrieved 17 November 2021.
      4. "LCDB Data for (35107) 1991 VH". Asteroid Lightcurve Database. Retrieved 18 November 2021.
      5. Naidu, Shantanu; Margot, Jean-Luc; Benner, Lance; Taylor, Patrick A.; Nolan, Michael C.; Magri, Chris; et al. (October 2018). Radar Observations and Characterization of Binary Near-Earth Asteroid (35107) 1991 VH (PDF). 50rd Annual DPS Meeting. American Astronomical Society. Bibcode:2018DPS....5031209N. 312.09. Archived from the original (PDF) on 11 May 2022.
      6. Pravec, P.; Scheeres, D. J.; McMahon, J. W.; Meyer, A. J.; Kušnirák, P.; Hornoch, K.; et al. (27 April 2021). Photometric observations of the unrelaxed binary near-Earth asteroid (35107) 1991 VH in support of the NASA Janus space mission – Detection of a spin-orbit interaction (PDF). 7th IAA Planetary Defense Conference. International Academy of Astronautics.
      7. Pravec, Petr; Wolf, Marek; Šarounová, Lenka (May 1998). "Occultation/Eclipse Events in Binary Asteroid 1991 VH". Icarus. 133 (1): 79–88. Bibcode:1998Icar..133...79P. doi:10.1006/icar.1998.5890. S2CID 120621640.
      8. Nugent, C. R.; Mainzer, A.; Kušnirák, P.; Hornoch, K.; Galád, A.; Naidu, S. P.; 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. S2CID 119289027. 63.
      9. Pravec, P.; Scheirich, P.; Kušnirák, P.; Šarounová, L.; Mottola, S.; Hahn, G.; et al. (March 2006). "Photometric survey of binary near-Earth asteroids". Icarus. 181 (1): 63–93. Bibcode:2006Icar..181...63P. doi:10.1016/j.icarus.2005.10.014. S2CID 121896605.
      10. Pravec, Petr; Harris, Alan W.; Kušnirák, 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. S2CID 123017048.
      11. Naidu, Shantanu P.; Margot, Jean-Luc (February 2015). "Near-Earth Asteroid Satellite Spins Under Spin-orbit Coupling". The Astronomical Journal. 149 (2): 11. arXiv:1410.0082. Bibcode:2015AJ....149...80N. doi:10.1088/0004-6256/149/2/80. OSTI 22342100. S2CID 53630711. 80.
      12. Scheeres, D. J.; McMahon, J. W.; Bierhaus, E. B.; Wood, J.; Benner, L. A. M.; Hartzell, C. M.; et al. (October 2018). Janus: A NASA SIMPLEx mission to explore two NEO Binary Asteroids (PDF). 52nd Lunar and Planetary Science Conference. Lunar and Planetary Institute. Bibcode:2021LPI....52.1706S. 1706.
      13. Sorli, K. C.; Hayne, P.; Scheeres, D.; McMahon, J.; Pravec, P.; Naidu, S.; et al. (October 2020). Thermophysical Modeling of Binary Asteroid Systems for the Janus Mission. 52nd Annual DPS Meeting. Vol. 52. American Astronomical Society. Bibcode:2020DPS....5221707S. 217.07.
      14. Foust, Jeff (9 June 2022). "Psyche launch delay forcing revamp of rideshare mission". spacenews.com. Retrieved 11 June 2022.
      15. "M.P.C. 44864" (PDF). Minor Planet Circulars. Minor Planet Center. 27 February 2002. p. 182. Retrieved 19 November 2021.
      16. MacLennan, Eric; Marshall, Sean; Granvik, Mikael (31 December 2022). "Evidence of surface heterogeneity on active asteroid (3200) Phaethon". Icarus. 388: 115226. doi:10.1016/j.icarus.2022.115226.
      17. Fang, Julia; Margot, Jean-Luc (January 2012). "Near-Earth Binaries and Triples: Origin and Evolution of Spin-Orbital Properties". The Astronomical Journal. 143 (1): 14. arXiv:1111.2794. Bibcode:2012AJ....143...24F. doi:10.1088/0004-6256/143/1/24. S2CID 39176783. 24.
      18. Vander Haagen, Gary A. (January 2010). "(35107) 1991 VH: An Apollo Binary Asteroid". The Minor Planet Bulletin. 37 (1): 36. Bibcode:2010MPBu...37...36V.
      19. Green, Daniel W. E. (29 March 1997). "IAUC 6607: C/1995 O1; 1991 VH". International Astronomical Union Circular. Central Bureau for Astronomical Telegrams. Bibcode:1997IAUC.6607....2P. Retrieved 17 November 2021.
      20. Green, Daniel W. E. (19 September 2008). "IAUC 8977: C/2008 S1; S/2008 (35107) 1". International Astronomical Union Circular. Central Bureau for Astronomical Telegrams. Bibcode:2008IAUC.8977....2M. Retrieved 17 November 2021.
      21. Pravec, P.; Scheirich, P.; Kušnirák, P.; Hornoch, K.; Galád, A.; Naidu, S. P.; et al. (March 2016). "Binary asteroid population. 3. Secondary rotations and elongations" (PDF). Icarus. 267: 267–295. Bibcode:2016Icar..267..267P. doi:10.1016/j.icarus.2015.12.019. S2CID 123330211.
      22. Johnston, Wm. Robert (21 September 2014). "(35107) 1991 VH and S/2008 (35107) 1". Asteroids with Satellites Database. Johnston's Archive. Retrieved 18 November 2021.
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