(8567) 1996 HW1

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(8567) 1996 HW1
(8567) 1996 HW1 image 3D.png
Shape model of 1996 HW1
Discovery [1] [2]
Discovered by Tom Gehrels
Discovery site Steward Observatory
Discovery date23 April 1996
Designations
(8567) 1996 HW1
NEO  · Amor
Orbital characteristics [3]
Epoch 21 November 2025 (JD 2461000.5)
Uncertainty parameter 0
Aphelion 2.96437 AU
Perihelion 1.12697 AU
2.04567 AU
Eccentricity 0.44909
2.92592 y (1068.69 d)
314.321°
0.33686° / d
Inclination 8.44896°
177.0929°
177.282°
Earth  MOID 0.12152 AU
TJupiter 3.652
Physical characteristics
Dimensions 3.78±0.19 × 1.64±0.16 × 1.49±0.22 km [4] : 226  [a]
2.02 km [4] : 226 
Volume 4.34±1.09 km3 [4] : 226  [b]
8.76243±0.00004 h [4] : 226 
281±5° [4] : 226 
−31±5° [4] : 226 
0.156 [3]
Sq-type [5] : 7 
15.36 [3]

    (8567) 1996 HW1 is a near-Earth asteroid (NEA) located in the inner Solar System. It was discovered on 23 April 1996 by astronomer Tom Gehrels at Steward Observatory. It is a contact binary asteroid, with two lobes separated by a distinct "neck"; altogether, the asteroid is on average 2 kilometres (1.2 mi) in diameter. It has a rotation period of 8.76 hours, which is likely gradually slowing because of the YORP effect.

    Contents

    Discovery

    1996 HW1 was discovered on 23 April 1996 by astronomer Tom Gehrels, who was working as a part of the Spacewatch survey at Steward Observatory, Arizona, United States. [2] The asteroid was assigned the provisional designation 1996 HW1 by the Minor Planet Center (MPC), and its discovery was published in a Minor Planet Circular on 2 May 1996. [6] : 115  Once its orbit was sufficiently determined, it was numbered (8567) by the MPC on 11 April 1998. [7] : 56 As of 2025, it remains unnamed. [3]

    Orbit

    1996 HW1 orbits the Sun at an average distance—its semi-major axis—of 2.05 astronomical units (AU), with an orbital period of 2.93 years. It is classified as a near-Earth asteroid; because its orbit lies entirely outside Earth's orbit, it is also classified as an Amor asteroid. [3] [8] Along its orbit, its distance from the Sun varies between 1.13 AU at perihelion to 2.96 AU at aphelion due to its orbital eccentricity of 0.45. Its orbit is inclined by 8.45° with respect to the ecliptic plane. [3]

    Physical characteristics

    1996 HW1 is a contact binary object with dimensions of 3.78 by 1.64 by 1.49 kilometres (2.35 by 1.02 by 0.93 mi) [4] : 217  and an equivalent mean diameter of 2.02 kilometres (1.26 mi). [4] : 226  Its two lobes have an estimated mass ratio of 2:1, and are separated by a prominent neck. [4] : 223, 217 

    Spectroscopic observations of 1996 HW1 show that it is classified as an Sq-type asteroid, with spectral properties between S-type asteroids and Q-type asteroids. [5] : 7  It has a geometric albedo of 0.156, [3] though its visible light albedo is higher at approximately 0.33. [9] : 231  Its spectrum is significantly reddened, indicating that its surface has undergone appreciable space weathering. [5] : 7 

    Spin and evolution

    1996 HW1 has a sidereal rotation period of 8.76 hours, spinning in a retrograde direction with pole ecliptic coordinates of (281°, –31°). Its spin properties were derived from its lightcurve, or variations in its observed brightness, which was additionally supported by radar observations. [4] : 212  Assuming a bulk density of 2.0 g/cm3, the asteroid is spinning slower than its minimum energy state of 7.4 hours, placing its neck under compressive and shear stress. A lower assumed density of 1.43 g/cm3 makes its observed rotation period its minimum energy state, but such a density requires an improbable porosity of 58%. [4] : 222 

    1996 HW1's spin is likely being slowed by the YORP effect, where irregularly shaped asteroids experience a torque by emitting thermal radiation. 1996 HW1's faster rotation period in the past suggests that its two lobes may have been separated in the past as a binary system. The YORP effect slowly removes angular momentum from binary asteroids, though how quickly this leads to the two components merging depends on the mass ratio. Given the mass ratio of 1996 HW1's two lobes, they could have merged in a span of 1 million years (Myr), within the typical 10 Myr dynamical lifetimes of NEAs. [4] : 222–223 

    Notes

    1. ↑ Uncertainties are given as 5, 10, and 15% for the x, y, and z axes, respectively.
    2. ↑ Uncertainty is given as 25%

    References

    1. ↑ "(8567) = 1996 HW1". Minor Planet Center. Retrieved 15 November 2025.{{cite web}}: CS1 maint: url-status (link) (5331 obs)
    2. 1 2 "Asteroid 8567 1996 HW1". NASA. 21 April 2025. Archived from the original on 15 May 2025. Retrieved 16 November 2025.
    3. 1 2 3 4 5 6 7 "JPL Small-Body Database Lookup: 8567 (1996 HW1)" (2023-02-18 last obs.). Jet Propulsion Laboratory . Retrieved 17 November 2025.
    4. 1 2 3 4 5 6 7 8 9 10 11 12 Magri, Christopher; et al. (July 2011). "Radar and photometric observations and shape modeling of contact binary near-Earth Asteroid (8567) 1996 HW1". Icarus. 214 (1): 210–227. Bibcode:2011Icar..214..210M. doi:10.1016/j.icarus.2011.02.019.
    5. 1 2 3 Popescu, M.; Birlan, M.; Binzel, R.; Vernazza, P.; Barucci, A.; Nedelcu, D. A.; DeMeo, F.; Fulchignoni, M. (November 2011). "Spectral properties of eight near-Earth asteroids". Astronomy & Astrophysics. 535. Bibcode:2011A&A...535A..15P. doi:10.1051/0004-6361/201117118. A15.
    6. ↑ "M. P. C. 26947–27146" (PDF). Minor Planet Circulars. Minor Planet Center. 3 May 1996. Retrieved 16 November 2025.
    7. ↑ "M. P. C. 31457–31632" (PDF). Minor Planet Circulars. Minor Planet Center. 11 April 1998. Retrieved 16 November 2025.
    8. ↑ "NEO Groups". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 February 2002. Retrieved 4 June 2012.
    9. ↑ Howell, E. S.; et al. (March 2018). "SHERMAN – A shape-based thermophysical model II. Application to 8567 (1996 HW1)". Icarus. 303. Bibcode:2018Icar..303..220H. doi:10.1016/j.icarus.2017.12.003.
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