(300163) 2006 VW139
288P/2006 VW139
Time-lapse video of 2006 VW139
Discovered bySpacewatch
Discovery siteKitt Peak National Obs.
Discovery date15 November 2006
(300163) 2006 VW139
2006 VW139 · 288P[1]
P/2006 VW139[3]
main-belt[1][2] · (outer)[4]
main-belt comet[3][5]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc16.31 yr (5,958 days)
Aphelion3.6619 AU
Perihelion2.4358 AU
3.0488 AU
5.32 yr (1,944 days)
0° 11m 6.36s / day
Known satellites1[5][6]
Physical characteristics
Dimensions1.8±0.2 km (derived)[6]
3.20 km (calculated)[4]
Mass(6.15±4.85)×1012 kg[6][a]
3,240 hours (135 d)[4]
0.057 (assumed)[4]
C (assumed)[4]
16.2[1][4] · 16.20±0.24[7]

(300163) 2006 VW139, provisional designations 2006 VW139 and P/2006 VW139, as well as periodic cometary number 288P, is a kilometer-sized asteroid from the outer regions of the asteroid belt and the first "binary main-belt comet" ever discovered.

2006 VW139 belongs to the exclusive class of main-belt comets, which display properties of both comets and asteroids. It is also a synchronous binary system and potentially the slowest rotator known to exist. The object was discovered by Spacewatch in 2006. Its binary nature was confirmed by the Hubble Space Telescope in September 2016.[5] Both primary and its minor-planet moon are similar in mass and size, making it a true binary system.[5] The components are estimated to measure 1.8 kilometers in diameter, orbiting each other at a wide separation of 104 kilometers every 135 days.[4][6][8]


2006 VW139 was discovered on 15 November 2006, by the Spacewatch survey at Kitt Peak National Observatory near Tucson, Arizona.[2] The possible cometary activity was seen in November 2011 by Pan-STARRS.[3] Both Spacewatch and Pan-STARRS are asteroid survey projects of NASA's Near Earth Object Observations Program. After the Pan-STARRS observations it was also given a comet designation of 288P.

Orbit and classification

2006 VW139 is a non-family asteroid of the main-belt's background population.[9] It is both a binary asteroid and a main-belt comet, also known as "active asteroid". It orbits the Sun in the outer main-belt at a distance of 2.4–3.7 AU once every 5 years and 4 months (1,944 days; semi-major axis of 3.05 AU). Its orbit has an eccentricity of 0.20 and an inclination of 3° with respect to the ecliptic.[1]

The body's observation arc begins on September 2000, with a precovery taken by the Sloan Digital Sky Survey at Apache Point Observatory, New Mexico, more than six years prior to its official discovery observation by Spacewatch at Kitt Peak.[2]

First binary main-belt comet

2006 VW139 was first observed by the Hubble Space Telescope (HST) in December 2011.[5] It was imaged by HST in September 2016, just before it made its closest approach to the Sun and confirmed its binary nature with two asteroids orbiting each other, and revealed ongoing cometary activity.[8] This makes the object the first known binary asteroid that is also classified as a main-belt comet.[8] The binary is thought to be the result of fission of the precursor caused by YORP-driven spinup.[5]

Observations of the HST revealed ongoing activity in this binary system. The combined features of this binary asteroid - wide separation, near-equal component size, high eccentricity orbit, and comet-like activity also make it unique among the few known binary asteroids that have a wide separation.[5][8]

Physical characteristics

Diameter albedo and mass

2006 VW139 has a derived diameter of 1.8±0.2 kilometer.[6] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.057 and calculates a diameter of 3.20 kilometers based on an absolute magnitude of 16.2.[4] The binary system has an estimated mass between 1.3×1012 kg and 1.1×1013 kg.[5] A single component has a derived mass of (6.15±4.85)×1012 kg.[6]

Numbering and naming

This minor planet was numbered by the Minor Planet Center on 12 October 2011 (M.P.C. 76600).[10] As of 2020, it has not been named.[2]


  1. ^ The mass of the primary component(6.15±4.85)×1012 kg. The overall mass of the binary system is estimated to be between 1.3×1012 kg and 1.1×1013 kg.[5]


  1. ^ a b c d e f "JPL Small-Body Database Browser: 300163 (2006 VW139)" (2016-12-26 last obs.). Jet Propulsion Laboratory. Retrieved 24 November 2017.
  2. ^ a b c d e "(300163) 2006 VW139". Minor Planet Center. Retrieved 30 September 2020.
  3. ^ a b c Hsieh, Henry H.; Yang, Bin; Haghighipour, Nader; Kaluna, Heather M.; Fitzsimmons, Alan; Denneau, Larry; et al. (March 2012). "Discovery of Main-belt Comet P/2006 VW139 by Pan-STARRS1". The Astrophysical Journal Letters. 748 (1): 7. arXiv:1202.2126. Bibcode:2012ApJ...748L..15H. doi:10.1088/2041-8205/748/1/L15. S2CID 8693844.
  4. ^ a b c d e f g h "LCDB Data for (300163)". Asteroid Lightcurve Database (LCDB). Retrieved 24 November 2017.
  5. ^ a b c d e f g h i Agarwal, Jessica; Jewitt, David; Mutchler, Max; Weaver, Harold; Larson, Stephen (September 2017). "A binary main-belt comet". Nature. 549 (7672): 357–359.(NatureHomepage). arXiv:1710.03454. Bibcode:2017Natur.549..357A. doi:10.1038/nature23892. PMID 28933430. S2CID 4469577.
  6. ^ a b c d e f Johnston, Wm. Robert (24 September 2017). "Asteroids with Satellites Database – (300163) 2006 VW139 (= 288P)". Johnston's Archive. Retrieved 24 November 2017.
  7. ^ 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. S2CID 53493339.
  8. ^ a b c d "Comet or Asteroid? Hubble Discovers that a Unique Object is a Binary". NASA. 20 September 2017. Retrieved 28 July 2018.
  9. ^ "Asteroid (300163) 2006 VW139 – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 28 October 2019.
  10. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 24 November 2017.