Known populations of solar system objects: September 2016

compiled by Wm. Robert Johnston
last updated 5 September 2016

For related historical graphs see Historical known populations of solar system objects.

Summary

Star: 1

Planets*: 8
Dwarf planets*: 5 (5 named)
Asteroids*: 715,303 (473,720 numbered**, 241,583 provisional)
Outer solar system objects*: 2,460 (395 numbered**, 2,065 provisional)
Comets***: 5,635 (329 numbered***, 3,598 with provisional designations, 1,708 without official designations)

Moons of planets: 173 (147 named, 2 numbered/unnamed, 24 provisional)
Moons of dwarf planets: 9 (8 named, 1 provisional)
Moons of asteroids: 215 (11 named, 204 provisional)
Moons of outer solar system objects: 77 (12 named, 65 provisional)
Objects with ring systems: 5 (4 planets, 1 Centaur)

* Note: "dwarf planet" is a new classification designated by the International Astronomical Union on 24 August 2006; currently it includes the asteroid (1) Ceres, Pluto, and the trans-Neptunian objects (136108) Haumea, (136199) Eris, (136472) Makemake. These five objects are not included in the counts of asteroids and outer solar system objects, and Pluto is not included in the count of planets.

** Note: numbered asteroids include 20,168 with names, and numbered outer solar system objects include 42 with names. These counts do not include the 5 dwarf planets.

*** Note: excludes two objects with dual designations counted among Centaurs (Chiron and Echeclus) and five objects with dual designations counted among numbered asteroids.


Known populations of solar system objects--detail
object classpermanent designationprovisional designationtotalnotes
   Mercury moons: 0 0 0
   Venus moons: 0 0 0
asteroids, Aten: 194 894 1,088(#1)
   Aten asteroid moons: 0 7 7(#2)
   Earth moons: 1 0 1
asteroids, Earth Trojans: 0 1 1(#3)
asteroids, Apollo: 1,084 6,182 7,266(#4)
   Apollo asteroid moons: 0 39 39(#5)
asteroids, Amor: 960 5,393 6,353(#6)
   Amor asteroid moons: 0 15 15(#7)
   Mars moons: 2 0 2(#8)
asteroids, Mars Trojans: 4 0 4(#9)
   Mars Trojan asteroid moons: 0 1 1(#10)
asteroids, main belt: 466,960227,172694,132(#11)
   Ceres moons: 0 0 0
   main belt asteroid moons: 10 139 149(#12)
comets, Jupiter family: 306 255 561(#13)
   Jupiter moons: 53 14 67(#14)
asteroids, Jupiter Trojans: 4,518 1,939 6,457(#15)
   Jupiter Trojan asteroid moons: 1 3 4(#16)
   Saturn moons: 53 9 62(#17)
   Uranus moons: 27 0 27(#18)
asteroids, Uranus Trojans: 0 1 1(#19)
comets, short period (non-Jupiter family): 23 131 154(#20)
   Neptune moons: 13 1 14(#21)
KBOs, Neptune Trojans: 2 15 17(#22)
Centaurs and scattered disk objects: 153 518 671(#23)
   Centaur/scattered disk object moons: 2 7 9(#24)
Kuiper Belt objects: 239 1,527 1,766(#25)
   Kuiper Belt object moons: 10 58 68(#26)
   Pluto moons: 5 0 5(#27)
   Haumea moons: 2 0 2(#28)
   Makemake moons: 0 1 1(#29)
   Eris moons: 1 0 1(#30)
Sednoids: 1 5 6(#31)
comets, long-period: 3,212 1,708 4,920(#32)

Notes to table:

  1. Asteroids with semimajor axes less than 1.0 AU. First one (2062 Aten) discovered 1976.
  2. First one discovered 1999.
  3. Asteroid orbiting in horseshoe orbits with the Earth. First one (2010 TK7) discovered 2010. Does not include non-Trojan coorbital objects, such as 2002 AA29.
  4. Asteroids (other than Amors) with perihelion distances less than 1.0 AU. First one (1862 Apollo) discovered 1932.
  5. First one discovered 1997.
  6. Asteroids (other than Amors or Apollos) with perihelion distances less than 1.3 AU. First one (433 Eros) discovered 1898.
  7. First one discovered 1997.
  8. First one (Phobos) discovered 1877.
  9. Asteroids orbiting in Mars' L4 and L5 positions (60 degrees ahead of and behind Mars, respectively). First one discovered 1990.
  10. First one discovered 2014.
  11. Asteroids not counted elsewhere (some may cross the orbits of Mars, Jupiter, or other outer planets). Provisional asteroid figures include many objects counted more than once. First one (1 Ceres) discovered 1801 and also now the only one classified as a dwarf planet and thus not counted in this row; first one not designated a dwarf planet (2 Pallas) discovered 1802.
  12. First one discovered 1993.
  13. Comets with Tisserand parameter with respect to Jupiter less than 2 (generally, comets with periods less than 20 years).
  14. First ones (Io, Europa, Ganymede, and Callisto) discovered 1610.
  15. Asteroids orbiting in Jupiter's L4 and L5 positions (60 degrees ahead of and behind Jupiter, respectively). First one discovered 1906.
  16. First one discovered 2001.
  17. First one (Titan) discovered 1655.
  18. First ones (Titania and Oberon) discovered 1787.
  19. First one discovered 2011.
  20. Comets with orbital periods less than 200 years, other than Jupiter family members. Excludes 2 objects with dual designations counted among Centaurs (Chiron and Echeclus).
  21. First one (Triton) discovered 1846.
  22. Outer solar system objects orbiting in Neptune's L4 or L5 positions (60 degrees ahead of or behind Neptune, respectively). First one (2001 QR322) discovered 2001.
  23. Outer solar system objects beyond Saturn outside the main Kuiper Belt. Centaurs and scattered disk objects are included together since different delineations between the two categories exist. First one discovered 1977.
  24. First one discovered 2002.
  25. Outer solar system objects beyond Neptune in the main Kuiper Belt. First one discovered 1995.
  26. First one discovered 2000.
  27. First one (Charon) discovered 1978. Pluto is now classified as a dwarf planet.
  28. First one (Namaka) discovered 2005. Haumea is now classified as a dwarf planet.
  29. First one (S/2015 (136472) 1) discovered 2015. Makemake is now classified as a dwarf planet.
  30. First one (Dysnomia) discovered 2005. Eris is now classified as a dwarf planet.
  31. Outer solar system objects with perihelia greater than 70 AU. First one (90377 Sedna) discovered 2003.
  32. Comets with orbital periods over 200 years. A different criterion for permanent/provisional designations is used in this entry: "permanent" here includes long-period comets with computed orbits and IAU designations; "provisional" includes objects with no IAU designation: ancient comets with no computed orbit (456), modern comets with no computed orbit (105), and recently discovered comets awaiting designations (958).
Counts are up-to-date by category through the following dates: Counts above are primarily based on counts of objects with officially assigned permanet or provisional designations. Exceptions: Note that many (456) of the 1,708 "other" provisional comets are from pre-modern observations and have no computed orbits. Provisional asteroid and comets numbers do not all represent unique objects (i.e. many provisional objects have been counted more than once in as yet unlinked observations).

In August 2006 the IAU reclassified Pluto (a still disputed decision) into a new category of "dwarf planet", along with Eris and Ceres. In July 2008 Makemake was declared the fourth dwarf planet, and in September 2008 Haumea the fifth.

An estimated 220 man-made objects are orbiting the Sun, 1 is orbiting Mercury, 4 are orbiting Venus, 15 are orbiting Mars, 1 is orbiting (1) Ceres, 1 is orbiting Jupiter, 1 is orbiting Saturn, 1 is orbiting comet 67P/Churyumov-Gerasimenko, and 8 are escaping the solar system. This is noteworthy in this context since at least one Apollo "asteroid" with a provisional designation--2010 KQ--might be a spent rocket booster.

Counts are based on data from: the Minor Planet Center web site; The Catalogue of Cometary Orbits 1999 (Marsden and Williams); The Catalogue of Cometary Orbits 2005 (Marsden and Williams); Cometography, Vol. I (Kronk, 1999); International Comet Quarterly web site; the National Space Science Data Center web site; the Solar and Heliospheric Observatory web site; and the web site for the Asteroid Orbital Elements Database (Bowell) on Lowell Observatory's web site.


© 2001-2015, 2016 by Wm. Robert Johnston.
Last updated 5 September 2016.
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