Known populations of solar system objects: November 2005

compiled by Wm. Robert Johnston
last updated 24 November 2005

Summary

Star: 1
Planets: 9 *
Moons of planets: 159 (116 numbered, 53 provisional) *
Asteroids: 298,661 (118,047 numbered [including 12,691 named], 180,614 provisional)
Moons of asteroids: 57 (5 named, 52 provisional)
Outer solar system objects: 1,072 (114 numbered [including 21 named], 958 provisional) *
Moons of outer solar system objects: 22 (22 provisional) *
Comets: 2,857 (173 numbered, 2,190 with designations, 494 without designations)

Note: these figures count 2003 UB313 (which has one satellite) as an outer solar system object; 2003 UB313 is larger than Pluto, but the IAU has yet to decide its designation.

Known populations of solar system objects--detail
object classpermanent designationprovisional designationtotalnotes
   Mercury moons: 0 0 0
   Venus moons: 0 0 0
asteroids, Aten: 28 274 302(#1)
   Aten asteroid moons: 0 5 5(#2)
   Earth moons: 1 0 1
asteroids, Earth coorbitals: 0 1 1(#3)
asteroids, Apollo: 195 1,566 1,761(#4)
   Apollo asteroid moons: 0 12 12(#5)
asteroids, Amor: 201 1,365 1,566(#6)
   Amor asteroid moons: 0 7 7(#7)
   Mars moons: 2 0 2(#8)
asteroids, Mars Trojans: 1 3 4(#9)
asteroids, main belt: 116,614176,586293,200(#10)
   main belt asteroid moons: 5 27 32(#11)
   Jupiter moons: 48 15 63(#12)
asteroids, Jupiter Trojans: 1,008 819 1,827(#13)
   Jupiter Trojan asteroid moons: 0 1 1(#14)
   Saturn moons: 35 15 50(#15)
   Uranus moons: 21 6 27(#16)
Centaurs: 18 38 56(#17)
comets, short period: 173 199 372(#18)
   Neptune moons: 8 5 13(#19)
KBOs, Neptune Trojans: 0 2 2(#20)
   Pluto moons: 1 2 3(#21)
Kuiper Belt objects: 70 844 914(#22)
   Kuiper Belt object moons: 0 22 22(#23)
scattered disk objects: 26 73 99(#24)
comets, long-period: 1,991 494 2,485(#25)
Oort cloud objects: 1 0 1(#26)

Notes to table:

  1. Asteroids with semimajor axes less than 1.0 AU. First one discovered 1954.
  2. First one discovered 1999.
  3. Asteroid orbiting in horseshoe orbits with the Earth. First one (2002 AA29) discovered 2002. Does not include 2 possible coorbital objects.
  4. Asteroids (other than Amors) with perihelion distances less than 1.0 AU. First one discovered 1932.
  5. First one discovered 1997.
  6. Asteroids (other than Amors or Apollos) with perihelion distances less than 1.3 AU. First one discovered 1898.
  7. First one discovered 1997.
  8. First one discovered 1877.
  9. Asteroids orbiting in Mars' L4 and L5 positions (60 degrees ahead of and behind Mars, respectively). First one discovered 1990.
  10. 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 discovered 1801.
  11. First one discovered 1993.
  12. First one discovered 1610. Does not include 7 objects observed near Amalthea in 2002.
  13. Asteroids orbiting in Jupiter's L4 and L5 positions (60 degrees ahead of and behind Jupiter, respectively). First one discovered 1906.
  14. First one discovered 2001.
  15. First one discovered 1655. Includes several provisional objects which may be clumps of ring material.
  16. First one discovered 1787.
  17. Minor planets with perihelion distances beyond Jupiter and semimajor axes within Neptune's orbit. First one discovered 1977.
  18. Comets with orbital periods less than 200 years.
  19. First one discovered 1846.
  20. 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. Does not include 3 possible coorbital objects discovered in 2005
  21. First one discovered 1978.
  22. Minor planets with semimajor axes beyond Neptune but less than 50 AU; this is the main Kupier belt. First one discovered 1992.
  23. First one discovered 2000.
  24. Minor planets with semimajor axes beyond 50 AU, plus those with semimajor axes from the orbit of Neptune to 50 AU but with perihelion distances less than 25 AU. All known examples have perihelion distances within 50 AU. First one discovered 1995.
  25. 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 ancient comets and others observed with no computed orbit.
  26. Outer solar system objects with perihelia greater than 70 AU. First one (90377 Sedna) discovered 2003.
Counts are up-to-date by category through the following dates: Note that most of the 494 "other" 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).

Discovery of 2003 UB313 was announced in 2005. This trans-Neptunian object is larger than Pluto and has one known satellite. The IAU has not yet determined whether it will be counted as a planet or a minor planet (outer solar system object).

An estimated 177 man-made objects are orbiting the Sun, 5 are orbiting Venus, 13 are orbiting Mars, 1 is near asteroid (25143) Itokawa, 1 is orbiting Saturn, and 4 are beyond the Kupier Belt escaping the solar system. (This is worth noting in this context because two Apollo "asteroids" with provisional designations--1991 VG and 2000 SG344--are suspected of being spent rocket boosters.)

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.

© 2001-2004, 2005 by Wm. Robert Johnston.
Last updated 24 November 2005.
Return to Home. Return to Astronomy and Space.