Since the year 2000, a number of Kuiper belt objects (KBOs) with diameters of between 500 and 1500 km (more than half that of Pluto) have been discovered. 50000 Quaoar, a classical KBO discovered in 2002, is over 1200 km across. Makemake and Haumea, both announced on 29 July 2005, are larger still. Other objects, such as 28978 Ixion (discovered in 2001) and 20000 Varuna (discovered in 2000) measure roughly 500 km across.[1] This has led gradually to the acceptance of Pluto as the largest member of the Kuiper belt.
The brightest known KBOs (with absolute magnitudes < 4.0), are:
Permanent Designation |
Provisional Designation |
Absolute magnitude | Albedo (%)[2] | Equatorial diameter (km)[2] |
Semimajor axis (AU) |
Date found | Discoverer | Diameter method |
---|---|---|---|---|---|---|---|---|
Pluto[3] | -1.0 | 60 | 2320. | 39.4 | 1930 | C. Tombaugh | occultation | |
Makemake | 2005 FY9[4] | -0.3 | 80. +10.−20. | 1500. -200+400 | 45.7 | 2005 | M. Brown, C. Trujillo & D. Rabinowitz | Thermal |
Haumea | 2003 EL61[5] | 0.1 | 84. +10−20 | 1150. -100+250 | 43.3 | 2005 | Sierra Nevada Observatory, Spain[6] | Thermal |
Charon[7] | S/1978 P 1 | 1 | 40 | 1205. | 39.4 | 1978 | J. Christy | occultation |
Orcus | 2004 DW | 2.3 | 19.72 +3.40−2.76 | 946.3 -72.3+74.1 | 39.4 | 2004 | M. Brown, C. Trujillo & D. Rabinowitz | Thermal |
Quaoar | 2002 LM60 | 2.6 | 19.9 +13.2−7. | 844. -190+207 / 1260 ± 190 | 43.5 | 2002 | C. Trujillo & M. Brown | Disk resolved/thermal |
Ixion | 2001 KX76 | 3.2 | 12 +14−6 | 650. -220+260 | 39.6 | 2001 | DES | Thermal |
55636 | 2002 TX300 | 3.3 | 10. or more | 800. or less | 43.1 | 2002 | NEAT | Thermal |
55565 | 2002 AW197 | 3.3 | 11.77 +4.42−3.00 | 734.6 -108.3+116.4 | 47.4 | 2002 | C. Trujillo, M. Brown, E. Helin, Steven H. Pravdo, K. Lawrence & Michael D. Hicks; Palomar Observatory |
Thermal |
55637 | 2002 UX25 | 3.6 | 11.50 +5.09−3.09 | 681.2 -114.0+115.6 | 42.5 | 2002 | Anne S. Descour; Spacewatch | Thermal |
Varuna | 2000 WR106 | 3.7 | 16. +10−8 | 500. -100+100 | 43.0 | 2000 | R. McMillan | Thermal |
2002 MS4 | 3.8 | 08.41 +3.78−2.26 | 726.2 -122.9+123.2 | 41.8 | 2002 | C. Trujillo, M. Brown | Thermal | |
2003 AZ84[8] | 3.9 | 12.32 +4.31−2.91 | 685.8 -95.5+98.8 | 39.6 | 2003 | C. Trujillo, M. Brown, E. Helin, Steven H. Pravdo, K. Lawrence & Michael D. Hicks |
Thermal |