TNO/Centaur diameters and albedos

compiled by Wm. Robert Johnston
last modified 17 September 2008

The first trans-Neptunian object (TNO) was discovered in 1992. Given the remoteness of TNOs, it was years before sizes were first measured for a few TNOs. For a variety of reasons (direct and indirect), TNOs are believed related to comets which are generally quite dark. The conventional wisdom was an initial best estimate of 0.04 for the albedo of TNOs.

Accumulated measurements of size and albedo now suggest that, while some TNOs are indeed this dark, some are significantly brighter. Reported measurements are summarized below.

The above graph shows albedo vs. diameter for trans-Neptunian objects and centaurs for which diameters/albedos have been measured. Pluto and Charon are also included. Red points indicate TNOs and blue points indicate centaurs.

Most size determinations have been made by comparing thermal and visual observations. Some have been derived for binary TNOs by combining observed brightness, orbital dynamics, and reasonable assumed values of density. A few diameter measurements come from direct imaging or stellar occultations.

Approximate average albedos are as follows (with number of objects in parentheses):

The relevant diameter measurements are listed below. This includes 38 TNOs (of which 6 are binary) and 17 centaurs. The TNOs include the "dwarf" planets Pluto and Eris, and Pluto's satellite Charon is listed as well (for Pluto and Charon, representative measurements are given). All other diameter estimates on the pages Trans-Neptunian objects and List of known trans-Neptunian objects assume an albedo of 0.09. This is a revision in 2005 from a previous model (the old model assumed albedos of 0.09 for Centaurs, 0.04 for TNOs less than 660 km in diameter, and an increasing albedo for larger TNOs based on a best fit to observations through early 2004).

The number of listed objects on this page has increased about 50% over the 2006 version, due primarily to new results from the Spitzer Space Telescope. The average albedos for centaurs and smaller TNOs is relatively unchanged. Two noteworthy trends:

Measured diameters:

designation#/nametypeH mag.diameter (km)albedomethodsource
(134340) Plutodwarf planet,
plutino (multiple)
-0.72302±12
2320±23
2328±46
<2408
2322
0.44-0.61 (B)
0.6 (V)
--
--
--
eclipses
imaging
eclipses
occultation
combined
Tholen, Buie (1990)
Albrecht et ali (1994)
Young, Binzel (1994)
Agner, Elliot (1996)
Young, Young, Buie (2007)
Charonsatellite[0.9]1186±26
>1203
1285±26
1242±41
1212±3
0.378±0.015 (B)
--
0.285±0.015 (V)
--
--
eclipses
occultation
imaging
eclipses
occultation
Tholen, Buie (1990)
Elliot, Young (1991)
Albrecht et ali (1994)
Young, Binzel (1994)
Person et ali (2006 link)
2003 UB313(136199) Erisdwarf planet,
SDO (binary)
-1.2<3310
3000±400
2400±100
2600±400/200
>0.44
0.60±0.15
0.86±0.07
0.70±0.15/0.20
thermal
thermal
imaging
thermal
Brown et ali (2006)
Bertoldi et ali (2006)
Brown et ali (2006)
Stansberry et ali (2008)
 
1977 HZ(2060) Chironcentaur6.5182±8
168±20
180±13
160±20
148±8
142±10
233±15/14
0.14±0.06/0.03
0.13±0.04/0.03
0.148±0.022
0.14±0.02
0.17±0.02
0.11±0.02
0.076±0.010/0.009
thermal
thermal
occultation
thermal
thermal
thermal
thermal
Campins et ali (1994)
Altenhoff, Stumpff (1995)
Bus et ali (1996)
Groussin, Peschke, Lamy (2000)
Fernandez, Jewitt, Sheppard (2002)
Groussin, Lamy, Jorda (2004)
Stansberry et ali (2008)
1992 AD(5145) Pholuscentaur7.0189±26
185±16
140±40
0.044±0.013
0.043±0.020
0.080±0.070/0.030
thermal
thermal
thermal
Davies et ali (1993)
Davies, Tholen, Ballantyne (1996)
Stansberry et ali (2008)
1993 HA2(7066) Nessuscentaur9.660±160.065±0.053/0.023thermal Stansberry et ali (2008)
1995 GO(8405) Asboluscentaur9.066±4
78±8
84±8
0.12±0.03
0.095±0.015
0.055±0.013/0.009
thermal
thermal
thermal
Fernandez, Jewitt, Sheppard (2002)
Stansberry et ali (2005)
Stansberry et ali (2008)
1997 CU26(10199) Chariklocentaur6.4302±30
273±19
236±12
225±25
259±10
0.045±0.010
0.055±0.008
0.07±0.01
0.10±0.02
0.0573±0.0049/0.0042
thermal
thermal
thermal
thermal
thermal
Jewitt, Kalas (1998)
Altenhoff, Menten, Bertoldi (2001)
Groussin, Lamy, Jorda (2004)
Stansberry et ali (2005)
Stansberry et ali (2008)
1995 DW2(10370) Hylonomecentaur8.070±40/200.062±0.050/0.030thermal Stansberry et ali (2008)
1999 TZ1(12929)centaur (near Jupiter)9.3[62]0.085thermal Moullet et ali (2007)
1993 SC(15789)plutino6.9328±58/66
398±108/171
0.022±0.013/0.006
0.035±0.016/0.013 (R)
thermal
thermal
Thomas et ali (2000)
Grundy, Noll, Stephens (2005)
1996 TL66(15874)SDO5.4632±84/98
<958
575±116/115
0.030±0.012/0.007
>0.018 (R)
0.035±0.020/0.011
thermal
thermal
thermal
Thomas et ali (2000)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2008)
1996 TP66(15875)plutino6.8350±50
160±45
0.03±0.01
0.074±0.070/0.030
thermal
thermal
Stansberry et ali (2005)
Stansberry et ali (2008)
1996 TO66(19308)cubewano4.5<897
<902
>0.04
>0.033 (R)
thermal
thermal
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
1998 WH24(19521) Chaoscubewano4.9<742
<747
>0.04
>0.058 (R)
thermal
thermal
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
2000 WR106(20000) Varunacubewano3.7900±129/145
1060±180/220
936±238/324
600±150
500±100
0.07±0.03/0.02 (R)
0.038±0.022/0.010
0.049±0.011/0.014 (R)
0.21±0.09
0.16±0.10/0.08
thermal
thermal
thermal
thermal
thermal
Jewitt, Aussel, Evans (2001)
Lellouch et ali (2002)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2005)
Stansberry et ali (2008)
1995 SM55(24835)cubewano4.8<701
<704
>0.04
>0.067 (R)
thermal
thermal
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
1998 SM165(26308)cubewano, 1:2 res. (binary)5.8238±54*
280±30/29
0.14±0.06 (R)
0.063±0.015/0.012
dynamical
thermal
Grundy, Noll, Stephens (2005)
Stansberry et ali (2008)
1999 DE9(26375)SDO4.7461±46/450.0685±0.0158/0.0119thermal Stansberry et ali (2008)
2001 KX76(28978) Ixionplutino3.21055±165
<804
<822
475±75
650±260/220
0.09
>0.15
>0.148 (R)
0.375±0.125
0.12±0.14/0.06
thermal
thermal
thermal
thermal
thermal
Bertoldi et ali (2002 link)*
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2005)
Stansberry et ali (2008)
1999 TD10(29981)SDO8.890±15
104±14
0.075±0.025
0.044±0.014/0.010
thermal
thermal
Stansberry et ali (2005)
Stansberry et ali (2008)
1999 UG5(31824) Elatuscentaur10.147±2
30±8
[0.07]
0.10±0.04/0.03
photometric
thermal
Peixinho et ali (2001)
Stansberry et ali (2008)
2001 PT13(32532) Thereuscentaur9.080±5
88±9
0.098±0.012
0.043±0.011/0.008
thermal
thermal
Stansberry et ali (2005)
Stansberry et ali (2008)
1998 SN165(35671)TNO5.8460±60/800.043±0.018/0.012thermal Stansberry et ali (2008)
2000 EB173(38628) Huyaplutino4.7<540
<548
480±50
533±25/24
>0.08
>0.084 (R)
0.11±0.02
0.0504±0.0050/0.0041
thermal
thermal
thermal
thermal
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2005)
Stansberry et ali (2008)
2002 CR46(42355) TyphonSDO7.2155±15
175±17/20
0.10±0.02
0.051±0.013/0.009
thermal
thermal
Stansberry et ali (2005)
Stansberry et ali (2008)
1999 TC36(47171)plutino (binary)4.9675±100#
609±93/47#
301±68*
375±50#
405±65/55#
415±39/38#
0.035
0.05±0.01
0.22±0.01 (R)
0.15±0.04
0.079±0.031/0.024
0.072±0.015/0.012
thermal
thermal
dynamical
thermal
thermal
thermal
Bertoldi et ali (2002 link)*
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2005)
Stansberry et ali (2006)
Stansberry et ali (2008)
2000 GN171(47932)plutino6.0321±57/540.057±0.025/0.016thermal Stansberry et ali (2008)
2002 LM60(50000) Quaoarcubewano2.61200±200
1260±190
1260±190
844±207/190
0.12
0.092±0.036/0.023 (R)
0.10±0.03 (R)
0.199±0.132/0.070
thermal
imaging
imaging
thermal
Bertoldi et ali (2002 link)*
Brown, Trujillo (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2008)
1998 SG35(52872) Okyrhoecentaur11.345±5
52±7
0.030±0.005
0.0249±0.0081/0.0055
thermal Stansberry et ali (2005)
Stansberry et ali (2008)
1998 TF35(52975) Cyllaruscentaur9.362±20/180.115±0.090/0.050thermal Stansberry et ali (2008)
2000 QC243(54598) Bienorcentaur7.6175±25
207±30
0.055±0.015
0.0344±0.0127/0.0082
thermal
thermal
Stansberry et ali (2005)
Stansberry et ali (2008)
2002 AW197(55565)cubewano3.3886±115/131
700±50
735±116/108
0.101±0.038/0.022
0.17±0.03
0.118±0.044/0.030
thermal
thermal
thermal
Margot et ali (2002)
Cruikshank et ali (2005)
Stansberry et ali (2008)
2002 GB10(55576) Amycuscentaur7.876±130.180±0.078/0.047thermal Stansberry et ali (2008)
2002 TX300(55636)cubewano3.3<906
<709
<800
>0.085
>0.19 (R)
>0.10
thermal
thermal
thermal
Ortiz et ali (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2008)
2002 UX25(55637)TNO3.6681±116/1140.115±0.051/0.031thermal Stansberry et ali (2008)
1997 CQ29(58534) Logoscubewano (binary)6.680*
77±18*
0.37 (R)
0.39±0.17 (R)
dynamical
dynamical
Noll et ali (2004)
Grundy, Noll, Stephens (2005)
2000 EC98(60558) Echecluscentaur9.570±15
84±15
0.125±0.045
0.038±0.019/0.011
thermal
thermal
Stansberry et ali (2005)
Stansberry et ali (2008)
2001 BL41(63252)centaur11.735±7/80.039±0.025/0.013thermal Stansberry et ali (2008)
2003 FX128(65489) Ceto (binary)6.3109±11/10#
230±19/18#
0.084±0.014/0.021
0.077±0.014/0.011
thermal
thermal
Grundy et ali (2007)
Stansberry et ali (2008)
1999 RZ253(66652) Borasisicubewano (binary)5.9166*
170±39*
0.12±0.01 (B)
0.29±0.12 (R)
dynamical
dynamical
Noll et ali (2004)
Grundy, Noll, Stephens (2005)
2002 PN34(73480)SDO8.2120±100.0425±0.0083/0.0065thermal Stansberry et ali (2008)
2002 GO9(83982) Crantorcentaur9.160±15/130.11±0.07/0.04thermal Stansberry et ali (2008)
2002 TC302(84522)SDO, 2:5 resonance3.9<1195
<1211
1150±337/325
>0.04
>0.051 (R)
0.031±0.029/0.012
thermal
thermal
thermal
Altenhoff, Bertoldi, Menten (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2008)
2001 QT297(88611) Teharonhiawakocubewano (binary)5.588±10*
168±38*
[290#]
0.115±0.025
0.10±0.04
0.13
dynamical
dynamical
dynamical
Osip, Kern, Elliot (2003)
Grundy, Noll, Stephens (2005)
Kern, Elliot (2006)
2003 VB12(90377) SednaOort cloud object1.61700
<1800
<1600
>0.20
0.046 (R)
>0.16
thermal
imaging
thermal
Brown, Trujillo, Rabinowitz (2004)
Grundy, Noll, Stephens (2005)
Stansberry et ali (2008)
2004 DW(90482) Orcusplutino2.3946±74/720.197±0.034/0.028thermal Stansberry et ali (2008)
2004 GV9(90568)cubewano4.0677±71/690.081±0.019/0.015thermal Stansberry et ali (2008)
2003 CO1(120061)centaur8.977±80.057±0.015/0.011thermal Stansberry et ali (2008)
2003 EL61(136108) Haumeaother TNO (triple)0.21380±56
1150±250/100
0.663±0.063
0.84±0.10/0.20
lightcurve/dyn.
thermal
Rabinowitz et ali (2005)
Stansberry et ali (2008)
2005 FY9(136472) MakemakeSDO-0.31500±400/2000.8±0.1/0.2thermal Stansberry et ali (2008)
1998 WW31 and
S/2000 (1998 WW31) 1
cubewano (binary)6.1129±19/9*
152±35*
0.071±0.015/0.017
0.060±0.026
dynamical
dynamical
Veillet et ali (2002)
Grundy, Noll, Stephens (2005)
2001 QC298cubewano (binary)6.1244±55*0.025±0.011 (R)dynamical Grundy, Noll, Stephens (2005)
2002 MS4cubewano3.7726±1230.084±0.038/0.023thermal Stansberry et ali (2008)
2003 AZ84plutino3.9686±99/960.123±0.043/0.029thermal Stansberry et ali (2008)
2003 QY90cubewano (binary)6.3[201#]0.13±0.09dynamical Kern, Elliot (2006)

Notes: For binary TNOs, diameter figures with * are for primary only; diameter figures with # are effective combined diameter for both components. Some reported albedos are for red (R), blue (B), or visible/yellow (V) filters; if unspecified, albedo is geometric visual albedo (or is unspecified by source). Some figures by Grundy, Noll, Stephens (2005) are reanalyses of previous results. Figures in brackets are my estimates based on tabulated data. For sources with *, data is from preliminary unpublished results and may have been superceded.

Methods include: eclipses (analysis of mutual eclipses and occultations of primary and secondary), imaging (direct imaging of disk), occultation (stellar occultation), thermal (thermal infrared or radiometric combined with visual photometry), photometric (derived from modeled spectral photometry), dynamical (fit based on observed brightness, dynamics of primary and secondary, and assumed density), and lightcurve/dynamical (fit based on observed lightcurve, derived rotational properties, and dynamics of primary and secondary).

For more information see:

  • The 1000 km Scale KBOs,
  • Beyond Pluto,
  • Distant EKOs: The Kuiper Belt Electronic Newsletter,
  • Frequently Asked Questions about Quaoar,
  • Diverse albedos of small trans-neptunian objects.


    © 2002-2006, 2008 by Wm. Robert Johnston.
    Last modified 17 September 2008.
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