N.23 dotto physica-characterization-of-trans-neptunian-objec

Elisabetta Dotto(INAF-Osservatorio Astronomico di Roma)

Physical characterization of Trans-Neptunian Objects and Centaurs

Pisa 14-16 June 2010Elisabetta DottoINAF-Osservatorio Astronomico di RomaWorkshop on Paolo Farinella

Centaurs and TNOsCentaurs and TNOs

Elisabetta DottoINAF-Osservatorio Astronomico di RomaPisa 14-16 June 2010 Workshop on Paolo Farinella

Sedna:(announced on March 15, 2004)

a = 532 AU

q = 76 AU

Q = 988 AU

Extended scattered disk


Centaurs and TNOsCentaurs and TNOs


Centaurs


30 A.U. < ∆ < ? A.U. ~ 1130 TNOs ~ 161 SDOfew 104 with D ≥ 100 km

5 A.U. < ∆ < 30 A.U.95 Centaurs about 107 D ≥ 1 km


06/15/10Antonella BarucciLESIA, Observatoire de Paris

• Rotational period, shape, surface structure • Density (with some assumptions...), 9 estimations (45% literature)

Centaurs and TNOs: light curves & densitiesCentaurs and TNOs: light curves & densities

06/15/10Antonella BarucciLESIA, Observatoire de Paris

Prot

(a/bMAX

= 2.31)[otherwise unstable to rotation]

Density estimation

Haumea (Illustration: Ann Feild/STScI/ESA/NASA)

Jacobi ellipsoids(Chandrasekhar)



Pearson correlation coefficient:

r = -0.46

Probability of no correlation:

~ 4.8%(with 19 objects)

A dimension/density trend? (Sheppard et al. 2008)

(Perna et al. 2009)


-0.29

~ 23%

Pearson correlation coefficient:

r = -0.46

Probability of no correlation:

~ 4.8%(with 19 objects)



(Perna et al. 2009)


increase the statistics

albedo measurements

a new model for densities



(Perna et al. 2009)


Taxonomical classification

(Barucci et al. 2010)


G-mode statistical method according to the Barucci et al. (2005) system

Classic

al ob

jects

(Barucci et al. 2010)Elisabetta DottoINAF-Osservatorio Astronomico di RomaPisa 14-16 June 2010 Workshop on Paolo Farinella

Cold

Hot

Classic

al ob

jects

Hot and Cold Classicals, True Compositional Diversity?

•dynamically cold: red colors, low i, small

•dynamically hot: diverse colors, moderate

and high i, larger sizes

(Barucci et al. 2010)Elisabetta DottoINAF-Osservatorio Astronomico di RomaPisa 14-16 June 2010 Workshop on Paolo Farinella

(Gomes 2003)


Cold = RR = old

Hot = BB = young

(Fornasier et al. 2009)

Slope:

1 < S < 51 %/103 Å

Visible Spectra


kerogene + olivine (+ water ice)

tholins + amorphous carbon(+ water ice + olivine)

Geographical mixtures of :

Synthetic Spectra

• > 50% of objects have H2O ice (amorph+crystalline)

• CH4, CH3OH, C2H6 , N2, NH3………………

• aqueous alteration (2003 AZ84, Chariklo and Typhon)

• surface heterogeneities

V+NIR spectroscopy



Featureless spectra

Irradiation mantle

(Dalle Ore et al. 2009)

50000 Quaoar

24% Triton tholin + 7% amorphous carbon + 10% N2 + 26% CH3OH + 33% CH4 (contaminated by small inclusion of Titan tholin) , albedo= 0.15

90377 Sedna (2003 VB12)

(Barucci et al. 2005)(Emery et al. 2007)


Surface heterogeneity

VLT-ESO


Surface model:H2O+Tritan&Titan Tholins+Serpentine+CH4+N2+CH3OH

90377 Sedna (2003 VB12)

TNO 55638 and on Centaur Pholus:


Methanol


(55638) 2002 VE95

11% CO3OH+11%H2O+26%TrTh+37%TTh+15%Ca

12/2007

11/2008

18%CH3OH+3%H20+40%TrTh+26%TTh+7%K+6%Ca


• > 50% of objects have H2O ice (amorph+crystalline)

• CH4, CH3OH, C2H6 , N2, NH3………………

• aqueous alteration (2003 AZ84, Chariklo and Typhon)

• surface heterogeneities

V+NIR spectroscopy


Origin of the spectral diversity among TNOs

• Resurfacing vs. Irradiation (Luu & Jewitt, 1996)

Formation of an irradiation mantle

Resurfacing

The color of an object depends on its level of resurfacing

Red spectra can be flattened by ion irradiation (Moroz et al. 2002; 2003)


Ion Irradiation of an Organic Sampe:

ASPHALTITE – natural solid complex hydrocarbon material (solid oil bitumen)

Consists of aliphatic and polyciclic aromatic hydrocarbons (PAHs)

Carbon aromaticity (fraction of aromatic C) is 0.33

H/C ratio is 1.4

Density ~1 g/cm3

Soluble in organic solvents (true bitumen)

0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.800.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Asphaltite Dust1 (IN SITU)

Dust1+7,3x1015 H+/cm2 (30 keV)

Dust1+7,3x1015 H+/cm2 (30 keV)

+ 6,6x1015

N+/cm

2 (15 keV)

Dust1+7,3x1015 H+/cm2 (30 keV)

+ 5,9x1016 N+/cm2 (15 keV)

Sca

led

Ref

lect

ance

Wavelength (microns)0.3 0.4 0.5 0.6 0.7 0.8

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Asphaltite "Dust"

Asphaltite "Dust" + 0.5x1015

Ar++

/cm2

Asphaltite "Dust" + 1.5x1015

Ar++

/cm2

Sca

led

Ref

lect

ance

Wavelength (microns)

(Moroz et al. 2002)

Ratio of icy bodies as a function of their taxonomy

• all objects classified as BB were found to have ice on their surfaces

• for other taxonomic classes it seems that a ratio of icy and non-icy bodies is approximately the same


Scott Sheppard (2010) in AJ:« The color of extreme outer solar system objects »

Inner Oort cloud:

(90377) Sedna, 2006 SQ372 & (87269) 2000 OO67

ultra red (S>25)


The reddest objects

RR class objects are present in all dynamical populations

reddest in Centaurs & detached

higher concentration in the classical group (cold=primitive?)

ultra red objects in the inner Oort cloud (characteristic of objects kept far from the Sun?)

Does red mean « primitive »?

Pisa 14-16 June 2010 Workshop on Paolo Farinella Elisabetta DottoINAF-Osservatorio Astronomico di Roma

• The wide difference in surface composition and colour could be connected to different original composition and/or different experienced processes.

• Collisions must have played a fundamental role on the evolution of TNOs including heating and chemical changes. The consequence of collisions is not only the alteration of the surface properties but also the modification of the internal structure. Collisions are relevant for small and large objects (e.g. Charon-Pluto).

Summarizing:

Pisa 14-16 June 2010 Workshop on Paolo Farinella Elisabetta DottoINAF-Osservatorio Astronomico di Roma

N.23 dotto physica-characterization-of-trans-neptunian-objec

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