The surface of Pluto-twin The surface of Pluto-twin TNOs 2005 FYTNOs 2005 FY99 and 2003 and 2003

UBUB313313Javier Licandro(1,2), N. Pinilla-Alonso(3), M. Pedani(3), E. Oliva(3), P. Leisy(1), G.P. Tozzi(4) and W. Grundy(5)

(1)Isaac Newton Group of Telescopes(2)Instituto de Astrofísica de Canarias(3)Fundación Galileo Galilei(4)INAF-Oss di Arcetri(5)Lowel Observatory

Pluto’s spectrumPluto’s spectrum

• deep CH4 ice bands, shifted by about 15A respect to laboratory.

• weak N2 (2.15 microns) and CO (1.58, 2.35 microns)

• no deep water ice or CO2

• red in the visible organics (tholins, irradiated CH4)?

2005 FY2005 FY99

Licandro et al. 2006

Observed simultaneously with the TNG and WHT at La Palma on Aug. 1st, 2005.

Deep CH4 ice bands, some of

them not seen in Pluto’s

spectrum ( e.g. 0.63 microns)

Red colour in the visible,

similar to Pluto

2003 UB2003 UB313313

Licandro et al. 2006

Brown et al. 2005

Near infrared spectrum of

2003 UB313 similar to our 2005

FY9 spectrum

2003 UB2003 UB313313

Licandro et al. 2006, in preparation

•Observed with the WHT on Oct. 20th, 2005.

COLOURS COLOURS

Licandro et al. 2006, in preparation

All present slightly red slope

in the visible

S’ measured using the 0.59

and 0.825 microns

reflectance

S’(UB313)= 4 %/1000A

S’(FY9)= 8.9 %/1000A

S’(Pluto)= 8.9 %/1000A

Posible organics in the

surface, probably irradiated

methane (Brunetto et al. this

meeting). Less abuntant in

2003 UB313

Band depths Band depths

Licandro et al. 2006, in preparation

FY9/Pluto (0.73) = 6

FY9/Pluto (0.89) = 3

FY9/UB313 (0.73)= 1.9

FY9/UB313 (0.89)= 1.1

Indicative of abundance and/or grain sizes

Band depths Band depths

•In the infrared the differences

are smaller but consistent, •light reflected from the 3 objects

samples different mean optical

pathlengths

•Saturation of deeper bands

Different concentration of

CH4 and or thickness of

the CH4 layers

Band depths and Band depths and saturation effectssaturation effects

In the infrared the

bands are highly

saturated visible

spectral range is

very important

Weaker bands

sample deeper

layers

Band shifts: 2005 FY9 Band shifts: 2005 FY9

Licandro et al. 2005

Band shifts respect to laboratory pure CH4 ones

indicative of dilusion in N2

Shifts < 5 A

high concetration

of CH4 or no N2 on

2005 FY9 surface

Atmosphere?

Crucial to

determine if there

is some N2

SHIFTED ?

Band shifts: 2003 UBBand shifts: 2003 UB313313

Band shifts: 0.73 micron Band shifts: 0.73 micron bandband

PlutoCH4 (0.05cm)

2005 FY9CH4 (4.5cm)

2003 UB313CH4 (1.5cm)

Band shifts: 0.89 micron Band shifts: 0.89 micron bandsbands

PlutoCH4 (0.05cm)

2005 FY9CH4 (4.5cm)

2003 UB313CH4 (1.5cm)

Problems with wl calibration? NO!!!! NO!!!! Uncertainties on Sky lines < 1A Uncertainties on Sky lines < 1A

2003 UB313 shifted by 15 A

CH4 (1.5cm)

Band shifts: 2003 UBBand shifts: 2003 UB313313

Narower?

Band shifts: 2003 UBBand shifts: 2003 UB313313

There is CH4 diluted in N2 ice in

the surface of 2003 UB313

Weaker bands sample deeper

layers evidence of a vertical

compositional gradient ?

Colapse of the atmosphere?

CharonsCharons

Band shiftsBand shifts

Band shiftsBand shifts

Band shiftsBand shifts

La atmósfera de Plutón La atmósfera de Plutón

atmósfera de CH4, N2 y CO

Condiciones suficientes de tamaño, masa, y temperatura

La atmósfera de La atmósfera de Caronte?Caronte?

No se ha detectado

La superficie de Plutón La superficie de Plutón

• bandas desplazadas

metano diluido en

N2

• inhomogeneidades

superficiales

relacionadas con

diferente composición

y albedo

Observations Observations

Visible

4.2 William Herschel TelescopeISIS

Infrarred3.6 m Telescopio Nazionale GalileoNICS

Los TNOs grandesLos TNOs grandes

Diferent composition or Diferent composition or diferent surface diferent surface

evolution?evolution?