Bruno SicardyObs. Paris - LESIA

and occcultation Team

Bruno SicardyObs. Paris - LESIA

and occcultation Team

PHYSIQUE DE L'ATMOSPHÈRE DE PLUTON ET TAILLE DE CHARON DÉDUITES

D'OCCULTATIONS STELLAIRES 2002-2006

PHYSIQUE DE L'ATMOSPHÈRE DE PLUTON ET TAILLE DE CHARON DÉDUITES

D'OCCULTATIONS STELLAIRES 2002-2006

François ColasFrançois ColasThomas WidemannThomas Widemann

Atelier 3ème zone, Nantes 11-12 janvier 2007

Atelier 3ème zone, Nantes 11-12 janvier 2007

special moment: equinox in 1988, perihelium in 1989 (period 248 years) effects on N2 pressure-equilibirum atmosphere?

Charon's size? ( density ?)

Charon's surface gravity ~ 1/2 Pluto's gravity possibility of atmosphere?

Pluto and Charonprobed by occultations

C.J Hansen & D.A. Paige Icarus, 120, 247-265 (1996)

complex interplay of large distance variations & drastic seasonal effects

2001

2020

2011

Pluto motion in the sky

Pluton 20 juil. 2002

P131.1 August 21, 2002

spikes: scintillation in Pluto’s atmosphere

temperature contrast:warmer near pole cooler near equator

Sicardy et al. Nature, 10 July 2003

Sicardy et al. Nature, July 2003

Imm. Eme.

Sicardy et al. « Large changes in Pluto’s atmosphere

as revealed by recent stellar occultations »

Nature, 10 July 2003

1988

2002

2006

pressure doubled!

?

Time

rP

B'P

rN

1988

2002

2006

C.J Hansen & D.A. Paige Icarus, 120, 247-265 (1996)

1900 2000 2100

10 bar

1 bar

0.1 bar

Pluto in 1988

Pluto in 2002

measuring Charon

0.89"

2UCAC 26257135(D. Herald, Aug. 2004)

QuickTime™ et undécompresseur Vidéo

sont requis pour visionner cette image.

VLT/NACO K band, Charon occultation 11 July 2005

1"

Pluto

star + Charon

Sicardy et al., Nature 439, 52, 2006« Charon’s size and an upper limiton its atmosphere from a stellaroccultation »

R= 603.61.4 km

56 K - N2100 K - CH4

56 K

Some conclusions:

Atmosphere: limit is model dependent, e.g.

CH4 with inversion layer: psurf < 15 nbar…or…N2 isothermal 56 K: psurf < 110 nbar etc…

Charon’s size: RC = 603.6 1.4 km

Charon’s density: C = 1.65 0.06 g cm-3

(taken from Buie et al. AJ. 132, 290, 2006, NB. P = 2.03 0.06 g cm-3 for Pluto)

Possibility to retrieve Pluto’s radius with accurate Charon’saccurate size --> refine atmospheric model

recent & future stuff…

12 June 2006 Pluto occultation

1988 2002

12 June 2006, Australia

Stockport

Blue Mountains

Hobart

20 cm

40 cm

50 cm

Time (sec UT)

Stockport

Blue Mountains

Hobart

pressure expansion factor since 2002

68.3% c.l.

99.7% c.l.

2

1988 2002

2006

Hansen & Paige, Icarus 120, 247 (1996)

1988

20022006

pressure @ 1215 km(bar)

10

1

5

2

time (year)

New Horizon

2007: four Pluto & co events?

Nix, 22 mars 2007

2.1"

Hydra

Pluto **et** Hydra12 mai 2007

Paranal & La Silla

Pluton14 juin 2007

Paranal, La Silla & SOAR

en cours:

prédictions d'occultations par de gros TNO

Eris, 2005 FY9, 2003 EL6, Sedna, Orcus,Quaoar, Varuna, … (voir présentation T. Widemann)

Paranal Jul 2005

… merci