Stellar Occultation by Charon as Observed from Chile

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Stellar Occultation by Charon as Observed from
Chile

• Taavi Tuvikene
• Vrije Universiteit Brussel
• Contact Group Meeting, 19 May 2006

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Cerro Armazones, Chile
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Observatorio Cerro Armazones
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42 cm
84 cm
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Rotating the Dome
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Stellar Occultation by Charon

• Occultation Charon passes in front of a star
• The highest spatial resolution available from the
  Earth
• Stellar occultation in 1980
• 2 years after discovery
• one observation (in South Africa)
• lower limit to Charons radius 600 km
• 25 years later ...

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11 July 2005 (prediction)

• Geocentric mid-time11-7-2005 033701 (UT)
• Shadow diameter1200 km
• Shadow velocity on the ground 21.3 km/s
• C313.2 magnitudeR 14.8
• Distance of Pluto30.06 AU

http//occult.mit.edu/research/occultations/Charon
/C313.2.html
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Observatories / Research Groups
San Pedro

• Massachusetts Institute of Technology (MIT)
  Williams College
• Group led by Paris Observatory
• Southwest Research Institute (SwRI) Wellesley
  College

Paranal
Cerro Armazones
Las Campanas (du Pont, Clay)
Cerro Pachon (Gemini)
Cerro Pachon (SOAR)
El Leoncito
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Telescopes Instrumentsused by MIT team

• Chile
• Observatório Cerro Armazones 84 cm POETS
• Las Campanas
• Du Pont 2.5 m POETS
• Clay 6.5 m POETS
• Cerro Pachón
• Gemini South 8 m Acquisition Camera
  (R-filter)
• Brasil
• Observatório Pico dos Dias, Itajubá 0.6 m
  POETS no observations due to clouds

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Stellar Occultation (video)
http//occult.mit.edu/research/occultations/Charon
/C313.2/C313OccMovie.html
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Light-curves
See Figure 2 in Gulbis, A. A. S. et al. Nature
439, 4851
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Occultation Chords
See Figure 1 in Gulbis, A. A. S. et al. Nature
439, 4851
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Charons Atmospheric Models
See Figure 3 in Gulbis, A. A. S. et al. Nature
439, 4851
Clay light-curve
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Results (Gulbis et al. 2006)

• Charons mean radius 606 8 km
• Bulk density 1.72 0.15 g/cm3
• Rock-ice mass fraction 0.63 0.05
• Smaller than Plutos impact formation scenario
• No significant atmosphere

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Results
Nature, 5 January 2006