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The Pluto and Charon stellar occultations of 22/23 June 2008

Last update: 03 June 2008
What will happen?

On 22 June 2008 near ~ 19:10 UT (night 22/23 June 2008 UT), Pluto will occult a star, as seen from S. Australia and Antarctica. Nine minutes later or so, the same star will be occulted by Charon, as seen from N. Australia, Indian Ocean and southern Africa.

The star position has been measured by Raoul Behrend (Observatoire de Genève), from data taken at the Swiss 1.2m telescope at La Silla, Chile in August 2007:

r.a.= 17h 58mn 33.0152 sec
dec.= -17d 02' 38.360" (ICRF J2000 using the UCAC2 star catalog)

Data taken at the 2.2m telescope at La Silla in September 2007 provides the following position (Dario N. da Silva et al., Observatório Nacional, Rio de Janeiro):

r.a.= 17h 58mn 33.0133 sec
dec.= -17d 02' 38.358" (ICRF J2000 using the UCAC2 star catalog)

Recent (23-27 May 2008) observations made at Pico dos Dias with a 0.6m-telescope provides both the star position and Pluto offset with respect to DE413 ephemeris (Roberto Vieira Martins, Marcelo Assafin et al., Observatório Nacional, Rio de Janeiro and Univ. Federal Rio de Janeiro):

r.a.= 17h 58mn 33.0138 sec +/- 10 mas
dec.= -17d 02' 38.349" +/- 9 mas (ICRF J2000 using the UCAC2 star catalog)

and Pluto's offset wrt DE413:

(O-C) r.a.= -56 +/- 29 mas
(O-C) dec.= +82 +/- 37 mas

The shadow tracks corresponding to the latter measurements are:

Click on images for enhancement

Blue is for Charon's shadow and red is for Pluto. Shadows move from right to left. Dots on centerlines are plotted every mn. Larger dots are for geocentric closest approaches, namely 19:10:24 UT for Pluto and 19:19:01 UT (June 22) for Charon. Assumed half-light level for Pluto is 1223 km (solid lines) and 1% drop level is 1557 km (dotted lines). Assumed radius for Charon is 604 km.

Nominal uncertainty in timing is 30 sec. The uncertainty in NS direction is ~35 mas, or 800 km.

NB. Independent predictions are given on the MIT page

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