Occultations by Pluto

(mainly 20 July 2002,
but also 01 July 2002 and 09 August 2002)

Click here for the: latest updates for the July 20, 2002 event !!!

This page gives the circumstances (maps, finding charts, etc...) of three occultations by Pluto predicted by S.W. McDonald and J.L. Elliot, see Astronomical Journal 119 , 1999-2007, April 2000 and 120 , 1599-1602, September 2000.

These occultations occur on 01 July 2002, 20 July 2002 and 09 August 2002. The occulted stars on each date are respectively referred to as P/C 119, P/C 126 and P/C 130 by McDonald and Elliot.

The most interesting event occurs on 20 July 2002. However, and for information, some maps and comments are also given for the less promizing events of 01 July 2002 and 09 August 2002, see the end of this page.

To have more information on the general context and the scientific goals of these observations,

click here: why observing a Pluto occultation?

Salt, sand, snow and sky. The picture below shows the "Moon Valley" in the desert of Atacama, near the triple point between Bolivia, Chile and Argentina. The mountains in the horizon culminate at 5500-6000 m, and mark the border with Bolivia. The central flash for the Pluto occultation of July 20, 2002 could be visible from this region, see below.

(photo B. Sicardy).

20 July 2002, star P/C 126

ATTENTION: the predictions for 20 July 2002 have changed (as of May 22, 2002): see the new map below!

The star is double!

After observations by Ron Stone, it appears that P126 is double. The angular separation is about 2.2 arcsec, with magnitudes R= 12.33 ("P126a") and R= 12.95 ("P126b"), see the analysis by Mike Person and Jim Elliot in the MIT site. The prediction below are for the brighter component (P126a) of the pair. The other component, P126b, yields occultation tracks of Pluto and Charon outside the Earth.

Note that there are little changes compared to the previous predictions posted on this site on April 24, 2002.

The adopted position for P126a is now (J2000):

RA = 17 00 18.0199
DEC=-12 41 41.995

This prediction assumes furthermore a (O-C) of Pluton:

D_RA * cos(delta) = -0.04 arcsec
D_DEC = -0.04 arcsec

with respect to the JPL Horizons ephemeris of Pluto/Charon (PLU006 + DE405).

Predictions for 20 July 2002: South America

The shadow of Pluto (grey region) goes from right to left. The central line is drawn with dots giving the position of the shadow center every minute. A reference time (01:45 UT) is given in the figure. The outer dotted lines encompass the region where Pluto's atmosphere will cause a drop of signal of a few percents or larger.

Position of Charon 17-23 July 2002

The diagram above shows the position of Charon with respect to Pluton during one revolution, between 17 July 2002 and 23 July 2002 (Charon orbital period is about 6.387 days). Each square marks Charon's position at 00h UT. The sizes of Pluton and Charon on the sky are respected in this diagram.

The finding chart P/C 126 is provided below, with the star at the center and a field of 8.5 x 8.5 arcmin around. The brighter star in the upper right corner is a Tycho star identified by the numbers TYC1 5651, TYC2 1568 and TYC3 1 in the Tycho main catalog (see the Vizier site ).

These maps can be generated online on the skyview gsfc NASA site.

The star is very red!

The maps below show details of the upper right corner of the finding chart, in the three bands J, H and K (see the Gator site at Cal'Tech). In these charts P/C 126 is the brightest object at the lower left corner.

Note how the star becomes brighter than the Tycho star at longer wavelengths. The Gator site provides the following magnitudes for P/C 126:

B= 13.8
R= 11.6
J= 9.76
H= 8.83
K= 8.53

It is a very red star indeed, probably a M class.

You may visit Mark Buie's site to find more information on the finding chart around P126 (see below), as well the photometry and the position of the star, plus other neighbor stars.

More about the Atacama region,
the region of the central flash

The Licancabur Volcano (5930 m) from San Pedro de Atacama, Chile. From the top of the volcano: the crater taken from the Bolivian side and the stormy weather... (April 2001)

Photos B. Sicardy

01 July 2002, star P/C 119

Predictions for 01 July 2002 and chart for P/C 119

On 01 July 2002, P/C 119, V(CCD)= 11.4 : The Earth essentially goes between the shadow of P and C. I doubt that any material between Pluto and Charon could cause any dimming of the star.

09 August 2002, star P/C 130

Predictions for 09 August 2002 and chart for P/C 130

On 09 August 2002, P 130.1, V(CCD)= 14 : quite a faint star. Charon's shadow is too far south to hit the Earth and is not visible in this diagram.

About the background image: with Thierry near the top of Illimani (6430m), Bolivia, 26 August 1997 at sunrise.

Photo B. Sicardy