Occultation of TYC 1396-00214 by Jupiter, 01-07... April 2003
A remarkable occultation by Jupiter has recently been discovered by Alfons Gabel
(Germany). The star TAC +19 02365 = GSC 1396 214 = TYC 1396-00214 is very near the
stationary point of Jupiter which occurs on 4 April 2003.
As a result, there will be extremely slow occultations by Jupiter's atmosphere (four
times), and also by Jupiter's rings and probably, Jupiter's
satellites, between 1 April (no hoax!) and 9 April 2003.
According to Jean Lecacheux, the J2000 coordinates of the star from
the Tycho 2 catalog + proper motion + annual parallax effect is:
08h 42m 42s.4731
+19d 05' 58".880
A survey, also made by Jean, provides the following magnitudes:
B=12.07 (B-V = +0.45 Sun : +0.65)
R=11.02 (V-R = +0.60 ,, : +0.54)
I=10.61 (V-I = +1.01 ,, : +0.88)
J=10.31 (V-J = +1.31 ,, : +1.12)
H=10.02 (V-H = +1.60 ,, : +1.43)
K= 9.89 (V-K = +1.73 ,, : +1.49)
The star will be occulted 4 times by the planet, first in the S. Pole
region and then in the equatorial region. Relative velocities as low as
0.1 km/sec will be achieved at some points. This could yield detailed
scans of gravity waves in Jupiter's stratosphere, at 4 different places.
The atmospheric occultations can be attempted in the methane band at 0.9
microns, or better, in K (2.2 microns). We did observed a stellar occultation by
Jupiter in October 1999 with a K= 9.9 star, and the contrast star/Jupiter's limb
was very good.
The large galilean satellites will probably occult the star from
certain sites, but the contrast will be poor (satellites too bright,
star too faint), and methane bands cannot be used for these icy
The small inner satellites are much more likely to cause usable
occultations as they are much fainter.
An interesting issue is the possible detection of small unknown
satellites, as the small ones presently detected near the main ring
(namely Metis, and Adrastea, with radii ~ 10-20 km) are probably the
tip of a larger population of as-yet unnoticed km-sized or less
The greatest concentation of these small bodies is expected in the
main ring region, between 128000 and 129000 km from the planet center.
Last but not least, the main rings will occult the star. As far as I
know, only one occn was observed to catch Jupiter's rings (on 11
December 1980) with negative detection up to a normal optical depth of
0.008 (Dunham et al., AJ 87 , 1423, 1982).
The April ring occultation has two favourable circumstances with
respect to the event in 1980: (1) slow motion of the star wrt the
rings, resulting in a better signal/noise and (2) almost edge-on view
(elevation= 0.2 deg) of the rings, resulting in an amplification by a
factor of ~ 300 of the normal optical depth of the main ring.
Still, the optical depth of the entire main ring will remain very small, and
thus a detection will be difficult. Rather, one might expect to detect
some large particles (or small satellites) in this ring, as explained above.
If positive, however, a detection of a dusty ring by simultaneous
observations at various wavelengths might help understanding better
the size distribution of the jovian rings.
It is important to note that the star will cross TWICE the ring
orbit. For instance, the close up view for Pic du Midi (see below)
shows that the star will scan for about 10 mn the main ring
region around 23:40 UT April 6, and then again for about 10 mn around
00h25 UT April 7.
You may figure out you own shedule according to the maps below. Thus my
advice is to stay on the star for at least one hour around the nominal
middle time for the all event, or more if possible, in order to
carefully scan the ring region.
It is also important to note that we are looking not only for a faint
absorption during the ring crossing, due to dust, but ALSO and mainly
for brief and deep occns caused by small satellites (or large particles)
embedded in the ring region. Such brief interruptions should be confirmed by
another redundant nearby instrument if possible, as they might arise from bird
passing by, clouds, electronic glitches, etc, etc...
A reference star (or satellite) is important! There is one at 2'04" NNW of
the occulted star, which has about the same V mag, see the field below.
A possibility to save acquisition time is to have two small windows, one on the
occulted star and the other one on the reference star.
In case you cannot reach a photometric reference object (satellite or star)
you may use as a better than nothing backup some benchmark on Jupiter's disk.
According to the diameter and quality of your mirror, the transparency of
the sky, the distance of the star to the planet limb and the sensitivity
of your receptor, you may try various configurations (I band, wide CH4
filter, narrow CH4 filter, mask on Jupiter, etc...) to see what is optimum
General views of the stellar tracks as seen from Pic du Midi (France),
La Palma (Canaries Islands, Spain), La Silla (ESO, Chile), Palomar
(California, USA), Max Valier Observatory (Italy) and New Jersey (USA).
The dots are plotted every hour, the squares are plotted every 24
hours. The continuous curve is the geocentric track.
Detail of the ring occultations as seen from Pic du Midi, La Palma,
La Silla and Palomar:
... and from Max Valier Observatory and New Jersey:
... and from Nyrola Observatory (Finland)
... and from Livermore (CA, USA)
... and more details on the Pic du Midi observational circumstances:
Field of view on April 07, 00h UT, as seen from Pic du Midi:
The Earth seen from the the direction of Jupiter from 06 April 2003 at 23:00 UT to
07 April 2003 at 07:00 UT, at one hour intervals. Note that the times at Jupiter
take into account the light travel time (about 40 mn).
About the background image: the Atacama desert, near the border between Chile and
Bolivia. The volcanoes in the skyline culminate at 5000-5500 m above sea level.
This photo was taken after the Pluto occultation of 20 July 2002 (B. Sicardy).
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