[BAA 00430] OCCULTATION OF A BRIGHT STAR BY JUPITER AUG 3/4

[Rick]

BAA electronic bulletin No. 00430 -- http://www.britastro.org/
Bulletin transmitted on  Sun Aug 2 19:19:04 BST 2009
(c) 2009 British Astronomical Association

Jupiter will occult the bright star 45 Cap (HIP 107302) on the night of 2009 August 03/04 (Mon/Tues).  The star is visual magnitude 6.0 and, for European observers, will be the brightest star to be occulted by Jupiter for the next 100 years.

For UK observers, the occultation disappearance will occur at around 2258 UT (2358 BST), and the reappearance at around 0051 UT (0151 BST). Both events occur against Jupiter's southern limb.  Jupiter's elevation/azimuth at these times will be around +16º/148º, and +22º/176º respectively (based on central UK).  The predicted times are based on the star's reaching the 1 bar level in Jupiter's atmosphere.  However, the star will start varying in brightness as it passes behind the upper levels of Jupiter's atmosphere before the above disappearance time and after the reappearance time.  To make up for this and varying positions within the UK, observers should be ready to observe these events for at least a few minutes before and after the predicted times.  The 96% sunlit moon will be 34º away.

Unfortunately, owing to the large magnitude contrast between the star and Jupiter ( mag -2.8 ), *visual* observers are unlikely to be able to detect the actual moments of occultation or any 'scintillation' through Jupiter's atmosphere; the star will just be seen disappearing into the glare.  Limb darkening on the disappearance (W) side may help counteract this slightly.  Also, since the star is of spectral type A7 ('bluish'), a blue filter may help.

However, any observer possessing a narrow-band 'methane band' filter will be in luck as these were designed specifically for events like this.  A batch of these filters (central wavelength 891nm, FWHM 17nm, 80% transmission) was recently obtained by the International Occultation Timing Association (IOTA).  Weather permitting, occultation observers across Europe will be using these filters and hoping to video record and accurately time the events.  Good quality light curves from these recordings can help to improve the knowledge about Jupiter's atmosphere.

For more detailed information, please click through the following link and its subsidiary links:-

http://www.iota-es.de/jupiter2009/jupiteroccultation.html

Apologies if this e-bulletin arrives at short notice, or too late. The writer is just emerging from the severe side-effects of the China (Eclipse) Syndrome!

Clear Skies,

Andrew Elliott

Assistant Director (Occultations)
Asteroids and Remote Planets Section