[BAA 00210] Occultation of TYC 4974-01069-1 by asteroid 121

[Rick]

Occultation of TYC 4974-01069-1 by asteroid 121, Hermione

On 2005 Dec 12 some time between 06:06 and 06:11 UT, the 209 km diameter asteroid (121) Hermione will occult a 10.2 mag star, TYC 4974-01069-1, in the constellation Virgo for observers along a path across Germany, France, UK. Detailed information on this, and other predictions, can be found at http://asteroidoccultation.com/

Reports should be sent to Gilles Regheere at "gillesregheere at yahoo dot fr" and copied to Roger Dymock at "roger dot dymock at ntlworld dot com" A reporting form is available from the European Asteroidal Occultation Network (EAON) at http://astrosurf.com/eaon/  

In the case of an occultation, the combined light of the asteroid and the star will drop by 4.0 mag to 14.2 mag (the magnitude of the asteroid) for at most 6.5 seconds.

This information is provided by IOTA-ES and based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Ron Stone, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: UCAC.

Further details (from Planoccult email);

(121) HERMIONE  is a very  STRANGE  asteroid. A satellite ~20km in diameter circulate on an orbit with a radius about 790km from the main body.

The main body is  BILOBATED  (or peanut shaped, or snowman shaped) : two lobes of radius 60 and 50 km separated by 120 km and perhaps linked by a bridge of matter 80 km wide, or two connected components of radius 90 and 60 km (a 'snowman' shape) separated by a center-to-center distance of 115 km. (IAU Circular # 8264).  HOWEVER  the position of the "peanut" and its aspect are  UNKNOWN . So it is  VERY  IMPORTANT  to try to observe this occultation!

On the other hand, the position of the satellite is much better known. But taking into account all the uncertainties,  IT  IS  WISE  for any observer in south-west France and even in the very north-east Spain to attempt to OBSERVE  the blink generated by the satellite (IMCCE is still working to upgrade this prediction). Unfortunately, the shadow will run very fast : more than 32.1km/s ! So the occultation by the main body will last no more than 6.5seconds, or maybe 1.5 sec (if it is caused by a small 60km lobe). The satellite will generate a blink about a 1/2 second only, it could be almost a 1/2 minute  BEFORE  OR AFTER  the predicted time for the main body. Videocording or better fast driftscan is prefered to visual.  BUT  be sure of good timing !

YOUR  OBSERVATION  CAN  BE  OF  HIGH  SCIENTIFIC  IMPORTANCE. Good luck to everybody. Credits to IMCCE (Berthier, Hestroffer & al.) and Marchis & al. (Univ. of Cal.)

Regards

Roger Dymock

Director Asteroids and Remote Planets Section, British Astronomical Association  
BAA ARPS website; http://homepage.ntlworld.com/roger.dymock/index.htm

[Rick]

A reminder to observe this occultation if you possibly can.

Should be a very interesting event as the asteroid itself is peanut shaped and it has a satellite.

Full details of this and other occultations occurring this month may be found at http://astrosurf.com/eaon/Occultations%20Dec.htm

Regards

Roger Dymock

Director Asteroids and Remote Planets Section, British Astronomical Association  
MPC Observatory Code 940
BAA ARPS website; http://homepage.ntlworld.com/roger.dymock/index.htm