Occultation by TNO of a 9th mag star...

[Rick]

From the latest BAA electronic circular...

Extract from message originally sent by J. Lecacheux

On Oct. 25-26 around 1:26 UT (i.e. next Saturday morning) the large TNO #15874 (still unnamed), alias 1996TL66, will pass very close to the magn. 8.7 star HIP 13530, alias SAO 93172. Owing to large ephemeris uncertainties, occultation could occur from any place in Africa, Europe, s.America and a large part of n.America.

(2000) coordinates are R.A. 2h 54m 15s.20, Dec.  +13o 19' 51".3, in a field of Aries easy to find with binoculars.

Details and maps from WinOccult are at the address http://www.bitnik.com/mp/images/TL66.gif

Note that time uncertainty is several minutes, so the target star should be monitored from 1:15 to 1:35 UT.

Risk of missing the Earth is strong, so austral regions, s.Africa leading, will have a better chance than Europe.

According to the Minor Planet Center the absolute magnitude of this TNO is +5.4 .If its albedo is 0.16, a standard value for classical asteroids, then the diameter is 275 km and the occultation of next Saturday might dure 12 seconds, as it is stated in the above mentioned web page. But if albedo is 0.04 only, a more realistic value for cometary nuclei (we suppose), then the diameter is 550 km, and any diametral occultation should be 24 seconds long.

So taking in account projection cosinus, occultation path wider than 600 km is plausible,... if any occultation happens, of course.