Help us find asteroid 146 Lucina's satellite late Wednesday night (actually Thursday morning), September 19–20!
1982, an occultation (eclipse of a star) by a probable satellite of
this asteroid was video recorded with the 1-meter telescope at Meudon
Observatory near Paris. The occultation by Lucina itself was
observed in a different path crossing northern Spain. The
observation implies an object at least 6 kilometers across about 1,600 km
from Lucina, as reported in Icarus, Vol. 61, pp. 224-231.
Observers across most of the western and central USA, northern Mexico, and
Canada west of Quebec have a chance to make confirmatory observations of the satellite if they monitor the easily found 7.9-magnitude star SAO 78252, which is only 0.7° south of 3rd-magnitude μ Geminorum (Tejat). This event is expected early Thursday morning, September 20th, at around 3:48 am PDT, 4:49 am MDT, 5:50 am CDT,
or 6:50 am EDT, depending on your location and time zone.
Especially those with video
equipment in most of western North America are encouraged to record the star
for a possible quick blink, expected to last about 0.3 second, that
could be caused by the satellite. In addition, observers in
northern California, northern Nevada, southern Idaho, the northernmost part of Utah,
northern Wyoming, southeast Montana, northwest South Dakota, southern and eastern North
Dakota, northern Minnesota, and western Ontario will have a spectacular occultation by Lucina that will last
almost 7 seconds; visual, video, and CCD observers throughout those
areas are especially encouraged to observe to help us determine the
size and shape of Lucina.
Lucina, a C-class ("carbonaceous")
asteroid, is expected to be about 132 km across. This is the best asteroidal occultation in North America during the rest of this year, and it's even better than the August 21st event that also involved Lucina. Two observers in New Mexico and one in Arizona timed the August 21st occultation; several others, including me, had no occultation (clouds prevented me from getting deeper into the predicted path). Results are on the August 21st Lucina line here.
For more detailed information and instructions for reporting your observations, see my website:
David W. Dunham
Sky & Telescope