Last night at about 2:12am EDT
the asteroid Erigone blocked the light of the star Regulus for observers in
parts of the northeast. From the
observer's point of view, Regulus would appear to wink out for a period of up
to 14 seconds. Such an event is called
an occultation.
On the face of it, seeing a star
vanish briefly seems an unlikely thing to get up in the middle of the night
for, but it is true Citizen Science.
With nothing more than a stopwatch* and an accurate clock, we could
contribute to astronomer's knowledge of this asteroid's exact orbit, its size,
and even whether or not it has a satellite--a "moon" of its own. Enough
observers in the right places would allow determination of the size of
Erigone's shadow--which is the size of Erigone itself--while brief occultations
outside of this belt of shadow would likely show the presence of a companion. Even observers in New York City (which was in
the path of the shadow) could contribute, since Regulus is bright enough to be
seen even there.
And consider the idea
itself. Astronomers know the orbit of
Erigone (a 45-mile-wide rock way out in the main asteroid belt between Mars and
Jupiter) well enough to line it up with a hot, powerful young star so far away
(at 79 light years) as to be a mere bright point of light, and locate the
shadow they cast to a region of the earth stretching diagonally across New York
State and bits of Connecticut and Pennsylvania in a time nailed down to a few
minutes. The first prediction of this
occultation was made ten years ago.
This is "pocket
billiards" of a very high order!
Leo, with Regulus the brighest star in the lower right.
http://www.mediapolis.k12.ia.us/middle/middle/Todd%20H/6th%20grade/2008%20students/Jupiter%20AF/space/constellations/constellations.htm
(The disk-like star images are a telescope artifact--by eye, they're all bright but tiny points.)
Alas! --I missed it. After reading up on the event, figuring out
the stop watch function on my wrist watch, and setting my alarm, I looked
outside to find solid overcast. And by
this morning it was raining. Mind you,
eastern Massachusetts is well outside the occultation zone of Erigone itself,
but I cherished the idea of being part of the effort to see if she might possibly
have a satellite. Even if--as was very
likely--I saw nothing at all but Regulus shining steadily out of the
constellation Leo, that would be just as useful: it would tell astronomers one
place where a satellite definitely wasn't. Combined with the simultaneous observations
of hundreds of others, it could have given astronomers a pretty clear idea of
the Erigone "system."
Since this was to have been
"the best and brightest asteroid occultation ever predicted to occur overa populated area," I am a little bummed.
*Even the stopwatch isn't strictly necessary: we are advised that simply counting aloud, "one-cigarette, two-cigarette,..." allows accuracy to about a quarter of a second.
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