Wednesday, February 18, 2009

Final thought on 1/31 (for now, at least)

Based on all of the data sets and their now pretty good reductions, I have to conclude that we didn't definitively detect the 2009 1/31 event. I would put eyeball limits of ~1% on what would have been a believable detection.

Why no detection?
  • There could have been no event. Examination of the event movie now posted shows that if Namaka's track shifts just a little to the left no event occurs. Or if Haumea is just a bit smaller along on short axis. Either of these is well within the realm of possibilities.
  • The event was too small. Even the nominal prediction was for only a 0.5% event, which is much smaller than we originally thought. The smaller prediction is because of the mixup between inferior and superior events. Had Namaka gone into eclipse, it would have disappeared at the ~1.5% level. Instead, Namaka shadows Haumea, but it only shadows an already severely limb-darkened part of the disk, so only a 0.5% event.
  • The event occurred when no one was watching. I think this scenario is unlikely. With telescopes from New Mexico to Hawaii we did a very nice job of watching the full range of expected event times.

What's next?
  • The 2/18 event (today from Asia) and the 3/09 event (north and south America) are nearly identical to the 1/31 event, arguing that detections will again be hard. By 3/09, however, Haumea will be up for almost the entire night, allowing beautiful full comparison light curves, which might help detect marginal events.
  • The 3/19 eclipse graze is predicted to miss. I don't know of any plans to observe it.
  • The 3/27 transit (Hawaii) could still be shallow, but the full-night light curves will be beautiful for comparison.
  • 4/14 (Asia) starts the best events, as Namaka begins to transit more deeply across Haumea.
  • 4/25 (America) may or may not occur, but, since this is an eclipse, its depth will be significant if it does. And it will tell us much about the dimensions of the rotation axis.
  • 5/03 (America). Almost certainly a very nice event!
  • 5/13 (Eastern Asia). A deeper occultation; should be 1.5%
  • 5/21 (Eastern Asia). An extremely nice transit. Both Namaka and its shadow will almost certainly cross Haumea, leading to a ~3% event with interesting sub-structure.
  • 5/31 (Western Europe/Africa). A deep occultation, 1.5%, but Haumea is now up only part of the night.
  • 6/08; Starting around here the events are long enough and the nights are short enough that no observatory will be able to see the full event. But the events will be deep, so they will perhaps be better recognizable by then. Deep transit.
  • 6/19; deep occultation
  • 6/26; deep transit. hard to observe well.

My conclusion, from staring at all of these, is that April/May will be the best and that, after the fact, we might be able to go back to some of the earlier events and recognize what might have been real events. Stay tuned......

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