KBO encounters |
KBO encounters |
Jun 16 2017, 08:14 PM
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#391
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Senior Member Group: Members Posts: 1582 Joined: 14-October 05 From: Vermont Member No.: 530 |
There is an update about a July 10 occultation over the Pacific that SOFIA will observe.
And a July 17 occultation that crosses Patagonia. https://www.nasa.gov/feature/new-horizons-t...xt-flyby-target That said, info on the June 3 occultation is "stay tuned." |
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Jul 5 2017, 05:25 PM
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#392
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
early results: no occultation detected, MU69 may be smaller than expected
https://www.nasa.gov/feature/new-mysteries-...xt-flyby-target |
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Jul 6 2017, 05:39 AM
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#393
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
I re-read this and maybe I was wrong. what does it mean
QUOTE While MU69 itself eluded direct detection ?I interpreted this as meaning that no occultation was detected, but I am not so sure now. also: QUOTE he fact that we accomplished the occultation observations from every planned observing site but didn’t detect the object itself
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Jul 6 2017, 05:53 AM
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#394
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Senior Member Group: Members Posts: 2079 Joined: 13-February 10 From: Ontario Member No.: 5221 |
They observed the star, but not the occultation, is my interpretation. Future observations like SOFIA next week should tell us more about what's going on here (it can't have vanished!)
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Jul 6 2017, 02:13 PM
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#395
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Member Group: Members Posts: 540 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
Among the possibilities I've read mentioned are that it might have a much brighter surface than everyone has been thinking, and therefore it is smaller. Or it might be a binary object (or triple, or multiple). Maybe both.
Being smaller and/or an orbiting pair would make it more likely to "slip through the cracks". That is, the shadow(s) could pass unseen through the spaces between the observing telescopes with higher probability. |
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Jul 7 2017, 03:23 AM
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#396
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Member Group: Members Posts: 100 Joined: 25-April 08 From: near New York City, NY Member No.: 4103 |
My interpretation is that they did not see the object (not surprising), and I can't tell from the article if they recorded an occultation. Can we get some clarification?
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Jul 7 2017, 05:57 AM
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#397
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Senior Member Group: Members Posts: 2079 Joined: 13-February 10 From: Ontario Member No.: 5221 |
There was no occultation observed, it's pretty unambiguous. Alan can correct me if I'm wrong, of course!
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Jul 7 2017, 11:19 AM
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#398
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
Among the possibilities I've read mentioned are that it might have a much brighter surface than everyone has been thinking, and therefore it is smaller. Or it might be a binary object (or triple, or multiple). Maybe both. Being smaller and/or an orbiting pair would make it more likely to "slip through the cracks". That is, the shadow(s) could pass unseen through the spaces between the observing telescopes with higher probability. Were there any backup observations outside of the calculated 100 mile wide path? Now that I think about the 5 hour time delay for light from Pluto, and 7 hour time delay for MU69 it's rather amazing that the occultation "starts" and then it takes 7 hours for the shadow to reach us. |
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Jul 7 2017, 11:35 AM
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#399
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
the orbit of MU69 appears to be well established, with residuals of 0.02 arcseconds, according to the IAUC. I have no idea of how much that would mean for the occultation path width.
http://www.minorplanetcenter.net/db_search...ct_id=2014+MU69 also, I didn't know that all the observations of MU69 available have been made by the HST |
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Jul 7 2017, 12:22 PM
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#400
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
the orbit of MU69 appears to be well established, with residuals of 0.02 arcseconds, according to the IAUC. I have no idea of how much that would mean for the occultation path width. http://www.minorplanetcenter.net/db_search...ct_id=2014+MU69 also, I didn't know that all the observations of MU69 available have been made by the HST Um, apologies, (engineer brain and significant figures kicking in) but my quick trigonometry calculation
at 44 AU 1 arc second = 18k miles, and .02 arcsecond = 360 miles. shows that the location of MU69 is only accurate to within ~360 miles. Admittedly, that is amazing precision when you think about it. If the location of the object is accurate to .02 arcseconds then the location of the object's shadow cannot be known more accurately. The error bars are the same ~360 miles. -edit- Ok the prime eclipse path was not the only place where telescopes were deployed http://www.boulder.swri.edu/MU69_occ/june3.html -edit- Ah, found it. Yes, the eclipse path is calculated out to 3 sigma, so it's just under 900 miles wide. Ok, so it's really a picket fence problem, looking for a 30 mile wide shadow somewhere in a 900 mile wide swath. Estimates of Shadow Track- https://www.google.com/maps/d/viewer?mid=1z...0000046&z=2 |
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Jul 7 2017, 03:12 PM
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#401
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
Would a successful observation in the second or third occultation help ascertain where the first track actually was, and could they verify it was a 'picket fence' problem with the first one ?
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Jul 7 2017, 05:57 PM
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#402
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Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
Would a successful observation in the second or third occultation help ascertain where the first track actually was, and could they verify it was a 'picket fence' problem with the first one ? It should. If you can confirm seeing the 2 second occulation you'd nail down a location within the 100 mile occultation band; but if you only get 1 observation site, you still have 200 mile wide uncertainty, because you won't know whether you're in the top, center or bottom of that 100 mile band. Next comes a critical decision: A ) space the telescopes further apart because the shadow of MU69 might be north or south of what was calculated. B ) space the telescopes closer together because the shadow of MU69 might be narrower than projected. C ) keep things the same, because you're uncertain about your uncertainties. Tough call. |
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Jul 7 2017, 06:35 PM
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#403
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Member Group: Members Posts: 910 Joined: 4-September 06 From: Boston Member No.: 1102 |
D) enlist more telescopes and place them closer together in a much wider track
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Jul 10 2017, 03:58 PM
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#404
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Member Group: Members Posts: 204 Joined: 14-April 06 From: Seattle, WA Member No.: 745 |
All planetesimals born near the Kuiper Belt formed as binaries
https://arxiv.org/abs/1705.00683 Could it be that we are going visit a couple (or more) of primordial planetesimals? Go SOFIA! |
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Jul 10 2017, 07:29 PM
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#405
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Senior Member Group: Members Posts: 1582 Joined: 14-October 05 From: Vermont Member No.: 530 |
Go SOFIA! Already went https://twitter.com/SOFIAtelescope (I have to admit I was thinking "night" of July 10 was a few hours hence... but good to see it got its observations) |
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