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Preliminary Results Published From New Horizons Flyby of MU69 'Ultima Thule' (arxiv.org)
RockDoctor writes: The NASA/SWRI/Lowell Observatory (and at least 3 universities) team managing the download of data from New Horizons has released a first look at the results downloaded so far. At the time of writing, about 4 days of about 600 days of downloading had been completed. The next milestone hinted at is for March 2019 when the LPSC (Lunar & Planetary Science Conference) will get another batch of data as the various science teams get more data out of the pipeline.
Results: Firstly the overall shape -- as hinted by the occultation results from nearly a year ago -- is a contact binary. There is a lot of work going on from that, about how it could have formed, its accretion history and thermal history. The rotation period is better known (and this will improve as more data is downloaded) at 15=/-1 hours. The mass remains unknown. The mass ratio of the two components (nicknamed "Ultima" and "Thule") is suspected to be the same as their volume ratio -- 2.6:1; to get an accurate mass, observation of a satellite is needed, but the trajectory change for the spacecraft is unlikely to be large enough to estimate the mass well. Very little data has come down yet about the mineralogy, but the color suggests there is less water ice on MU69 than on Nix, the satellite of Pluto similar in size to MU69. The reason for a bright region to mark the junction between the two lobes is not known.
That'll be the sum of the data for the next 10 weeks until the 50th LPSC on March 18th.
Results: Firstly the overall shape -- as hinted by the occultation results from nearly a year ago -- is a contact binary. There is a lot of work going on from that, about how it could have formed, its accretion history and thermal history. The rotation period is better known (and this will improve as more data is downloaded) at 15=/-1 hours. The mass remains unknown. The mass ratio of the two components (nicknamed "Ultima" and "Thule") is suspected to be the same as their volume ratio -- 2.6:1; to get an accurate mass, observation of a satellite is needed, but the trajectory change for the spacecraft is unlikely to be large enough to estimate the mass well. Very little data has come down yet about the mineralogy, but the color suggests there is less water ice on MU69 than on Nix, the satellite of Pluto similar in size to MU69. The reason for a bright region to mark the junction between the two lobes is not known.
That'll be the sum of the data for the next 10 weeks until the 50th LPSC on March 18th.
Per the Wiki:
https://en.wikipedia.org/wiki/(486958)_2014_MU69
"Despite 2014 MU69's irregular shape, there is no detectable light curve amplitude, as its axis is oriented on its side, pointing towards the Sun."
They came on it from it's pole. Unfortunately, it didn't turn out to be Rama.....
Donald Trump, on a crusade to make Nixon look respectable
With the data that has downloaded so far (which is not a lot more than when I wrote the submission, because MU69 is close to the sun in the sky which interferes with the about 10^-20 W of signal from the spacecraft), they don't know the rotation rate well (15+/-1 hours) nor the orientation of the rotation axis. It is also possible that it is tumbling and has no rotation axis.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
That would imply that it's rotation axis is not far from laying in the fundamental plane of the solar system, similar to the Pluto/Charon system and Uranus. Which makes me go "Hmmm, interesting."
While no coherent light curve for MU69 has been modelled, there is variation in the brightness. See, for example, fig 5 of https://arxiv.org/pdf/1812.047... (caption includes "Although there is quite a bit of scatter in the data and we cannot determine the period, it is possible to hide a lightcurve amplitude of up to 0.6 magnitudes within this dataset.") "No rotation" is possible (but unlikely) ; slow rotation (much less than the 9 day intense observation campaign, for example) is also possible ; irregular rotation ("tumbling") is possible.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
Do you know any forces that reverse like that? I can only think of one that would work in space - if there were another body in orbit with the main body. Pushing, then pulling.
But - that is precisely why both Hubble and the cameras on NH have performed long exposure ("deep", to low brightness) searches of the vicinity of MU69 over the last couple of years. IF there is such a satellite, then it is either very small (I think the limit of 1.5km diameter has been mentioned) and so only capable of producing small forces, OR it is extremely dark (but can be larger, producing greater forces).
Data is coming. I fucking love science.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"