Preliminary Results Published From New Horizons Flyby of MU69 'Ultima Thule' (arxiv.org) 35
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.
Editing, anyone? (Score:2)
Today I learned that operators like =/- exist... in some minds at least.
And if the reason for a bright region to mark the junction between the two lobes is not known, then maybe there is no reason to have one, and we should look for the reason that there actually is one.
Re: (Score:2)
And your list of accepted submissions is how long?
Re:So why the lack of the light curve? (Score:4, Informative)
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.....
Re: (Score:3)
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.
Re: (Score:3)
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/1812.0 [arxiv.org]
Re: (Score:2)
I almost forgot why I normally exclude ACs from even being read.
Re: (Score:3)
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 brigh
Re: (Score:2)
"All planetesimals born near the Kuiper Belt formed as binaries"
https://arxiv.org/abs/1705.00683