Starship Asterisk*

Ultima Thule Rotation Gif

Explanation: Ultima Thule is the most distant world explored by a spacecraft from Earth. In the dim light 6.5 billion kilometers from the Sun, the New Horizons spacecraft captured these two frames 38 minutes apart as it sped toward the Kuiper belt world on January 1 at 51,000 kilometers per hour. A contact binary, the two lobes of Ultima Thule rotate together once every 15 hours or so. Shown as a blinking gif, the rotation between the frames produces a tantalizing 3D perspective of the most primitive world ever seen. Dubbed separately by the science team Ultima and Thule, the larger lobe Ultima, is about 19 kilometers in diameter. Smaller Thule is 14 kilometers across.

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Please note that, at present, the date at the top says "2019 January 3".

Also, the Discuss link on the APOD page currently points to yesterday’s forum thread.

Pretty good sized rock floating out there! I Hope it stays out there! Amazing what man can do these days.

orin stepanek wrote: ↑Fri Jan 04, 2019 3:45 pm Pretty good sized rock floating out there! I Hope it stays out there! :lol2: Amazing what man can do these days. 8-)

A good chance it's more ice than rock.

Case wrote: ↑Fri Jan 04, 2019 7:40 am Also, the Discuss link on the APOD page currently points to yesterday’s forum thread.

Thanks, missed that, as I used a bookmark instead of the link.

Chris Peterson wrote: ↑Fri Jan 04, 2019 11:53 pm

orin stepanek wrote: ↑Fri Jan 04, 2019 3:45 pm
Pretty good sized rock floating out there! I Hope it stays out there! Amazing what man can do these days.

A good chance it's more ice than rock.

Kuiper belt objects are pretty dense to be considered mostly ice:

Well nil rotation is out as an explanation of the flat light curve. It was a very long odds long shot, but worth mentioning just in case this unlikely possibility proved out to be the solution.

I note however that the axis of rotation does not appear to be aligned with the centers of mass of the two lobes, as would be expected if the two parts merely orbited together I would think. Therefore, I suggest that Ultima and Thule formed separately but orbited the sun on nearby orbits. Their very low gravitational attraction brings them together with an impact slow enough to prevent the disruption of either body. Then they essentially freeze together into one object.

Bruce