It's around 43.4 AU from the sun, so sunlight at its surface would be close to 1/1900th as bright as at Earth. That corresponds to nearly 11 photographic stops fainter. So still quite a bit brighter than under a full moon at Earth, which would be around 18 or 19 stops fainter than full sunlight.

Latest image on NASA TV! Looks like a bowling pin.

Hal Weaver says the pole is facing us (explanation for the light curve mystery).

Failsafe 2.

We can see the rotation. Rotation period is either 15 hours or 30 hours.

More like somewhere between 15-ish and 30-ish hours - they didn't observe it at the higher resolution for long enough to pin the rate down well.

They said they're still not sure whether it's one or two bodies. Now that we have a (crude) rotation rate and a good size, it shouldn't be hard to estimate whether the periodicity is consistent with Kepler for two bodies, assuming something about density...

Though of course the uncertainties on linear size are still large, and the uncertainties on volume (and hence mass) will scale like the cube of the linear size (and depend on the full 3-D shape), so will be huge.

Another round of high-fives for Alan Stern and his team.

Looks to me that this might indeed be a binary.

When using this equation: P^2 = [ 24 pi R^3 ] / [ G rho (D1^3 + D2^3) ]
(with P = period -- 15 h or 30 h; R = range between component centers; G = 6.67e-11 m3/kgs2; rho = object density; D1 = diameter of larger, D2 = diameter of smaller component),

then, a P near 15 h can be achieved with the following values:
Assume rho = 0.6 g/cm3 => values for the range and sizes:
R ...12 -- 13 -- 14 -- 15 km
D1... 9 -- 10 -- 11 -- 12 km
D2... 7 -- 7 -- 8 -- 8 km

For P ~ 30 h and rho ~0.5, possible values are:
R ...16 -- 17 -- 18 -- 19 km
D1... 9 -- 9 -- 9 -- 10 km
D2... 5 -- 6 -- 7 -- 7 km

For a density similar to Phoebe's (1.6 g/cm3), the 15 h period might work like this:
R=18 km
D1=10 km
D2=7 km

The 30-h period at 1.6 g/cm3 does not appear to look compatible with the image to me:
R=18 km
D1=6.5 km
D2=4 km


Not surprising, it appears that we need the better images (plus the exact period) to get solid numbers. In the meantime, excitement remains that Ultima Thule might indeed be a double object.

~~ Tilmann

If it is a double object, they should dub the two parts "Ultima" and "Thule." (Like Buda and Pest.)

The ground illumination should look like about 10 minutes after sunset on Earth.

this is amazing... to the New Horizon Team! To the builders, the managers, the engineers, and to the thousands running the infrastructure that to talks to that little beauty! We need more of these machines... to bring our eyes out there! Well done!

https://planetary.s3.amazonaws.com/assets/i...tation_f233.gif

Here, it really looks like a contact binary. We will see...

Quick Crop:

Very interest the hypotetical luminosity over these astronomical distant corps.

I hope in a low distant binary, not in contact ��