Reply To: What if?

You are quite correct. In fact, this is much more a “double planet” than the Earth-Moon system ever dreamed of being.

I could do the calculation, if I knew the distance and diameter of Charon.

(*checks Wikipedia, which must surely be getting edited hourly on this topic right now.)

1207 km wide at a distance of 19571 km (center to center). However, you have to subtract Pluto’s radius from that number, because that’s where you’re standing when Charon is directly overhead. That’s 1184 km. So the distance from our hypothetical observer to the center of Charon is 18,387 km

Simply divide, and you’ll get 1207/18,387 = 0.0656. That’s in radians, in degrees, it’s 3.76. That turns out to be 7.5 times as wide as the full moon (or the Sun) as seen by us here on Earth.

[Note: this is a back of the envelope calculation, and doesn’t account for the fact that Charon’s limb, as seen from Pluto, is going to be a bit closer than its center is. Plus there’s always the chance I made some silly error of fact or of computation that someone will come along and correct (and if so, thanks in advance).]

And yes, that’s a spectacular picture. It shows a sharpness of detail that will be great to see as the spacecraft gets closer over the next few days. I hope it survives long enough to return all of the data it is collecting, as mentioned before there is some non-zero but otherwise unquantifiable debris hazard when it goes through the system.