So why does this "planet" appear fully illuminated (rather than like a crescent or half moon)?
Because you are not seeing it by reflected light. You are seeing it by emitted light in the "short infrared" wavelengths. It's hot: 1000 C, which puts its peak radiance at around 2250nm. It's glowing.
15 posted on 07/02/2018 12:56:47 PM PDT by NorthMountain
(... the right of the people to keep and bear arms shall not be infringed)