Antique/vintage/ancient.
Another word for not old is young.
Relative vector of velocity. "Bearing" is another possibility.
Stationary.
"Ancient" is another word for very old.
imaginary, pretend
An unusual object that is often old could be a curio.
The root word of orbital is "orbit," which refers to the path an object takes around another object in space.
Another word for 40 year old is 4 decades. 8D
It is average density.
Another word for an old female cat is a grimalkin.
old
aged