Asteroid in front of galaxy

This looks like an asteroid passing in front of a galaxy, and to my eye it looks like the asteroid has a “tail”. After exploring it in the CAS viewer though, it looks like the “tail” is space between galactic arms.

Yep, looks to me like a pretty typical asteroid in front of a pretty typical spiral galaxy. If you flip over to the DECaLS DR3 images (yellow because we haven’t gotten the g-band imaging there yet), you can see that dark spot looks like a dust lane after the asteroid is gone.