http://legacysurvey.org/viewer?ra=177.5840&dec=-2.8067&zoom=15&layer=sdssco
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.
cheers,
–dustin