If another star crossed the asteroid belt, I think we would see it coming from a long distance away. I haven’t heard of a comet big enough to look like a star.
NEWLY DISCOVERED COMET ELENIN FITS THE DESCRIPTION OF PLANET NIBIRU AND HAS A TAIL...YOU CAN WATCH THE SIMULATION AT
http://secchi.nrl.navy.mil/STEREOorbit/C2010_X1.html