consider two parallel universes like membraines. if a blackhole exists on the first universe then it vil bend the space time graph to an infinite point as we know. but since there exists another universe v can say that the bented spacetime of the above vil converge vit the unbent spacetime of universe below. thus creating a wormhole.if v think logically then matter or energy absorbed should b emmited by the wormhole hence creating a gate from one world to another. so the wormhole can be called as an antiblackhole.if v think conversly then there also can exists an antiblackhole in our universe. this can be the high emitting light source. so if there is a shinning source about 500 light yrs away v might predict that it may be a supernova but to see the explosion v have to catch a guy who is 500yrs old !! i now this is theorotical but i got this idea from the thread posted by shaan argon. thanks to him who made me think !!!!!!