7planet x planet x, or planet 9, is briefly mentioned at the end of module 07. look up other information on your favorite web search engine, and discuss the following questions. 1. how probable is it that it really exists in your view? argue your reasoning. 2. what are its orbit characteristics? how do they compare to the orbit characteristics of uranus and neptune? 3. where in the sky should astronomers concentrate their efforts to find it? 4. if it does exist, what is the likely origin? is it part of the original solar system, or captured later from some other source?