All of my speculative answers are 100 percent accurate! Every astronomer is entitled to their own professional opinion about things for which little or no data is available, such as Did physical laws exist before the Big Bang? or questions such as What exists beyond the current universe into which the universe is expanding?. I give questions such as this my best shot, based on the very speculative literature I have come into contact with throughout my career.
We are not, however, entitled to our professional opinion about observational facts. Questions requiring factual answers such as What is the distance to Mars? or others like How heavy can stars get? are answered to the best of my ability based on whatever tables and technical references I have at my fingertips. Usually these kind of questions are as accurate as astronomers can make them with our current understanding and technology. However, on a very concrete question Does Planet X exist? I started the essay with a bogus statement that Percival Lowell discovered Pluto, when I had meant Clyde Thombaugh, so I confess that even for pretty rock solid facts, I fully admit to being fallible. I have, fortunately, not received more than 10 notes from readers catching significant errors in my 1300+ answers. This doesn't mean that these errors do not exist, only that no one has come forward with discoveries of more factual errors in what I write.
I confess to being somewhat weak in the area of observational cosmology and in theoretical cosmology. These are not my areas of specialization, however, the feedback I have received from cosmologists and theoretical physicists who have read my various Sky and Telescope and Astronomy magazine articles, indicates that my paraphrasing of what theoreticians are saying about processes in the early evolution of the universe is in good shape. I shudder at questions about expanding space, because I simply have no idea how we humans can ever come to an understanding of such a process, and I feel I have been very repetitive in my answers about these matters. The mathematics are quite clear about interpretations, but I cannot marshal any of the mathematics in support of my answers because to do so would make this site far too technical for the average reader. Sorry.
As for everything else, all opinions and speculations should be taken with a grain of salt. I state the current situation in astronomy as accurately as I can, and use primary references whenever possible to get as close to the source as I can!