A thread topic doesn't preclude you from reading the articles that make it obvious that no one is claiming to KNOW anything. And perhaps you should read the whole article so you can be aware of the context.
"Although we were initially quite skeptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we become increasingly convinced that it is out there," says Batygin, an assistant professor of planetary science. "For the first time in over 150 years, there is solid evidence that the solar system's planetary census is incomplete."
There is enough statements in the article that make it clear this is an educated conclusion based on the available data. The fact that each and every time they talk about the planet, they don't say, "This is just evidence or we may be proven incorrect," doesn't change the fact that as scientists they are fully aware that this is simply an educated conclusion based on the data. If new data comes in that disputes their findings then they will revise their conclusions. That's the difference between faith and science.
And I will defend yours. That doesn't preclude me from pointing out the irony in people of faith commenting on something that may or may not exist in light of their beliefs.