From the Washington Post:
Many astronomers remain convinced a once-in-a-generation discovery is in the offing — one that would rewrite textbooks down to the elementary school level. “Every time we take a picture,” said Surhud More, an astronomer at the University of Tokyo, “there is this possibility that Planet Nine exists in the shot.”
Circumstantial evidence continues to accumulate for the existence of Planet Nine, the hypothetical body thought to be lurking in our solar system far beyond Neptune. But no telescope has been able to spot it. Michael Brown, an astronomer at the California Institute of Technology, says he feels “eternally optimistic” that someone will soon find it, but there’s reason to believe that Planet Nine, if it exists, might be essentially invisible to existing observatories.