Thanks to advancements in telescoptics (I made that word up just now) we are picking up new celestial bodies, likely having been there before, but only being seen for the first time.
In this case, a small orbiting moon, known as 2016 HO3, was witnessed with the Pan-STARRS 1 asteroid survey telescope in Haleakala, Hawaii on April 27, 2016.
The moon is tiny, registering larger than 120 feet (36.5 metres) across, but no more than 300 feet (91 metres) in width. Never getting closer than about 14 million kilometers from Earth or farther than about 40 million kilometers.
Though it is small, it’s been orbiting with us for a century and astronomers believe it will remain with us for another couple centuries, at least.
Source : minds