Because of its distance from the Sun, Persephone was not detected for many centuries. However, the effects of its gravity were detected in the orbits of several distant celestial bodies, called extreme Kuiper Belt objects. As a result, Persephone was inferred to exist - in some theories as Planet 9 - before being definitively discovered.
Perspehone orbits the Sun once every 20,000 years. It is about 480,000 light-seconds from the Sun, and its surface temperature is 20 K (-253°C, -423°F).