Varuna is a transneptunian object with a diameter of about 800km: it is much smaller than Pluto and it is much more far away.
The biggest known transneptunian objects (Wikipedia)
It has yet not been classified as a dwarf planet, but some reasearchers point out that it should be included into that category. To do so it is necessary to make telescopical observations of the TNO. The most important observations occur when the object crosses over a star reducing its brightness.
Some days ago we received a notification of Varuna would be eclipsing a magnitude 16 star near the Gemini constelation. The brightness of the star would be reduced more than 4 magnitudes and what it would be better, the occultation could have been visible from our latitude.