The Coldest and Farthest Place in the Solar System

The farthest known object orbiting the sun is not Pluto. Comets are known to range out much further than Pluto, but here is also another object that is larger than Pluto that orbits at a distance three times greater than Pluto. It is a scattered disk object known as Eris, which is a dwarf planet, and its average orbit is 96.7 AU. For a short time, it was even designated as the tenth planet in our solar system until several other similar objects were found. Eris and its sister objects had a hand in the demise of Pluto's designation as the ninth planet. Eris even has its own moon that is called Dysnomia.

Eris has a highly elliptical orbit that is more elongated then Pluto's orbit. Like Pluto, Eris intersects the orbit of Neptune when it makes its closest pass to the the sun. Thus it is also designated as a Trans-Neptune Object (TNO). A single orbit of Eris takes a whopping 557 years.

Spectroscope observations of Eris have determined that the surface of Eris is quite similar to Pluto. It is made up of icy methane. When it makes closer passes to the sun, some of the methane may sublimate to form a shallow atmosphere, but that is a matter of conjecture.

Eris is a cold place. Temperatures are as cold as about -250 degrees Celsius. This is just a few tens of degrees warmer than absolute zero on the kelvin temperature scale, which is about as cold as it could get!