When astronomers found a large world farther out than Pluto, it became one of the final nails in the coffin of our ninth ...

The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

Two dwarf planets within our solar system, named Eris and Makemake, might exhibit enough geothermal activity to maintain oceans of liquid water within, according to modeling that describes new ...

Named Eris and Makemake, these celestial bodies ... the prospect of finding water in the icy outer reaches of our solar system. The findings are detailed in two papers published in Icarus.

is a disc-shaped region beyond the orbit of Neptune’s in the outer solar system—50 Earth-sun distances—that’s home to dwarf planets like Pluto, Makemake and Eris. It’s also thought to be ...