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

The studies - both published in Icarus - look at something astronomers already knew: that Eris and Makemake, the second and fourth largest dwarf planets ... power to draw out more details from ...

Eight billion miles (14 billion kilometers) from Earth, at the solar system’s ragged edge, lies Eris — a planet-sized oddball of a world that emerged unexpectedly from the darkness 20 years ago.