Though Pluto has formally been considered a dwarf planet for almost two decades, it still has many lessons left for planetary scientists — including hints about how the solar system formed.

U.S. astronomers hunting for "Planet Nine" have instead stumbled on what appears to be a new dwarf planet in the solar system's outer reaches.

The dwarf planet Makemake, which chills out in the deep freeze of the outer Solar System, might be home to an ice volcano 1. Makemake is one of many icy worlds that orbit the Sun past Neptune.

In a distant region of space thought to be empty, a newly discovered dwarf planet inspires a debate about the existence of a giant planet hiding out there.

Pluto hasn't been a planet for almost 20 years. In the early 2000s, scientists discovered several objects of a similar size to Pluto. So, during the summer of 2006, members of the International ...

Dwarf planet Eris’ rotation is constrained by its large moon Dysnomia, named after the Greek goddess of lawlessness.

The small world was found during a search for the hypothetical Planet Nine, and astronomers say the next time it will reach its closest point to the sun is in the year 26186.

Astronomers think that a dwarf planet hiding in the middle of our solar system could be a source of frozen water. The dwarf planet Ceres is located in the asteroid belt between Mars and Jupiter. A ...

Astronomers have discovered a freezing-cold world orbiting within the so-called "forbidden zone" around a dying star in which planets are normally destroyed. The 5.8-billion-year-old white dwarf ...

Astronomers in Japan have published their theory of an "Earth-like planet," dubbed Planet Nine, that's hiding in plain sight just a few billion miles behind Neptune.

Astronomers have discovered an Earth-size planet orbiting a red dwarf star, making just the second planetary system seen around one of these tiny, cool, dim, but common, stars.

Arizona has declared Pluto as its “official state planet” — despite it being relegated to “dwarf planet” status nearly two decades ago.