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- 10 Hygiea on Wikipedia
10 Hygiea
Details
10 Hygiea is the fourth-largest object in the asteroid belt. In 2019 the VLT's SPHERE instrument revealed it to be very nearly spherical, which would make it the smallest known dwarf planet — a body massive enough for gravity to pull it into a round shape, yet only about 430 kilometers across.
10 Hygiea matters because it sits right at the boundary between asteroid and dwarf planet. It is the fourth-largest body in the main belt, a dark, carbon-rich object that for nearly two centuries was treated as just another large asteroid. Then high-resolution imaging changed how we see it.
In 2019, astronomers using the SPHERE instrument on ESO's Very Large Telescope resolved Hygiea's disk and found it surprisingly round — round enough that gravity, not chance, must have shaped it. That is one of the defining criteria for a dwarf planet. If confirmed, Hygiea would be the smallest known dwarf planet, smaller than Ceres yet still pulled into a sphere. Unusually, it shows no large impact crater, suggesting it reassembled from debris after a major collision long ago.
That is why Hygiea belongs on this scale. It blurs a category we often treat as clean, showing that 'asteroid' and 'dwarf planet' shade into each other. Hygiea is the reminder that roundness, and the gravity behind it, can appear in bodies much smaller than a planet.
190km
Visual creditESO / P. Vernazza et al. / MISTRAL algorithm (ONERA/CNRS) / CC BY 4.0Source: Wikimedia Commons
Key facts
- Category
- Asteroids
- Object class
- C-type asteroid / dwarf-planet candidate
- Mass
- ~0.000014 Earth masses
- Scale fact
- 434 kmmean diameter
- Estimated age
- ~4.5 billion years
- Composition
- Carbonaceous rock and ice
Scale context
Where 10 Hygiea sits on the full axis
Shared physical scale
438km
Together, these objects make the size change around 10 Hygiea easy to compare at a glance.
Sources
References for 10 Hygiea
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- 10 Hygiea — Wikipedia
- Visual reference: Wikimedia Commons (ESO / P. Vernazza et al. / MISTRAL algorithm (ONERA/CNRS), CC BY 4.0)
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.