01Size20 kmTemp600,000 K (≈ 599,700 °C)
Neutron Star
A city-sized star with the mass of a sun.
StarStellar remnantCosmos
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Whatever is pulling the universe apart, faster and faster.
NASA / ESA / S. Beckwith (STScI) — Hubble Ultra Deep Field
Picture this
Dark energy fills every cubic metre of empty space — including the metres around you right now. It has no size of its own, only a direction: outward.
The expansion of the universe isn't just continuing — it's accelerating. A mysterious form of energy, present in every cubic metre of empty space, seems to be pushing it outward. It accounts for roughly 68% of everything there is, and we have almost no idea what it is made of.
Did you know?
The term 'dark energy' was coined in 1998 by cosmologist Michael Turner — chosen specifically because nobody knew what it was. Almost 30 years later, the placeholder name has held up because we still don't.
Last updated 2026-05-17
A city-sized star with the mass of a sun.
Earth's only natural satellite — locked to us forever.
Our reference grain of sand.