Item from Project Hail Mary by Andy Weir
A single-celled organism that eats stars — humanity's extinction event and its only ticket to the stars, wrapped in the same microscopic package.
The Astrophage is the most efficient energy storage system in the universe and it is eating the Sun. Each cell absorbs electromagnetic radiation and converts it directly into mass — E=mc² running in reverse, with no measurable energy loss. When releasing stored energy, it converts mass back to Petrova-frequency infrared light and uses the photonic force for self-propulsion. A single Astrophage cell contains more energy per gram than any fuel humanity has ever conceived. This dual nature — existential threat AND revolutionary fuel source — is the central irony of the story. The thing killing the Sun is also the only thing powerful enough to send a ship to another star to find the cure. Komorov realized this first: if you can control Astrophage, you can build a spin drive. If you can build a spin drive, you can reach Tau Ceti. If you can reach Tau Ceti, you might find out why it isn't dying. The lifecycle is elegant in its horror: feed near a star until saturated, follow magnetic field lines outward, breed on a CO2-rich planet, return to the star with offspring. Population growth is exponential. The Sun dims a fraction of a percent more each year. The math is simple and merciless.
A single-celled microorganism, visible under standard microscopy. Individually unremarkable — a tiny biological cell that stores energy as mass via neutrino pair production. En masse, they form the visible Petrova line: an infrared arc between a star and its breeding planet, glowing at the Petrova frequency. They are attracted to specific infrared wavelengths: 4.26 micrometers and 18.31 micrometers (carbon dioxide absorption lines).
Also known as: Astrophage, The Astrophage