The life of Carl Sagan now fills the tabletops of two vast rooms in the Madison Building of the Library of Congress. The life arrived in recent weeks at the building’s loading dock on 41 pallets containing 798 boxes.

Sagan famously talked about billions of stars and billions of galaxies, and it appears that he saved roughly that many pieces of paper.

The material documents Sagan’s energetic career as an astronomer, author, unrivaled popularizer of science and TV star, and it ranges from childhood report cards to college term papers to eloquent letters written just before his untimely death in 1996 at age 62. Also in the mix are files labeled F/C, for “fissured ceramics,” Sagan’s code name for letters from crackpots.

And there’s this, from Johnny Carson, after Sagan declared that he’d never actually used the much-satirized phrase “billions and billions” on “The Tonight Show”: “Even if you didn’t say ‘billions and billions’ you should have. — Johnny.”...