Space

The sky is full of clocks

Pulsars are the most precise natural clocks in the universe — dead neutron stars sweeping a beam past Earth on a fixed period. Here is every one we've measured, placed on the galactic sky and blinking at its real spin period: millisecond pulsars flicker almost too fast to follow, second-long ones pulse slow and heavy. The bright band is the plane of the Milky Way. Tap or hover any clock; drag the slider to keep only the fastest and watch the sky thin to the millisecond swarms.

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clocks ticking

Showing all periods

Data & source

Source: ATNF Pulsar Catalogue (Manchester, Hobbs, Teoh & Hobbs 2005), via VizieR B/psr, fetched —. This is the compiled catalogue of — known radio pulsars with a measured spin period — the ones we've found and timed, not every pulsar that exists. Position is the pulsar's real place on the galactic sky (Hammer projection). Blink cadence follows each pulsar's true period, but compressed logarithmically so milliseconds and seconds can share one clock — a real millisecond pulsar spins hundreds of times a second, far too fast to see. Colour marks the population; the millisecond cut is the conventional 30 ms. Distances are model estimates and some are unknown.