01 of 12Radio pulsar
PSR B1919+21
The first pulsar ever found
0.748turns
per second
One turn every 1.337302 s
You hear 45 beats a minute
Hear the real telescope recording
Since you tuned in: 0
Signal
01 of 12Radio pulsar
The first pulsar ever found
0.748turns
per second
One turn every 1.337302 s
You hear 45 beats a minute
Hear the real telescope recording
Since you tuned in: 0
Twelve pulsars · real spin rates · live sound
A pulsar is the collapsed core of an exploded star, spinning like a lighthouse and sweeping a radio beam past Earth once every turn. Each tick you hear here is played at the star’s true rate: from one that turns once every 76 seconds to PSR J1748−2446ad, which turns 716 times a second.
Or go straight to the fastest spin known or the first pulsar ever found.
Headphones help with the low ones. Light pulses are softened for fast spinners; you can calm the visuals further under How it works.
Each tick is one turn of the star. The rate is the pulsar’s measured spin; the shape of each pulse, the way single pulses vary from turn to turn and the receiver hiss are simulated live in your browser, in the style of radio-telescope recordings. Telescope plays each pulse as a burst of radio noise, the way a receiver hears it. Clean clicks turns each pulse into a crisp tick.
Below about ten ticks a second you hear separate beats. Between roughly ten and twenty they smear into a flutter. Above about twenty a second your ear fuses them into a musical note, which is why millisecond pulsars sing. The tuning dial marks these three zones. Use Time to slow a fast pulsar down until its note falls apart into ticks.
A neutron star packs about 1.4 times the Sun’s mass into a ball some 24 km across, so its spin is extremely hard to disturb. The steadiest millisecond pulsars keep time with a long-term stability that rivals atomic clocks. Timing dozens of them together turns the galaxy into a gravitational-wave detector: in 2023, pulsar timing arrays around the world reported evidence for a background of gravitational waves washing through the Milky Way.
The plaques on Pioneer 10 and 11 and the covers of the Voyager Golden Records carry a map that locates the Sun relative to 14 pulsars, each tagged with its period written in binary.
f = 1 / P spin rate from the measured periodRLC = c / 2πf light cylinder: where anything turning with the star would have to move at light speedv = 2πRf speed of the equator, taking R ≈ 12 kmτ = P / 2Ṗ characteristic age, from how fast the spin is slowingB ≈ 3.2×10¹⁹ √(PṖ) G surface magnetic fieldSpin periods, spin-down rates and distances come from the ATNF Pulsar Catalogue and the discovery papers: Hewish et al. 1968; Large, Vaughan & Mills 1968; Staelin & Reifenstein 1968; Hulse & Taylor 1975; Backer et al. 1982; Wolszczan & Frail 1992; Johnston et al. 1993; Burgay et al. 2003; Hessels et al. 2006; Caleb et al. 2022. Distances are parallax measurements where one exists. The sky from Earth uses the XHIP compilation of Hipparcos stars (Anderson & Francis 2012) and the IAU constellation figures, packaged in d3-celestial by Olaf Frohn (BSD licence). The real recordings linked on six of the pulsars are from Jodrell Bank Observatory. The scenes are illustrations: real pulsar beams are invisible radio waves, sizes and orbits are not to scale, and orbits are sped up so you can see them move. The supernova replay is artistic, and the glitch is exaggerated about ten thousand times so that you can hear it.