Jocelyn Bell Burnell Sticker

The sticker says She Found Pulsars. They Gave Her Silence. The first half is exactly right. The second is more complicated, as she has said herself.

In 1967 Jocelyn Bell, a Cambridge graduate student who had helped build a large radio telescope, was reading its chart-paper output for twinkling quasars when she noticed a signal that did not belong: pulses, extremely regular, a little more than a second apart. She took it to her supervisor, Antony Hewish. The team spent months ruling out interference, half-jokingly calling it LGM, for little green men. Then she found a second, elsewhere, at a different rate. The paper appeared in Nature in February 1968, her name second of five. It suggested the pulses might come from white dwarfs or neutron stars.

The first formula on this page is how that was settled. Anything that spins and holds together needs its own gravity to beat the spin, which puts a floor under its average density: about 3π divided by G times the period squared. A pulsar reported in 2006 spins 716 times a second, so its density must exceed about 7 × 10¹⁶ kilograms per cubic metre, far beyond any white dwarf. Only a neutron star, as dense as an atomic nucleus, survives. The second formula weighs the space between: lower radio frequencies arrive later, delayed by free electrons.

The 1974 Nobel Prize in Physics went to Hewish and Martin Ryle. Prominent scientists protested her omission; she has said leaving out a student was appropriate. Recognition followed: the 2018 Special Breakthrough Prize in Fundamental Physics, whose $3 million she gave away to help under-represented students become physics researchers, and in 2021 the Royal Society's Copley Medal.

Silence is the wrong word. The pulses were never silent, and neither was she.