This supernova's late brightness requires a spinning neutron star engine.

Astronomers detected a brief, energetic burst of X-rays from deep space called EP250304a. Soon after, they noticed it was linked to an exploding star, supernova SN 2025fhm. Supernovae usually shine because radioactive elements created in the blast slowly decay. But this explosion stayed far brighter at late stages than standard radioactive decay can explain. To solve this mystery, researchers tracked the event using X-ray, optical, and radio telescopes and ran computer simulations. They found that a shocked cocoonshocked cocoonA model where the supernova's jet plows through surrounding material, creating a hot bubble that glows. of gas explains the early cooling over the first 3 days. To explain the extra energy from 3 to 88 days, they discovered that a central engine must be pumping in power. The best fit is a magnetarmagnetarA neutron star with an extremely strong magnetic field, often thousands of times stronger than ordinary neutron stars., which is a rapidly spinning, highly magnetized neutron star. This spinning magnetar can account for both the late-time brightness and the unusual early pulses of X-rays.

Why it matters

When a star explodes, we usually understand its glow as leftover radioactive material cooling. But this supernova stays too bright too long. That means something else is pumping energy in — a rapidly spinning neutron star with an extreme magnetic field. It changes how we think fast X-ray flashes from space are connected to supernovae.

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