A kitchen timer ticks once a second. The neutron star SRGA J144459.2-604207 ticks 448 times a second: that's its own rotation, and it shows up in X-ray bursts. In 2024, the star woke up and started throwing thermonuclear explosions on its surface, like a bubbling pot of boiling water.
Three telescopes (NICER in orbit, XMM-Newton, and NuSTAR) kept an eye on the star. They caught 39 bursts during the observations. In two of them, from XMM-Newton and NuSTAR data, a brightness tremor appeared with a frequency of 447.7–448.0 Hz. This is the first detection of oscillations from this source. The strongest tremor in XMM-Newton data had a significance of 5.1σ (meaning the chance of it being random is less than one in a million), and in NuSTAR—5.2σ.
The signal shape is almost a perfect sine wave. In soft X-rays (0.5–10 keV), the tremor amplitude was 8.5% of the average brightness, and in hard X-rays (3–40 keV)—21%. That means a hot spot on the star's surface alternately shows itself to us and hides behind the edge, like a lantern on a spinning carousel. Interestingly, oscillations at 447.6 Hz were also noticed just before the start of one of the bursts: this has been seen only the second time in the history of observations.
A neutron star the size of a city spins faster than a blender—448 revolutions per second.
In Robert Forward's novel Dragon's Egg, creatures live on a neutron star for whom a second feels like an hour to us.