Somewhere in the constellation Draco, a dead star the size of a city is spinning so fast that it completes nearly 600 full turns in the time it takes you to blink. Astronomers have just found it, and it is one of the most extreme objects ever measured. The neutron star, named PSR J2053+6905, rotates about 597 times every second, with each turn lasting just 1.675 milliseconds. That makes it one of the ten fastest-spinning pulsars ever discovered, and the third-fastest of its particular kind. It also appears to be unusually heavy, packing more than twice the mass of the Sun into a ball only a few tens of kilometres across, while it slowly strips material from a smaller companion star in orbit around it.
The discovery was made with the Green Bank Telescope in West Virginia. An international team led by Anna Karpova combined four observing sessions between October 2025 and January 2026, seven and a half hours in total, with optical observations from telescopes in Mexico, Uzbekistan and the Canary Islands. Their findings were published on 5 November 2026 in a paper accepted by the Monthly Notices of the Royal Astronomical Society. This star sits near the physical limits of what matter can do, and measuring it may help physicists answer a question no laboratory on Earth can settle: how does matter behave when squeezed harder than anywhere else in the universe?
What exactly is a pulsar?
A pulsar is a neutron star, the collapsed core left behind when a massive star runs out of fuel and explodes as a supernova. The outer layers are blown into space, but the core collapses under its own gravity until it is unimaginably dense. A typical neutron star holds more mass than the Sun inside a sphere roughly the size of a city, about 20 kilometres across. A single teaspoon of its material would weigh roughly a billion tonnes.
Many neutron stars beam radio waves out from their magnetic poles. Because the magnetic poles are usually tilted away from the spin axis, those beams sweep around the sky like the light from a lighthouse. When one of those beams happens to cross Earth, radio telescopes catch a brief pulse of radiation once per rotation. That is why astronomers call them pulsars: from our point of view, they appear to pulse with clock-like regularity. The fastest ordinary pulsars spin a few times per second. PSR J2053+6905 spins 597 times per second, which is why it belongs to a special class called millisecond pulsars. Radio telescopes keep revealing new kinds of cosmic signals too, as shown by the Webb telescope finding the most distant fast radio burst, from deep space.
How a dead star learns to spin so fast
No neutron star is born spinning this quickly. When a massive star collapses, its core does spin up dramatically, in the same way that an ice skater spins faster when she pulls her arms in. But that alone gets a neutron star to perhaps a few dozen rotations per second, not hundreds. To reach millisecond speeds, a neutron star needs a companion.
Astronomers call the process recycling. In a close binary system, the neutron star's gravity pulls gas away from its companion star. That gas spirals inwards, forming a hot disc, and as it falls onto the neutron star it carries angular momentum with it. Over millions of years, this steady rain of matter gradually winds the neutron star up to hundreds of rotations per second. Eventually the flow stops and what remains is a millisecond pulsar, spinning furiously, with a companion that has been partly consumed. PSR J2053+6905 is a textbook example of what that long process leaves behind.
The redback: a star slowly eating its companion
PSR J2053+6905 belongs to a family of binary systems nicknamed spider pulsars, and more specifically to the subgroup called redbacks. The name comes from the redback spider, whose females sometimes eat their mates. In space the process is less gruesome but just as destructive: the pulsar's powerful wind of energetic particles and radiation slams into its low-mass companion star, heating it and gradually stripping its outer layers away into space.
In this system, the two stars circle each other every 7.47 hours, and the neutron star is about seven times heavier than its companion. The best estimates put the pulsar at roughly 2.1 times the mass of the Sun and its companion at about 0.3 solar masses, although those numbers are still model-dependent and carry real uncertainty. Optical measurements show the companion racing towards and away from us at up to 337 kilometres per second, and the pulsar's radiation heats the side facing it to about 5,550 Kelvin, while the far side stays cooler at around 4,960 Kelvin.
The companion is also changing in ways the researchers did not fully expect. Its brightness varies during each orbit, and the pattern of that variation has shifted between observations taken in 2023, 2024 and 2025. Heating alone cannot explain the changes, so the team suggests a large, relatively cool starspot may be drifting across the companion's surface or slowly fading away. That matters, because the mass estimates depend on how astronomers model the companion's glowing surface, so the pulsar's exact mass remains an estimate for now.
The system also has a habit of hiding. During one Green Bank observing session, the pulsar's radio signal vanished about 2,000 seconds into the observation, in what looks like a prolonged eclipse caused by gas streaming off the companion. That gas can absorb or scatter radio waves, briefly cutting off an otherwise clockwork signal.
How fast is 597 times a second, really?
Numbers like 597 rotations per second are hard to picture, so it helps to translate them. If this neutron star is about 20 kilometres across, a point on its equator would be travelling at roughly 37,500 kilometres per second, around 12.5 per cent of the speed of light. That is an illustrative calculation rather than a direct measurement of this star's size, but it captures the scale of the forces involved.
There is a reason no pulsar has ever been found spinning much faster than this. The fastest known pulsar, PSR J1748-2446ad in the star cluster Terzan 5, spins 716 times per second, a record that has stood since 2006. Physicists expect there is a hard limit somewhere not far above that. Spin a neutron star too fast and centrifugal force begins to rival gravity, threatening to tear the star apart. Some theories suggest gravitational waves generated inside the spinning star may act as a brake, carrying away energy and capping the spin rate. Two decades of searching have found nothing faster, which hints that such a limit is real, although its exact value depends on unknown physics. Every new fast pulsar near the top of the list sharpens that test.
Why astronomers care: weighing the densest matter in the universe
The real prize in this discovery is the mass. Neutron stars are the only places in the universe where matter is squeezed to such extremes, beyond anything a laboratory can reproduce. Physicists describe the behaviour of that matter with what they call an equation of state, essentially a rulebook for how dense nuclear matter responds to pressure. Many different rulebooks are on the table, and they make different predictions about the heaviest neutron star that can exist before gravity wins and the star collapses into a black hole.
That is why every heavyweight neutron star matters. If PSR J2053+6905 really does weigh about 2.1 times the Sun, it would rule out the softer rulebooks, the ones that predict neutron stars cannot get that heavy. Physics keeps producing surprises at the smallest scales too, as in the Bethe strings quantum prediction finally seen after 95 years. It would also tell physicists that the matter inside neutron stars is stiff enough to support such a mass while spinning at nearly 600 turns a second, since rapid rotation itself helps hold the star up against gravity. The measurement is not yet precise enough to settle the question alone, but it adds a valuable data point at the extreme end of the scale.
There is a wider point too. Millisecond pulsars are the clocks astronomers use to hunt for gravitational waves from merging supermassive black holes, by watching for tiny delays in their pulses. The more of these clocks we find, and the better we understand them, the sharper that cosmic detector becomes.
What is still uncertain
Honest science includes the gaps, and this discovery has several. The pulsar's exact mass is the biggest one: it rests on modelling the companion's light, and the companion's unexplained changing brightness means the number could shift as better models arrive. The team's observations were also spread across months, and they have not yet stitched together a continuous record of every single rotation between their separate observing sessions. Without that, the timing model that describes the pulsar's spin and orbit is still a first draft.
The long radio eclipse is another open question. Gas from the companion is the likely culprit, but how much gas there is, where it sits, and whether it changes over time are all unknown. And the starspot idea, while plausible, is an interpretation of shifting light patterns rather than a direct image of the companion's surface. None of this weakens the discovery.
What happens next
The research team plans further radio observations with the Green Bank Telescope and with CHIME, the Canadian Hydrogen Intensity Mapping Experiment. Those measurements should produce a continuous timing record and pin down the pulsar's spin and orbit far more precisely. Continued optical monitoring of the companion should also settle whether the changing brightness comes from starspots, variable heating, or a more complicated interaction between the two stars.
There may also be more objects like this one waiting nearby. PSR J2053+6905 was found by aiming at a gamma-ray source, 4FGL J2054.2+6904, that had already been flagged as a promising candidate from earlier X-ray and optical observations. The Fermi catalogue still holds many unidentified sources, and each one could be another extreme star or another test of matter at its limit.
For now, PSR J2053+6905 stands as a reminder of how strange the universe can be. A star died, collapsed into something the size of a city, was spun back up by stealing gas from its companion, and now turns nearly 600 times a second while it slowly devours the star that made it fast. It is a lighthouse and a laboratory all at once, and it is still spinning, somewhere in Draco, whether or not anyone is watching.
Sources: Karpova, A. V., Taylor, J. D., Bobakov, A. V., et al. (2026). "Discovery of the redback pulsar PSR J2053+6905 and multi-epoch optical observations of the system." Monthly Notices of the Royal Astronomical Society (paper accepted; published 5 November 2026). Above the Norm News, "Astronomers Discover Extreme Neutron Star Spinning Nearly 600 Times Every Second" (6 November 2026). Green Bank Observatory / National Radio Astronomy Observatory. arXiv:2306.17593 (Karpova et al., 2023, the earlier redback candidate study of 4FGL J2054.2+6904). Hessels et al. (2006), "A radio pulsar spinning at 716 Hz," Science (fastest known pulsar PSR J1748-2446ad).