10 Neutron Stars With Abilities That Shouldn't Be Possible

Added: 2026-05-30

[00:00:00]Fine, let's start. In December 2004, a star 50,000 lighty years away changed Earth's atmosphere. One star, one burst from the other side of the galaxy. And we had no idea it was coming. That's the thing about neutron stars. They operate at scales and speeds that feel almost deliberately hostile to human comprehension. They are city-sized objects with the mass of the sun spinning thousands of times per second wrapped in magnetic fields so intense that the space around them behaves differently than space anywhere else.

[00:00:39]And every few years, one of them does something that makes physicists stare at the data and quietly say that shouldn't be possible. 10 of them. 10 things that shouldn't be possible. Let's go.

[00:00:54]Number 10. In 2003, astronomers detected something extraordinary. A magnetar, which is an especially violent type of neutron star emitting radio waves. That was already unusual. Most magnetars don't do radio. This one did, and we gave it the name XTE J18 197. And we watched it carefully. Then in late 2008, it stopped, not slowed down, not faded. gradually stopped. One day it was broadcasting. Then it wasn't.

[00:01:29]For 10 years, nothing. No signal. No signal at all from an object that had been the first of its kind ever detected in radio. Now, a magnetar going quiet isn't completely unheard of. They're volatile. They flare. They settle. Fine.

[00:01:47]But 10 years is a long time to hold your breath. And by 2018, most astronomers had mentally filed this one under probably done. Then on the 8th of December 2018, the Levelvel telescope at Jodil Bank Observatory picked up a bright pulseed radio signal. XTE J18 197 was back. Here's the thing, though.

[00:02:12]When they looked closely at the signal, it wasn't quite the same signal as before. The pulse profile had changed.

[00:02:18]The geometry of the emitting region, the specific shape and timing of how radio energy was pouring out of the star had physically shifted during the silence.

[00:02:29]Something changed inside that star during the decade it spent being quiet.

[00:02:35]We can't tell you what because we don't know. We couldn't see inside it. We could only read the letter it sent after it decided to start writing again and noticed that the handwriting had changed. A star 50,000 lighty years from Earth, silent for a decade, then without warning, different number nine. There is a pulser in the globular cluster Tzan 5 about 28,000 lighty years away named PSR Junes 482446 AD. It holds a record. It spins 716 times per second. 716.

[00:03:17]A kitchen blender tops out at around 500 rotations per second. And we think of that as impressively fast. This neutron star is faster. And a kitchen blender isn't a star. The equatorial surface of PSR J17482446 AD. The material right along its widest point is moving at roughly 24% of the speed of light. One quarter of the speed of light just as a surface condition. as in that's just what it's doing all the time. Now, at that spin rate, the star has to be almost impossibly small to hold itself together. If it were any wider than about 16 km across, the centrifugal force at the equator would exceed the gravitational pull and material would simply leave, flung into orbit, just gone.

[00:04:11]The only thing keeping this star in one piece is the fact that gravity at its surface is roughly 200 billion times stronger than Earth's. Which raises the obvious question, how did it get this fast? The answer is that it has a companion star and over billions of years it stole mass from that companion.

[00:04:32]And each stolen parcel of mass carried angular momentum with it. And the pulser used all of that to spin up incrementally across geological time scales until it hit 716 rotations per second and apparently decided that was enough. The companion star for its trouble now orbits the pulser every 26 hours. It also eclipses it for about 40% of every orbit. Which means this record holding light speed adjacent gravity monster of a pulsar gets briefly blocked from our view every single day by the star it robbed. It seems a bit ungrateful. Number eight, the categories we use to sort neutron stars feel solid.

[00:05:16]There are pulsers, rotation powered, spinning fast, emitting radio beams as they go. And there are magnetars powered by the decay of enormous magnetic fields, occasionally violent, the source of some of the most energetic bursts in the known universe. Different objects, different physics, different boxes. PSR JWM19 61227 would like a word. In late July of 2016, a previously ordinary radio pulsar emitted two intense hard X-ray bursts. These weren't radio pulses. These were the kind of high energy eruptions that magnetars produce.

[00:05:56]Fermy detected them. Swift detected them. 12 bursts in total across the active period. The X-ray flux jumped by a factor of at least 160.

[00:06:08]And then the radio signal disappeared.

[00:06:11]The star, which had been quietly doing its pulsar thing, went X-ray active in a way indistinguishable from a magnetar outburst and simultaneously stopped broadcasting in radio for weeks. Then the radio came back. The X-ray settled down and PSR J11196127 went back to being a pulsar.

[00:06:34]The reason this matters is that the magnetic field of this star about 4 * 10^ the 13th Gaus sits right in the borderland between pulsar territory and magnetar territory. It apparently needed only a brief internal rearrangement to tip over the line to stop being one thing and start being another and then tip back. We tend to think of the categories we've invented for objects in the universe as reflecting real distinctions, and they often do. But every so often, the universe sends something across a boundary we thought was fixed just to remind us that the map is not the territory. The border between a pulsar and a magnetar. Turns out it's more of a suggestion.

[00:07:22]Number seven. In 2019, NASA's NICER telescope, which is mounted on the International Space Station and designed to observe X-rays from neutron stars, published results from a detailed mapping of Pulsar PSR J3 pulen zoro451.

[00:07:39]And what it found broke something that had seemed unbreakable for 50 years. The standard picture of a pulsar's magnetic geometry is a centered dipole. Two poles, north and south, on opposite sides of the star, like a bar magnet.

[00:07:55]Hot spots at each pole. Antipod doll, symmetrical. It's the picture in every textbook. It's the picture that's been there since pulsars were discovered in 1967.

[00:08:08]Both hotspots on PSR J30 plus0451 are in the same hemisphere. Not opposite sides, the same side. One of them is crescentshaped. Both are pointing away from us toward the hemisphere facing the other direction. No centered dipole magnetic field can produce this. To get this geometry, you need something more complex. Higher order magnetic field configurations offset from the center multipolar in structure. Here's what makes this unambiguous.

[00:08:41]Two completely separate teams analyzed the same nicer data independently using different statistical models, different analysis frameworks, different code, and they both got the same answer, the same impossible geometry. It wasn't a glitch in the analysis. It was the star. 50 years of pulser diagrams, the two beam lighthouse, the two antipital poles.

[00:09:08]That picture is not wrong exactly. It applies to many pulsers, maybe most of them, but for this one, the textbook was quietly, firmly incorrect, and Nicer found the edge of the map. There are probably others. We're just now getting the tools sensitive enough to find them.

[00:09:29]Number six, the term black widow pulsar is astronomers being unusually poetic and unusually accurate. A black widow pulsar is a neutron star in a binary system that is actively destroying its companion. Not passionately, not dramatically. Methodically, over billions of years, irradiating the companion star with intense radiation, boiling off its outer layers, reducing it progressively from a full star to a planetary remnant.

[00:10:01]PSR J0952 0607 is the most successful black widow we know of. When Roger Romani and his team at Stanford published their results in July of 2022 using the KEK telescope in Hawaii, they measured the pulsar's mass at 2.35 solar masses plus or minus 0.17.

[00:10:24]That is the highest well-measured mass for a neutron star ever recorded. And it got there by eating. The companion, once a full star, is now roughly 20 times the mass of Jupiter. A large gaseous planet essentially still being heated, still being evaporated. It orbits the pulser every 6.42 hours, close enough to be blasted by radiation from a star that spins 707 times per second. That spin rate matters. Neutron stars are born spinning fast, but they slow down over time. The only way to spin this fast at this age is mass transfer. Stolen angular momentum from a consumed companion. Every bit of mass it took, it also took speed. The more it ate, the faster it went.

[00:11:17]Here's the strange part. The accretion of that mass also buried the pulsar's magnetic field. The more it consumed, the magnetically quieter it became. Its current surface magnetic field is about 60 million G. For a neutron star, that is almost nothing. The most massive known neutron star is also among the most magnetically inert and it sits right at the edge above approximately 2 to 2.2 solar masses. Current models suggest a neutron star should collapse into a black hole. PSR J0952 0607 is at 2.35. It has been consuming mass for billions of years and is still just barely a neutron star. The companion has about a Jupiter's worth of mass left, give or take. At some point, one assumes the math catches up.

[00:12:12]Number five, there is a line in pulsar physics called the death line. It's not metaphorical.

[00:12:19]Well, it is, but it maps onto real physics. As a pulser ages and slows down, the processes that generate its radio emission become less and less efficient. Below a certain spin rate, above a certain age, the electromagnetic machinery simply stops working and the pulser goes quiet, dead, silent. PSR J91 4046 rotates once every 75.885 885 seconds and it is still broadcasting in radio. To put that in context, before this discovery in 2022, the slowest known radioemitting neutron star had a period of about 23 seconds. PSR J Ozor 9011 446 is more than three times slower than that. By every model we have, it should have crossed the death line millions of years ago. It should be invisible. It isn't. Dr. Manisha Caleb's team at the University of Sydney found it using the Mircat radio telescope in South Africa and initially they almost didn't notice it. The source was identified from a single pulse. One lone radio blip caught while the telescope was observing something else. One accidental signal from a star that shouldn't be talking. When they followed up, it got stranger. PSR J0901446 emits in at least seven distinct pulse types. Seven different modes of emission. Some look like pulsar pulses.

[00:13:54]Some look like magnetar bursts. Some resemble fast radio bursts. Those bright millisecond duration flashes usually seen in distant galaxies. It has the highest magnetic field strength ever measured in a radio pulsar. A later study classified it as the most magnetized radio pulsar known. It does not fit in any box we currently have. A follow-up study pointed out that detecting sources like this is observationally very difficult because radio telescopes typically don't search for pulses this slow or pulses that last more than a few tens of milliseconds.

[00:14:34]Which raises the obvious question, how many others are out there? broadcasting from beyond the death line into a sky nobody is looking at. Number four, since the first pulsar glitch was recorded in 1969, astronomers have cataloged hundreds of them. A glitch is when a neutron star suddenly spins up, just slightly, just briefly. Typically attributed to angular momentum transfer between the stars superfluid interior and its solid crust.

[00:15:07]They're not fully understood, but they follow a clear rule. They are always spin-ups. Every glitch ever recorded had involved a neutron star rotating faster than it had a moment before until April of 2012. The Magnetar 1E 2259 Ply 586 was being monitored by the Swift X-ray telescope as part of a regular timing campaign. And on approximately the 18th of April, something happened. The pulsar's rotation frequency dropped abruptly. A sudden, clear, unambiguous spinown, an anti-glitch.

[00:15:45]The lead author, Robert Archabald at McGill University, described it precisely. What is really remarkable about this event is the combination of the magnetar's abrupt slowdown, the X-ray outburst, and the fact we now observe the star spinning down at a faster rate than before. A week before the timing anomaly on April 21st, a 36 millisecond X-ray burst had been detected from the magnetar's direction by Fairmy. The burst may have been a signal of whatever internal rearrangement caused the spinown.

[00:16:18]Or maybe the burst caused it. The causal chain isn't settled. One published explanation which reached peer review and was taken seriously is that a solid body, an asteroid like object struck the magnetar carrying retrograde angular momentum. Angular momentum pointing the wrong way and the star recoiled. A neutron star hit by a rock visibly flinching in the timing data. That might not be the right answer. Magnetospheric torqus and internal superfluid dynamics are the more mainstream candidates. But here's the thing, nobody has proven the anti-glitch mechanism definitively. And then in April of 2019, it happened again. A second anti-glitch, this time with no X-ray burst. No external signal at all. It just quietly spun down in isolation without announcing itself. The same star, the same impossible behavior, silent this time, internal, invisible except in the timing. The rule held for five decades and hundreds of observations. Then it broke twice.

[00:17:35]Number three. In 1974, a 24-year-old graduate student at the University of Massachusetts named Russell Hulse was conducting a systematic pulsar survey using the Araibo Observatory in Puerto Rico. He'd been finding new pulsars, cataloging them, moving on, routine work mostly. Then he found one where the period varied. A pulsar's period isn't supposed to vary. That's rather the point of a pulsar. They are famously some of the most precise natural clocks in the universe. A varying period suggested noise equipment artifact.

[00:18:14]Something wrong with the data. Hulse nearly discarded it. His supervisor, Joseph Taylor, talked him out of discarding it. What they had found was the first binary pulser, a neutron star in orbit with another neutron star. The period wasn't varying randomly. It was varying in a regular predictable pattern because the pulsar was Doppler shifting its own pulses as it moved toward and then away from Earth in its orbit. The variation was the orbit. They named it PSRB1913 pulsistine and started timing it carefully, very carefully. Here's what general relativity predicts. Two massive objects orbiting each other should lose energy by radiating gravitational waves.

[00:19:02]As they lose energy, the orbit should shrink. The orbital period should decrease slowly but measurably.

[00:19:10]Einstein's equations give you a very specific number for how fast. After eight years of observation, Taylor and his team reported the orbit was decaying at exactly the rate Einstein predicted to within a fraction of a percent. They had just proven that gravitational waves exist. Not directly. They hadn't detected the waves themselves, but they had detected the energy loss. And there was only one thing in physics that could carry energy away from that system.

[00:19:40]The Nobel Prize in physics for 1993 was awarded to Hulse and Taylor for the discovery. The direct detection of gravitational waves by LEGO happened in 2015, 41 years later. 41 years between indirect proof and the ability to actually hear them. Hulse almost didn't keep the data. The data almost became noise on the floor of an observatory in Puerto Rico. Instead, it became the first handshake between neutron star physics and gravitational wave astronomy because a graduate student found an anomaly in his timing measurements. And for once, someone said, "Wait, the universe had been broadcasting that answer for decades before we had the instrument to hear it clearly."

[00:20:29]Hul's pulser found the signal first.

[00:20:32]Number two, December 27th, 2004, 2130 UTC.

[00:20:40]A burst of gamma radiation struck Earth's upper atmosphere. Multiple spacecraft were hit simultaneously. Some had their detectors completely saturated, meaning the instruments simply couldn't measure how bright it was. They'd gone off the scale. Some automatically switched into protective modes. There were instruments aboard satellites that were not pointed anywhere near the source and still recorded the event because the signal was powerful enough to reflect off the moon and hit them from the other direction. The source was the magnetar SG180620 located approximately 50,000 lighty years away in the constellation Sagittarius. In 1/5 of a second, it released roughly 2 * 10 to the 46th urg of energy. to make that feel real. That is more energy than the sun will emit across the next 250,000 years. Released in a fifth of a second by one star that we didn't know was about to do this. The burst was so energetic that it ionized Earth's upper atmosphere, the ionosphere. It measurably changed the electromagnetic properties of our planet from 50,000 lightyear.

[00:21:57]After the initial burst, a radio afterglow was detected expanding outward from the magnetar at roughly 25% of the speed of light. The outflow contained at least four times 10^ the 43rd urgs in the form of magnetic fields and relativistic particles, creating a briefly resolved radio nebula that astronomers tracked over the following weeks. Now, here's the part where the scale stops being impressive and starts being something else. If SG180620 had been within about 10 lighty years of Earth, roughly the distance to our nearest stellar neighbor, the gamma radiation from that burst would have significantly depleted Earth's ozone layer. Depending on geometry and intensity modeling, some calculations suggest effects comparable to a mass extinction event. It was 50,000 lighty years away and it changed our atmosphere. There was no warning. SG1806 to 20 had been cataloged and monitored.

[00:22:59]Astronomers knew it was a magnetar. They knew magnetars occasionally flare.

[00:23:05]Nobody predicted this event. Nobody could have. We found out when the instruments registered it. when the sky on an otherwise unremarkable December evening briefly said something. Number one, this one is quieter than the rest.

[00:23:21]No flare, no blast, no asteroid strike, no alarm on a spacecraft, just a cooling curve, a small consistent drop in surface temperature recorded across a decade of observations. 2% per decade, a number that would mean nothing by itself except that it was too fast. The star was cooling faster than it should have been. And two separate groups of physicists on different continents, independently looking at the same Chandra X-ray data, arrived at the same explanation within weeks of each other without knowing the other was working on it. The neutron star in the Cassiopia, a supernova remnant sitting about 11,000 lighty years away, is approximately 330 years old. Young for a neutron star. It was first discovered in 1999 as part of Chandra's very first observations. Its surface temperature sits around 2 million Kelvin. And between 2000 and 2010, it cooled by roughly 2%.

[00:24:25]2% doesn't sound like much. 2% of 2 million degrees is 40,000° of temperature loss in a decade. And the reason matters more than the number.

[00:24:36]what Danny Page, Madapa Pash, James Latimer, and Andrew Steiner proposed in their February 2011 physical review letters paper. And what Peter Sternan and colleagues in St. Petersburg proposed independently at almost the same moment is that the cooling is caused by nutrinos, specifically by the onset of neutron superfluidity in the stars core. Superfluidity inside a star. You've probably heard of super fluids. Liquid helium cooled below about two Kelvin becomes one flowing without friction climbing walls defying intuitive behavior. The super fluidity in this neutron stars core involves neutrons.

[00:25:23]actual neutrons, the particles that make up the interior of every atom, pairing up into what physicists call Cooper pairs, like electron pairs in a superconductor. And when that pairing happens, when the neutrons undergo that phase transition, they emit a burst of nutrinos.

[00:25:43]Energy is radiated away. The star cools faster. The core of Cassiopia A's neutron star is sitting at roughly 5 * 10 8 Kelvin, which sounds enormous until you realize that this is cold enough for neutron superfluidity to occur. The protons in the core had already gone superconducting at higher temperatures years earlier before we were watching closely enough to see it. The neutrons are only now crossing their threshold.

[00:26:13]We watched it happen. Not a simulation, not a prediction, an observation. A quantum phase transition. Matter changing state at the subatomic level occurring inside an object 11,000 lighty years away. Detectable only as a tiny drop in surface temperature, measured across a span of years by a telescope in space. Two groups working in parallel, neither aware of the other. both arriving at the same answer. The physicists at Chandra headquarters when both papers landed close together later described it as a genuine race with a simultaneous finish. And here is the thing that is worth sitting with. We didn't watch this star explode. We didn't catch it in a burst or a flare or a collision. There was no event. There was just a measurement repeated consistently over a decade that came back slightly colder than the last time.

[00:27:13]And in that cooling curve in that patient, unremarkable line of data points trending downward was a record of something happening deep inside a collapsed stellar core that no instrument can directly observe. the most exotic form of matter in the known universe changing its fundamental state.

[00:27:33]And the only evidence was a 2% temperature drop on a surface 2 million degrees hot. The universe doesn't always make noise when it does something extraordinary. Sometimes it just gets a little colder. And if you're paying attention, you can find out what it's doing in the dark.

[00:27:51]Thank you for watching and sticking till the end. We've got plenty more videos coming in the future. Hit that subscribe button so you don't miss them.