as if black holes and neutron stars aren't weird enough physicists have very good reason to believe that there are even stranger stellar remnants out there stars made entirely of quarks the mathematics of modern physics that emerged through the 20th century explained so much about our universe but the same mathematics also hid some surprises there are monsters lurking in that math predictions of phenomena so extreme and bizarre that as with any monster it was hard to know whether to credit them with reality the most wonderfully monstrous of these are the remnant corpses of the most massive stars still as zombies like neutron stars and black holes Einstein's general theory of relativity tells us that the core of a dead star must collapse under its own incredible weight what happens to the resulting ultra dense material depends on quantum theory we've already talked about how quantum processes save a neutron star from collapse but ultimately also doomed the most massive to collapse into a black hole but just shy of that final transition and on the fringe of our understanding of the quantum universe a star may become very strange indeed literally I'm talking about strange stars before we can understand strange stars we need to start with the stellar remnants that we know for sure exists the neutron star these are weird enough all on their own they are created in the final collapse of a very massive stellar core after it has exhausted all possible fusion fuel suppliers in that collapse most of the electrons and protons are crunched together to form neutrons at a radius of around 10 kilometers the collapsing core is suddenly halted when those neutrons hit an absolute limit of density which I'll come back to the rest of the in falling star collides with the new neutral star and ricochets outwards in the most powerful explosion in the universe a supernova the remaining neutron star is millions of Kelvin in temperature and may be spinning thousands of times per second its immense magnetic field drives Jets of material at extreme speeds these Jets may sweep across the earth due to the spinning top like procession of the neutron star we see these as pulsars our understanding of neutron star seems to fit the behavior of pulsars very well at least for most of them but for some we see hints of weird things happening deep beneath the star surface which we'll get to for ordinary neutron stars that surface is a thin crust of iron which quickly gives way to a fluid of almost pure neutrons neutronium the dentist's known substance in the universe a cubic centimetre weighs a billion tons like I said this is the absolute limit of density well nearly as we'll see soon neutronium is degenerate matter and I don't mean that in the same way that your parents probably use the word the dinner at matter is so compressed that particles can't get any closer together without occupying the same quantum states the power Li exclusion principle states that this is forbidden for fermions the family of particles that neutrons belong to we don't know nearly as much as we'd like about the nature of neutronium we can't make this stuff in labs and we certainly can't test what happens to it when subjected to the insane pressures at a neutron stars core in those conditions individual neutrons are packed so tight that they begin to overlap this may cause neutrons to dissolve into their component quarks this so-called quark matter is it's very own type of bizarre we think that a type of gas like quark matter a so-called quark-gluon plasma filled the entire universe until around a millionth of a second after the bang the choir epoch and we have good reason to think that because we can actually make this stuff in our largest particle accelerators miniscule flecks of quark-gluon plasma exist for tiny fractions of a second after very high speed particle collisions we can study its nature based on the particles that decay from it however the quark matter in a neutron star is forged by insane pressures not by the greater than a trillion Kelvin temperatures of the quark epoch or the Large Hadron Collider in that state it forms a superfluid rather than a plasma a superfluid even denser than neutronium we sometimes call a neutron star with such a quark mattock or a quark star now neutrons are comprised of one up and two down quarks Kwak matter made of these quark types would need to be confined by incredible pressures to maintain stability outside the atomic nucleus so that probably rules out having an entire star made of this stuff unless the quark matter is also strange it may be the when you neutrons disintegrate under high pressure half of the down quarks are converted to strange quarks the result is strange matter to special type of quark matter it has three quack types instead of two and that means more particles can occupy the lowest quantum energy states it's as though the quarks trick their way around the poly exclusion principle by having some of them put on silly disguises this lower energy state means that strange matter may be the most stable form of matter in the universe more stable even than iron which is the most stable atomic nucleus a star made entirely of this stuff should be completely stable and if they exist they could exist forever we call these strange stars not content even with this level of weirdness physicists have proposed even more mad ideas for neutron star cause if the density is high enough the conditions of the core may be so extreme that they resemble the time even before the quark epoch at less than a billionth of a second after the Big Bang the fundamental forces of nature were not as we know them today the electromagnetic force and the weak nuclear force were unified as the electroweak force it could be that neutron stars have an electro weak core an apple sized ball with the mass of two earths in which quarks themselves burn the outflowing energy is almost all in neutrinos and those may provide final pressure that halts the collapse of some stars into a black hole at least for another million years or so okay this is fun stuff and it keeps theoretical physicists off the streets but can we test any of this madness well yes have we maybe take the case of three c58 in the year 1181 chinese and japanese astronomers recorded a new star in the constellation of Cassiopeia it faded over six months but nearly one thousand years later after some small technological advancements we pointed our radio telescopes and then the orbiting Chandra x-ray Observatory to that spot and found a young pulsar a rapidly rotating neutron star 10,000 light-years distant now this wasn't so unexpected after all the Pulsar in the Crab Nebula was also observed as a supernova by chinese astronomers in 1054 except something was weird in the case of three see fifty eighths the x-ray data revealed a surface temperature of a mere million Kelvin much cooler than expected for a neutron star of its age a possible explanation is that a quark matter core formed at the heart of this neutron star and is slowly transforming into strange matter as down quarks flip into the more massive strange quarks they have to absorb energy from somewhere to provide for that extra mass that energy would be the heat energy of the neutron star there are other candidates that could be quark and or strange styles some appear a little bit too small for their mass suggesting quark matter densities then there are supernovae that appear way too bright and last too long and it's been hypothesized that these may be due to a second explosion as the neutron star collapses further into a quark star even the famous supernova that exploded in the Large Magellanic Cloud in 1987 has been hypothesized to have left behind a quark star the dying star shouldn't have been massive enough to leave a black hole yet astronomers still haven't found the expected neutron star at the location of the supernova nothing is confirmed yet but there are tantalizing hints that these exotic stars these monsters in the math may be very real who knows what other strange denizens look and yet to be discovered laws of physics and who knows which are actually out there waiting to be discovered in the expanse of space-time hey guys two