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Forget TMZ - Here on Space Time we have all the latest details on the dysfunctional, explosive relationships between the stars.

Let me tell you a tale of a pair of star-crossed … well, stars.

When our galaxy was a little younger there were two ordinary stars - perhaps not unlike our sun, and they danced together in binary orbit.

Romantic, right?

But any good romance is also a tragedy.

After a billion or so years, one star died.

It had burned brighter and faster, until it’s heart of fusing hydrogen shriveled into a dead core of carbon and oxygen.

Ejecting its outer layers, it became a searing hot, planet-sized orb of incredible density - a white dwarf.

And this is where the romantic tragedy turns into a horror story.

As the zombified stellar core and still-living companion spiraled closer together.

A stream dull, red gas now connected the two - the outer envelope of the star falling into the intense gravitational embrace of its old companion.

There, in the extreme surface gravity of the ultradense white dwarf, a layer of hydrogen built up.

At a critical point, that surface reached the temperature and pressure of a stellar core.

A storm of fusion ripped around the planet-sized white dwarf, spraying its atmosphere into space and for a couple of weeks shining 10s of thousands of times brighter.

Centuries later, on March 11, 1437, the light from that explosion swept past the Earth.

There, the royal astronomers of King Sejong’s court in Korea recorded a new point of light in the constellation of Wei, in what we call Scorpius.

They named it a guest star.

We now call this phenomenon a nova, from stella nova, or new star.

Romantic names, even if the stellar partnership is a disaster.

Our galaxy is full of these sorts of dysfunctional stellar relationships.

With more than half of all stars existing in binary orbits, it’s inevitable that many stellar remnants will end up in these parasitic spirals with their partners.

Today we’re going to look at the worst of these - from the novae produced by white dwarfs, to X-ray binaries created by neutron stars and black holes - and much weirder things besides.

These days, if you point one of our newfangled giant telescopes at the same spot where the royal Korean astronomers saw their guest star … you see nothing.

But if you pan a bit you find a puff of gas - a beautiful nebula, all that remains of that explosion.

Mysteriously, the ill-fated binary isn’t in the center of inside the nebula - it’s wandered a bit since 1437.

But it can be found if you look a little off center for a spot of light that flares erratically from visible to X-ray wavelengths.

It was Mike Shara Astrophysics Curator at the American Museum of Natural History, who figured all of this out.

After discovering the nebula from the 1437 nova back in the 80s, he spent decades tracking down the culprit system.

He finally identified a nearby flaring white dwarf binary - a so-called cataclysmic variable - and realized that it was the same object as a dwarf nova that he found on multiple old photographic places as far back as 1923.

A dwarf nova is what you think - it's like a regular nova, but much weaker.

They result when denser streams of matter hit the white dwarf and flare due to heat, but do not produce the storm of fusion of the classical nova.

But as Dr Shara discovered, it turns out that dwarf novae are just what classical nova do between those bigger explosions.

With observations of this dwarf nova spanning the last century, Shara could extrapolate its path back another half-millenium.

That placed it exactly where those royal astronomers saw their classical nova.

So cataclysmic variables must slowly build up their hydrogen layer, sputtering and flaring as they do so, until a critical temperature and pressure sends them over the edge.

After which they start the whole process all over again.

The system responsible for the 1437 nova is by no means unusual.

50 or so classical novae go off in our galaxy every year.

Cataclysmic variables do come in some variety - for example we have polars.

If the white dwarf has a strong magnetic field, the flow of gas from its companion is channeled by that field.

As charged particles spiral along the magnetic field lines they emit synchrotron radiation, and bright X-ray light is emitted as the gas hits the polar regions of the white dwarf - like a particularly violent auroras.

Cataclysmic variables are somewhat impressive, but for a real cataclysm it’s hard to go past an X-ray binary.

Just replace the white dwarf with a neutron star or black hole.

Those are what you get when the most massive stars die.

The remnant core now contracts to the point that atomic nuclei are no longer distinct - instead they meld together, protons and electrons combine to become neutrons, and you’re left with a ball of hyperdense matter the size of a city.

And its mass is high enough it sucks itself into a black hole.

This is all stuff we’ve talked about before - be we haven’t seen the effect on a hapless companion star of having one of these as its binary partner.

Once again, if the two are close enough, gas is syphoned from the star onto the black hole or neutron star.

If forms an accretion disk - and in X-ray binaries, it’s the accretion disk itself that glows bright.

That’s because the gravitational field of the compact object is so strong, falling gas reaches incredible speeds - which means incredible friction - which means heat and light.

They glow X-ray hot.

And like cataclysmic variables, the flow is uneven so the X-rays fluctuate.

In the case of neutron star X-ray binaries, that fluctuation includes powerful flares, resulting from denser clumps of material hitting the rapidly rotating surface of the neutron star.

Sometimes we also see the neutron star as a pulsar.

Its powerful magnetic field channels high energy particles into a jet that traces a circle across the sky - and often sweeping past the earth to produce metronome-precise pulses - most brightly in radio light, but potentially at all wavelengths.

Black hole x-ray binaries seem a bit more boring by comparison, because the black hole has no surface for the gas to fall onto - so no x-ray flares.

The nearest such system is the famous Cynus X1 X-ray binary, where a black hole the mass of 15 Suns is busy gorging on a blue giant star.

As with cataclysmic variables, X-ray binaries are relatively common - we know of 100s in the Milky Way.

But there are some much rarer, and, frankly, more awful manifestations of this phenomenon.

Take the black widow.

This is almost as cool a detective story as the 1437 nova.

To start, you need to know that when you look at our galaxy in gamma rays - the highest energy light there is - the brightest points you see are pulsars, and those gamma ray spots are pretty much always accompanied by the classic metronome-precise pulses of radio light.

Except of course when they’re not.

And there are a handful of mysteriously pulse-free gamma ray sources that otherwise look like they should be pulsars.

It was Roger Romani of Stanford who figured this one out.

He observed these objects using visible wavelength of light - and found one object was indeed pulsing.

But the pulses were far too slow - it brightened and dimmed avery … hours, while pulsars flash on the scale of seconds, or even microseconds.

The source also become bluer as it brightened, redder as it faded.

Well it turns out this object is a pulsar, and it’s in orbit around a companion star - in this case a brown dwarf, which is a star not quite massive enough to generate its own energy by nuclear fusion.

In this case the companion didn’t start out as a brown dwarf - it became one after losing most of its mass to its ravenous partner.

That brown dwarf orbits perilously close to the neutron star.

The neutron star’s jets sweep it hundreds of times per second, slowly blasting away its gas.

That gas forms an enveloping ring around the whole system, which then falls onto the neutron star.

The same gas blocks any radio light, but allows the more penetrating gamma ray light to pass through.

And the pulsing of visible light?

Well that’s when the super-heated “daytime” side of the brown dwarf comes into our view, while the red, dim phase is when we are looking at its night side.

This object became known as the black widow, and with the discovery of several similar systems, black widow is now the name of the object class.

Sticking with the deadly spider motif, if that second star is a red dwarf we have a red back.

That second star is doomed to an ignominious end.

First its whittled away until its not a star any more, and eventually we expect it to become to become more and more Jupiter-like and then just an icy core.

Finally that core is expected to break up in the neutron star’s tidal field and be scattered into the void.

On the other hand cataclysmic variables - like the one that produced the 1437 nova - have a more impressive end to look forward to.

The white dwarf in these systems builds up mass until releasing it as a nova.

But in that explosion it only ejects maybe 5% of the accreted material.

The rest stays with the white dwarf, which slowly grows in mass.

Eventually, the core of the white dwarf reaches a temperature of hundred of millions of Kelvin, and the star’s carbon and oxygen can begin to fuse.

A runaway fusion reaction rips through the star, which explodes as a Type 1 supernova.

Those supernovae are visible not just across the galaxy, but in galaxies across the universe.

To them, they were the explosives ends to long and fiery relationships, but to us they seem a little petulant.

Like the final slamming of doors from distant parts of spacetime.