lemme tell you about relativistic space fireballs.

yeah, you read that right.

space fireballs, or flashes that release as much energy in SECONDS as the Sun releases in its entire 10 billion yr life.

also known as: GAMMA RAY BURSTS.

some bursts are extremely short (less than a couple of seconds) and some are fairly long (several minutes). a few are even as long as a couple of hours.

what could possibly form such an energetic, bright, and powerful fireball careening through space?

we think that the short gamma ray bursts (<2sec) form from merging binary neutron stars or a black hole swallowing a neutron star. both neutron stars and black holes are the dead remnants of ~supernovae~!

neutron stars are incredibly small & highly dense: 1 tsp has a mass 900x the mass of a pyramid.

their structure is exotic: the crusts consist of electrons and a smattering of nuclei, but the core is "nuclear pasta" thought to be degenerate strange matter or a quark gluon plasma

when binary neutron stars merge, they produce a KiLoNoVaE.

shortly before the kilonova releases enough energy to form a gamma ray burst, they release short 'warning' flares that we think are the result of tidal forces.

tidal forces are forces stretching an object away from its center of mass. below is a gif of the tidal forces the moon exacts on the earth-- they create ocean currents and actually affect the Earth's temperature regulation!

in neutron-neutron star mergers, tidal forces between the nuclear pasta core and solid crust are periodic, meaning they follow a regular pattern.

it could be that at one particular frequency (mode), the tidal forces are SO powerful that they SHATTER the crust.

once the crust completely shatters, it emits built-up energy as precursor flares -- small, quick bursts of light that herald an imminent crescendo: the gamma ray burst.

longer gamma ray bursts (2sec - a couple hours) are thought to form from core-collapse supernovae or even more exotic phenomena like magnetars (a neutron star with an EXTREME magnetic field).

when extremely massive, highly rotating stars die, they collapse to form either a black hole or a magnetar.

matter surrounding the stellar core rains down but, rather than disappearing into the black hole/magnetar, it gets trapped by the rapid rotation & forms an accretion disk

the super dense accretion disk surrounds the dead core of the compact object (the black hole or the magnetar).

magnetic fields threading through these accretion disks get dragged along the disk's rotation, getting so tangled that the field lines tighten and launch jets.

these astrophysical jets, which consist of beams of photons and charged particles like electrons and protons, tear through the shells of the star and ultimately all the way through the stellar surface, beaming all the way out into space at distances up to one million parsecs.

so what causes the actual gamma ray burst *emission*?

this is where we get into some complicated physics, and frankly the answer isn't clear yet. but bear with me, because it's very cool stuff.

remember that light is waves, and that gamma rays are the MOST energetic waves on the entire electromagnetic spectrum. you can see below that gamma rays have the shortest wavelengths and highest frequencies of all types of electromagnetic radiation.

so the real question is: how do compact objects produce something SO energetic?

now we get into the cool physics part :)

remember E=mc^2? for something to have a high energy (E) we need extremely high velocities (c, the speed of light). high velocities are deemed "relativistic"

to get relativistic velocities, we think multiple shells of matter traveling at sliiiightly different speeds within the jets ram into each other, called internal shocks.

charged particles and photons ram into each other in the internal shocks, creating a soup of particles.

within the internal shocks, electrons are thought to get trapped on magnetic field lines, accelerating as they travel until they are ultra-relativistic electrons. then, they scatter off low energy photons, transferring energy to make them high energy photons.

in other words: magnetic fields, ultra-relativistic electrons, and scattering effects create extremely high energy photons aka GAMMA RAYS!

once the gamma ray burst subsides, it leaves behind an afterglow that covers the rest of the electromagnetic spectrum (X-ray, UV, optical, infrared, and radio).

this is detectable for days afterwards.

gamma ray burst jets are highly beamed, meaning they are extremely narrow and highly collimated. that means that they are extreeeemely unlikely to hit the Earth, especially because all gamma ray bursts detected to date are outside of the Milky Way.

that said, if there was a gamma ray burst inside of the Milky Way and pointed towards Earth, it would be extremely bad juju.