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Rodot t1_ivjua01 wrote

It's black body radiation, usually taught in stat mech classes when deriving the Planck distribution (distribution of energies in a gas of photons). It's low level mechanism comes from what are called "continuum" interactions. They are called that because they produce a continuous spectrum unlike atomic interaction which are discrete.

Some examples of continuum interactions include Thomson/Compton scattering (photons bouncing off electrons, Thomson scattering is the low energy approximation and Compton is the relativistic case), Bremsstrahlung radiation (electrons scattering off ions), photoionization (electrons being kicked out of their atoms), collisional interactions (atoms and ions bumping into eachother), and autoionization (atoms with multiple excited electrons reconfiguring to shoot off an outer most electron through quantum tunneling). For those for who it's not clear where exactly the light comes from in all of these, accelerating charged particles emit light.

All of these interactions together create the Black-body (or Planck) distribution.

Source: I'm one of the developers of an astrophysical radiative transfer code


flyingpanda1018 t1_ivkifab wrote

Does the black body spectrum change for a neutron star, given there are significantly less electrons and protons than in normal matter?


Rodot t1_ivl46ap wrote

It's spectrum is much more complicated because it's very high energy and you need to consider how the light interests with the protons and the structure of the magnetic fields.


OfLittleToNoValue t1_ivmrwnd wrote

I'm not an astrophysicist, but are you saying electrons are moving so fast they generate light? Isn't light a photon? Where are they coming from?


Rodot t1_ivmvufb wrote

According to Maxwell's equations, a changing electric field creates a magnetic field, and a changing magnetic field creates an electric field. If you set this up as a set of differential equations you get perpendicular propagating waves in the electric and magnetic fields.

A charged particle moving at a constant speed makes a constant magnetic field. An accelerating charge makes a changing magnetic field which makes a changing electric field etc. which makes an electromagnet wave. The quantization of this field results in the waves propagating as photons.


OfLittleToNoValue t1_ivoeg6p wrote

But where do the photons come from?


Rodot t1_ivojlpk wrote

From the electromagnetic field


OfLittleToNoValue t1_ivoop6h wrote

They just poof into existence? I'm assuming I just don't understand what a photon actually is.


Rodot t1_ivopmiw wrote

Think of a photon as similar to a musical note when you play an instrument. For a string instrument, you pluck the string and it causes it to vibrate at a specific frequency depending on the length (i.e. it's boundary conditions). This is kind of like a photon but instead of plucking a string you are "plucking" the electromagnetic field and it makes a vibration at a certain frequency depending on the boundary conditions (electrons, ions, etc) of the system.


OfLittleToNoValue t1_ivorr0q wrote

I understand sound to be the consecutive vibration of atoms which is why sound cannot traverse a vacuum. For light to traverse space is my understanding that is that photos are some kind of discrete particle with mass and that's why things like solar sails work.

From what you're saying, the interaction of the fields creates photons. Is this energy converting into matter and the genesis of a discrete particle?


Rodot t1_ivorv7u wrote

Photons do not have mass. They do carry momentum though.


OfLittleToNoValue t1_ivosz7x wrote

Man I feel dumb. What is a photon made of then? It's just energy that flows and glows until it dissipates? Thanks for humoring my ignorance!


Rodot t1_ivqj6cx wrote

Photons are made of photons. They are fundamental particles


Bonesmash t1_ivm5n5j wrote

You got some good “how” replies. I just wanted to point out that when a neutron star is made, it’s an extremely energetic event, in addition to it having just been a nuclear fusion reactor. So that’s where the initial heat for the black body radiation came from.


KenHutchenson t1_ivkc7vj wrote

Wait whaaat!? Neutron stars don’t radiate photons!? Today I learned…that’s so cool.

So to see neutron stars do I need a special telescope?


8Eternity8 t1_ivkf3rt wrote

X-Rays are photons. Just with higher energy and outside the visible spectrum.

But yes you would need a special telescope to see something that only radiates in the x-ray spectrum.