What is the sun’s spectrum and how does it work?


What is the sun’s spectrum and how does it work?

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From my limited knowledge of physics:

All elements we know emit electromagnetic radiation, this radiation comes in the form of fotons that are formed when electrons in the atom go from a higher to a lower state of energy. Every element has its own spectrum, unique to it.

Knowing this, we can look at the light from a star, like the sun, and see what wavelengths the light has, and with that we can know what elements compose this star

Light is a spectrum of electromagnetic waves ranging in frequency from 400 to 700 nm for visible and around 1-1000 if you count X and IR rays. The sun can be estimated as something called a black body radiator, and a ssucj it has a peak in wavelength (i.e. one wavelength that is emmited more than all others) this is a result of characterise emmisions of the particles inside the body, depending on it’s heat. For our sun this is at about 500 nm.

Stars generate energy via a process known as nuclear fusion which emits energy as radiation across a wide spectrum of frequencies and heats up the core. The high temperatures of the core also cause matter within to emit radiation across a spectrum of frequencies.

All atoms are also independently capable of emitting radiation due to the constant absorption of radiation they experience, the energy from which needs to be reemitted to bring the atom back to its original states.

As fusion occurs in the core of the Sun, the wide range of frequencies of radiation emitted goes in all directions. Eventually this radiation reaches the atmosphere of the Sun, which contains mainly hydrogen and helium. These hydrogen and helium atoms then absorb the emitted radiation but may not reemit this radiation towards the Earth.

The resulting spectrum of the Sun, as seen from the Earth, then contains all of the frequencies emitted from the fusion process in the core, except for the specific frequencies absorbed by the Sun’s atmosphere.

Heated matter emits radiation. Most commonly as infrared radiation which we can’t see but can feel on our skin. When the heat exceeds a certain value, it starts glowing red. Keep heating up and it becomes yellow, then white, which means that all visible wavelengths are emitted – like a very hot piece of iron. Knowing this, we can attribute the heat to the colour of the light: 5500 degrees Kelvin is daylight “colored” (this light colour temperature is printed on light bulb boxes).

A perfectly black body would emit all wavelengths that come from this temperature. But atoms and molecules absorb very specific wavelengths. So while we know that a star of a certain temperature would emit a certain spectrum of so called blackbody radiation (which wouldn’t absorb any specific wavelength), we can observe that certain wavelengths are missing from the expected spectrum.

From the missing lines in the observed spectrum, we can deduce the presence of certain elements in a stars surface, which tells us a lot about that star.