Do emission nebula glow because of ionised or excited electrons?

In summary, emission nebulae glow due to the ionization of hydrogen atoms by ultraviolet radiation from massive stars, causing them to emit visible light as the electrons and nuclei recombine and drop to lower energy levels. This process includes transitions from higher to lower energy levels, resulting in the emission of photons, such as the H-alpha line. The electrons themselves do not emit light, but rather the atoms they are bound to. This understanding may be helpful in clarifying any confusion about the role of electrons in the glowing of emission nebulae.
  • #1
Nathi ORea
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TL;DR Summary
Do emission nebulae glow because of ionized electrons or excited ones?
I'm trying to figure out why emission nebulae glow.

I read various sites such as a NASA website explaining why they shine;

'The massive stars embedded within the nebula give off enormous amounts of ultraviolet radiation, ionizing the gas and causing it to shine.'

The Britanica article on emission nebula says;

'It was found that ultraviolet light from the star ionizes nearby hydrogen. The hydrogen atoms emit visible light after the electrons and nuclei recombine and the atoms drop to lower energy levels.'

My understanding is that we cannot see recombining ionised electrons in hydrogen, only those of the Balmer series which are only 'excited' electrons.

Wouldn't any electrons excited or ionized by UV simply reemmit emr in the ultraviolet again which we can't see?

Just fyi, I am just an astronomy enthusiast and real technical language and maths I probably won't get.

I'd appreciate any help
 
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  • #2
The electron often cascades downwards, transitioning from higher to lower energy levels like a ball bouncing down the stairs. From wiki's article on hydrogen alpha:

In the new atom, the electron may begin in any energy level, and subsequently cascades to the ground state (n = 1), emitting photons with each transition. Approximately half the time, this cascade will include the n = 3 to n = 2 transition and the atom will emit H-alpha light. Therefore, the H-alpha line occurs where hydrogen is being ionized.
 
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Greetings,
Nathi ORea said:
Summary:: Do emission nebulae glow because of ionized electrons or excited ones?

'It was found that ultraviolet light from the star ionizes nearby hydrogen. The hydrogen atoms emit visible light after the electrons and nuclei recombine and the atoms drop to lower energy levels.'
That is the correct physics. The gas is first ionized by the hot star. The resultant ion and a free electron recombine to form an atom in an excited electronic state. That excited state finally emits a photon as the excited atom decays to its ground state.

It appears that you are confused about a basic principle. The electrons do not emit light. The light is given off by an atom and the bound electron drops to a lower energy state.

This article from Scholarpedia may be of interest: Planetary nebulaeES
 
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  • #4
Drakkith said:
The electron often cascades downwards, transitioning from higher to lower energy levels like a ball bouncing down the stairs. From wiki's article on hydrogen alpha:

In the new atom, the electron may begin in any energy level, and subsequently cascades to the ground state (n = 1), emitting photons with each transition. Approximately half the time, this cascade will include the n = 3 to n = 2 transition and the atom will emit H-alpha light. Therefore, the H-alpha line occurs where hydrogen is being ionized.
Thanks so much. That makes sense!
I love the analogy of the ball bouncing down stairs!
thank you
 
  • #5
EigenState137 said:
Greetings,

That is the correct physics. The gas is first ionized by the hot star. The resultant ion and a free electron recombine to form an atom in an excited electronic state. That excited state finally emits a photon as the excited atom decays to its ground state.

It appears that you are confused about a basic principle. The electrons do not emit light. The light is given off by an atom and the bound electron drops to a lower energy state.

This article from Scholarpedia may be of interest: Planetary nebulaeES
Yes! Thank you!
I get it… the electron goes back to ground state (or I think n2 because of Balmer series) in stages.

Appreciate it
 

1. What is an emission nebula?

An emission nebula is a type of interstellar cloud of gas and dust that emits light in various colors. It is caused by the ionization of the gas particles, which creates a glowing effect.

2. How do emission nebulae glow?

Emission nebulae glow because of ionized or excited electrons. When high-energy particles, such as ultraviolet radiation, collide with the gas particles in the nebula, they cause the electrons to become excited and jump to higher energy levels. As the electrons return to their original energy levels, they release energy in the form of light, causing the nebula to glow.

3. What is the difference between ionized and excited electrons?

Ionized electrons have been stripped of their outermost electrons, leaving them with a positive charge. Excited electrons have absorbed energy and moved to a higher energy level, but they still have their original number of electrons and a neutral charge.

4. What types of gases are found in emission nebulae?

The most common gases found in emission nebulae are hydrogen, helium, and oxygen. These gases are easily ionized and emit light in different wavelengths, creating the colorful glow of the nebula.

5. How are emission nebulae formed?

Emission nebulae are formed when massive stars die and release large amounts of energy, including ultraviolet radiation. This radiation ionizes the surrounding gas, creating the glowing effect. The gas and dust in the nebula can also collapse under gravity, forming new stars and continuing the cycle of star formation.

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