Astronomers observe spectra of planetary nebulae to learn about the stars that created them, and to understand how planetary nebulae contribute to the chemical enrichment of the Milky Way Galaxy over time. In order to determine the chemical abundances in nebulae, astronomers need to know the temperature of the gas and its density. Sulfur emission lines are useful for determining density in planetary nebulae. Certain electron transitions involve energy levels that are said to be metastable; the resulting emission lines are called "forbidden" lines, which really only means that they are less likely to occur than emission lines from the ordinary kind of transitions. lons and electrons in a planetary nebula are always moving and bumping into each other. The energy exchanged in these collisions isn't enough to strip off electrons, but it is enough to kick an electron to a higher energy level within the ground state. In fact, the only way that these higher levels can be populated is by collisions; their forbidden nature makes it extremely unlikely for an upward transition to be produced by an absorbed photon. In order to return to ground state, a photon must be released. One such wavelengths of interest is 673.1 nm (in the very red part of the visible spectrum). The λ 673.1 nm line strengthens as the nebulae gas density increases because such collisions also increase with density. 1. What is the frequency of that line? 2. What is the energy of that line? 3. Is a transition that takes place in the microwave region of the EM spectrum, which is capable of cooking food, higher or lower energy than the previously mentioned electron transition in S?
Astronomers observe spectra of planetary nebulae to learn about the stars that created them, and to understand how planetary nebulae contribute to the chemical enrichment of the Milky Way Galaxy over time. In order to determine the chemical abundances in nebulae, astronomers need to know the temperature of the gas and its density. Sulfur emission lines are useful for determining density in planetary nebulae. Certain electron transitions involve energy levels that are said to be metastable; the resulting emission lines are called "forbidden" lines, which really only means that they are less likely to occur than emission lines from the ordinary kind of transitions. lons and electrons in a planetary nebula are always moving and bumping into each other. The energy exchanged in these collisions isn't enough to strip off electrons, but it is enough to kick an electron to a higher energy level within the ground state. In fact, the only way that these higher levels can be populated is by collisions; their forbidden nature makes it extremely unlikely for an upward transition to be produced by an absorbed photon. In order to return to ground state, a photon must be released. One such wavelengths of interest is 673.1 nm (in the very red part of the visible spectrum). The λ 673.1 nm line strengthens as the nebulae gas density increases because such collisions also increase with density. 1. What is the frequency of that line? 2. What is the energy of that line? 3. Is a transition that takes place in the microwave region of the EM spectrum, which is capable of cooking food, higher or lower energy than the previously mentioned electron transition in S?
ChapterU5: Fire: Energy , Thermodynamics, And Oxidation-reduction
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Transcribed Image Text:**Understanding Planetary Nebulae through Spectra Analysis**
Astronomers study the spectra of planetary nebulae to gain insights into the stars that created them. This research helps understand the chemical enrichment of the Milky Way Galaxy over time. To determine the chemical abundances in nebulae, astronomers must know the temperature and density of the gas. Sulfur emission lines are particularly useful for determining density in planetary nebulae.
Some electron transitions involve metastable energy levels. The resulting emission lines are known as "forbidden" lines, meaning they occur less frequently than those from ordinary transitions.
In a planetary nebula, ions and electrons are in constant motion, colliding with each other. These collisions usually don't strip electrons but can elevate an electron to a higher energy level within the ground state. Collisions are the primary means of populating these higher levels due to their forbidden nature, which makes upward transitions from an absorbed photon improbable.
To return to ground state, a photon must be released. A notable wavelength is 673.1 nm, located in the very red part of the visible spectrum. The strength of the 673.1 nm line grows with nebulae gas density as collisions increase with density.
**Questions for Further Exploration:**
1. **What is the frequency of that line?**
___________________________
2. **What is the energy of that line?**
___________________________
3. **Is a transition in the microwave region of the EM spectrum, capable of cooking food, higher or lower in energy than the previously mentioned electron transition in S?**
_______________
Expert Solution
Step 1: Spectra of nebulae
The spectra of planetary nebulae are fundamentally different from those of stars. Instead of a continuous color from red to blue as in the case of the Sun, the spectra of planetary nebulae are dominated by discrete emission lines emitted by atoms and ions.
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