Lyman-alpha emission

Definition

Lyman-alpha emission refers to a specific wavelength of ultraviolet light emitted by hydrogen atoms when their electrons transition from the second energy level to the first. This emission is significant in astrophysics, especially in the study of starburst galaxies, where intense star formation leads to abundant ionization of hydrogen and results in strong Lyman-alpha signals.

5 Must Know Facts For Your Next Test

1. Lyman-alpha emission occurs at a wavelength of 121.6 nm, which falls in the ultraviolet part of the electromagnetic spectrum.
2. In starburst galaxies, Lyman-alpha emission is produced as massive young stars emit high-energy radiation that ionizes surrounding hydrogen gas.
3. This emission can be used as a tracer for star formation activity, helping astronomers understand how rapidly new stars are forming in various galaxies.
4. Lyman-alpha photons can be absorbed and re-emitted by surrounding gas, leading to complex profiles in spectral observations that provide clues about the dynamics and conditions within starburst galaxies.
5. The study of Lyman-alpha emission contributes to our understanding of the reionization era in the early universe, as it helps trace the evolution of hydrogen in response to early star formation and galaxy formation.

Review Questions

• How does Lyman-alpha emission serve as an indicator of star formation within starburst galaxies?
  • Lyman-alpha emission is a direct result of ionized hydrogen surrounding massive young stars in starburst galaxies. When these stars emit high-energy ultraviolet radiation, it ionizes nearby hydrogen, causing it to emit Lyman-alpha photons as electrons transition between energy levels. The strength and characteristics of this emission provide astronomers with crucial information about the rate of star formation, allowing them to assess how quickly new stars are forming in these energetic environments.
• Discuss the role of Lyman-alpha emission in our understanding of the early universe and cosmic reionization.
  • Lyman-alpha emission is essential for understanding cosmic reionization because it traces the presence and behavior of hydrogen during this critical period. As stars formed and began to emit ultraviolet radiation, they ionized surrounding hydrogen gas, releasing Lyman-alpha photons. By studying these emissions from distant galaxies, astronomers can gain insights into how star formation contributed to reionizing the universe after the cosmic dark ages, revealing patterns of galaxy evolution and interactions during that time.
• Evaluate the significance of Lyman-alpha emission profiles in analyzing the physical conditions within starburst galaxies.
  • The profiles of Lyman-alpha emission are significant because they reflect the physical conditions present within starburst galaxies. Variations in the strength and shape of these profiles indicate factors such as gas density, velocity dispersion, and temperature. Analyzing these profiles allows astronomers to infer details about outflows, inflows, and interactions with surrounding materials. This evaluation helps build a comprehensive picture of the dynamic environments within starburst galaxies and their role in galactic evolution.

Related terms

Hydrogen Atom: The simplest atom, consisting of one proton and one electron, which plays a key role in the formation of stars and the chemistry of the universe.

Star Formation: The process by which dense regions within molecular clouds collapse under gravity to form stars, often accompanied by the release of energy and radiation.

Ionization: The process in which an atom or molecule gains or loses electrons, resulting in the formation of ions; this is particularly relevant in high-energy environments like starburst galaxies.