hydrogen-alpha
UK[ˈhaɪdrədʒən ˈælfə]US[ˈhaɪdrədʒən ˈælfə]
n
A specific deep-red spectral line of hydrogen, with a wavelength of 656.28 nanometers, produced by an electron transition in the hydrogen atom.
n
The emission or absorption of light at this wavelength, used in astronomy to observe features like solar prominences and the structure of nebulae.
Morpheme Breakdown
hydrogen
alpha
hydrogen
element
alpha
first
Etymology
The term is a modern scientific compound, directly combining the name of the element 'hydrogen' with the designation 'alpha'. 'Hydrogen' itself originates from Greek roots meaning "water-producer," coined because it produces water when burned in oxygen. 'Alpha' was adopted into scientific nomenclature from the Greek alphabet to signify the primary or first in a series. In astrophysics, the hydrogen-alpha line is the first and most intense line in the Balmer series of hydrogen's visible spectrum, its name logically reflecting its primacy for observing celestial hydrogen.
Analysis
Structure: hydrogen (element) + alpha (first)
- hydrogen: From French hydrogène, from Greek hydōr (water) + -genēs (born, produced). The functional role is to specify the chemical element.
- alpha: From Greek alpha, the first letter of the Greek alphabet. Its functional role is to denote the first (and most prominent) line in a spectral series.
Examples
Astronomers use hydrogen-alpha filters to capture detailed images of the Sun's chromosphere.
The vibrant red glow of the Orion Nebula is largely due to hydrogen-alpha emission.
The study focused on the Doppler shift of the hydrogen-alpha line to measure the star's radial velocity.