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  2. Spectral line - Wikipedia

    en.wikipedia.org/wiki/Spectral_line

    A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules.

  3. Stellar classification - Wikipedia

    en.wikipedia.org/wiki/Stellar_classification

    [c] [11] Some of the most massive stars lie within this spectral class. O-type stars frequently have complicated surroundings that make measurement of their spectra difficult. O-type spectra formerly were defined by the ratio of the strength of the He II λ4541 relative to that of He I λ4471, where λ is the radiation wavelength. Spectral type ...

  4. Singlet state - Wikipedia

    en.wikipedia.org/wiki/Singlet_state

    In quantum mechanics, a singlet state usually refers to a system in which all electrons are paired. The term 'singlet' originally meant a linked set of particles whose net angular momentum is zero, that is, whose overall spin quantum number =. As a result, there is only one spectral line of a singlet state.

  5. Astronomical spectroscopy - Wikipedia

    en.wikipedia.org/wiki/Astronomical_spectroscopy

    The Star-Spectroscope of the Lick Observatory in 1898. Designed by James Keeler and constructed by John Brashear.. Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects.

  6. List of nearest stars by spectral type - Wikipedia

    en.wikipedia.org/wiki/List_of_nearest_stars_by...

    Below there are lists the nearest stars separated by spectral type. The scope of the list is still restricted to the main sequence spectral types: M, K, F, G, A, B and O. It may be later expanded to other types, such as S, D or C. The Alpha Centauri star system is the closest star system to the Sun.

  7. Zeeman effect - Wikipedia

    en.wikipedia.org/wiki/Zeeman_effect

    Zeeman effect on a sunspot spectral line George Ellery Hale was the first to notice the Zeeman effect in the solar spectra, indicating the existence of strong magnetic fields in sunspots. Such fields can be quite high, on the order of 0.1 tesla or higher.

  8. Equivalent width - Wikipedia

    en.wikipedia.org/wiki/Equivalent_width

    The equivalent width of a spectral line is a measure of the area of the line on a plot of intensity versus wavelength in relation to underlying continuum level. It is found by forming a rectangle with a height equal to that of continuum emission, and finding the width such that the area of the rectangle is equal to the area in the spectral line.

  9. V1429 Aquilae - Wikipedia

    en.wikipedia.org/wiki/V1429_Aquilae

    V1429 Aquilae is a single-lined spectroscopic binary.The existence of a companion is inferred from the highly periodic variations in the radial velocity of its spectral lines and by equally periodic variations in brightness and spectral line profiles.