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  2. Balmer series - Wikipedia

    en.wikipedia.org/wiki/Balmer_series

    The red H-alpha spectral line of the Balmer series of atomic hydrogen, which is the transition from the shell n = 3 to the shell n = 2, is one of the conspicuous colours of the universe. It contributes a bright red line to the spectra of emission or ionisation nebula, like the Orion Nebula , which are often H II regions found in star forming ...

  3. Interstellar medium - Wikipedia

    en.wikipedia.org/wiki/Interstellar_medium

    Interstellar dust grains re-emit the energy they absorb from starlight as quasi-blackbody emission in the far infrared, corresponding to typical dust grain temperatures of 20–100 K. Very small grains, essentially fragments of graphene bonded to hydrogen atoms around their edges (polycyclic aromatic hydrocarbons, PAHs), emit numerous spectral ...

  4. Hydrogen-alpha - Wikipedia

    en.wikipedia.org/wiki/Hydrogen-alpha

    Hydrogen-alpha, typically shortened to H-alpha or Hα, is a deep-red visible spectral line of the hydrogen atom with a wavelength of 656.28 nm in air and 656.46 nm in vacuum. It is the first spectral line in the Balmer series and is emitted when an electron falls from a hydrogen atom's third- to second-lowest energy level.

  5. Hydrogen - Wikipedia

    en.wikipedia.org/wiki/Hydrogen

    Inputs and outputs of the electrolysis of water production of hydrogen. Electrolysis of water is a conceptually simple method of producing hydrogen. 2 H 2 O(l) → 2 H 2 (g) + O 2 (g) Commercial electrolyzers use nickel-based catalysts in strongly alkaline solution. Platinum is a better catalyst but is expensive. [110]

  6. Interstellar cloud - Wikipedia

    en.wikipedia.org/wiki/Interstellar_cloud

    Reflection nebula IRAS 10082-5647 observed by the Hubble Space Telescope. These interstellar clouds possess a velocity higher than can be explained by the rotation of the Milky Way . [ 5 ] By definition, these clouds must have a v lsr greater than 90 km s −1 , where v lsr is the local standard rest velocity.

  7. Hydrogen spectral series - Wikipedia

    en.wikipedia.org/wiki/Hydrogen_spectral_series

    The spectral series of hydrogen, on a logarithmic scale. The emission spectrum of atomic hydrogen has been divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two energy levels in an atom.

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  9. Molecular cloud - Wikipedia

    en.wikipedia.org/wiki/Molecular_cloud

    Hydrogen is the most abundant species of atom in molecular clouds, and under the right conditions it will form the H 2 molecule. Despite its abundance, the detection of H 2 proved difficult. Due to its symmetrical molecule, H 2 molecules have a weak rotational and vibrational modes, making it virtually invisible to direct observation.