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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 ...
More discoveries followed, with water emission in 1969, methanol emission in 1970, and silicon monoxide emission in 1974, all emanating from within molecular clouds. These were termed masers , as from their narrow line widths and high effective temperatures it became clear that these sources were amplifying microwave radiation.
Real objects never behave as full-ideal black bodies, and instead the emitted radiation at a given frequency is a fraction of what the ideal emission would be. The emissivity of a material specifies how well a real body radiates energy as compared with a black body. This emissivity depends on factors such as temperature, emission angle, and ...
An ideal black body in thermal equilibrium has two main properties: [2] It is an ideal emitter: at every frequency, it emits as much or more thermal radiative energy as any other body at the same temperature. It is a diffuse emitter: measured per unit area perpendicular to the direction, the energy is radiated isotropically, independent of ...
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.
The X-ray continuum can arise from bremsstrahlung, either magnetic or ordinary Coulomb, black-body radiation, synchrotron radiation, inverse Compton scattering of lower-energy photons by relativistic electrons, knock-on collisions of fast protons with atomic electrons, and atomic recombination, with or without additional electron transitions.
Astronomers used the Hubble Space Telescope to make a landmark discovery of water vapor in the atmosphere of a planet just twice Earth’s diameter in size.
When energy is deposited in air, the air molecules become excited. As air is composed primarily of nitrogen and oxygen, excited N 2 and O 2 molecules are produced. These can react with other molecules, forming mainly ozone and nitrogen(II) oxide. Water vapor, when present, may also play a role; its presence is characterized by the hydrogen ...