Galactic multiwavelength astronomy combines spectral bands that respond differently to stars, gas, dust, magnetic fields, temperature, and energetic particles.
Interstellar grains heated by starlight emit a modified blackbody spectrum, with a frequency-dependent emissivity multiplying the Planck law. This Galactic thermal dust emission rises across much of the microwave/submillimeter band and contaminates high-frequency cosmic microwave background measurements. Its strength and effective emissivity vary across the sky, so the frequency at which it exceeds cosmological anisotropy is not a universal constant.
Galactic synchrotron emission is nonthermal radio radiation from relativistic electrons spiralling in the Galactic magnetic field. Its broad latitude distribution reflects cosmic-ray transport and the magnetic halo.
Diffuse Galactic gamma rays arise mainly from neutral-pion decay after cosmic-ray nuclear collisions, electron bremsstrahlung in gas, and inverse-Compton scattering from radiation fields.
The Galactic scale height measures the vertical thickness of a tracer. Gravity, velocity dispersion, thermal pressure, magnetic and cosmic-ray support, particle transport, and source lifetime determine its value.
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