Facts about Interstellar Medium

1. 05

   Radio observations of the interstellar medium reveal a warm neutral phase dominated by atomic hydrogen that emits at a characteristic wavelength of 21 centimeters.

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2. 04

   Density in the interstellar medium is extraordinarily low, averaging roughly one atom per cubic centimeter in diffuse regions.

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3. 03

   Ultraviolet radiation from hot stars ionizes hydrogen in the interstellar medium, creating glowing regions known as HII regions.

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4. 02

   Vast regions of the interstellar medium exist as cold, dense molecular clouds where temperatures can drop as low as 10 Kelvin.

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5. 01

   The interstellar medium consists mostly of hydrogen and helium, with trace amounts of dust, cosmic rays, and magnetic fields filling the space between stars.

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