Interstellar Medium and Nebulae

Flashcards covering key vocabulary related to the interstellar medium and different types of nebulae, including their composition and appearance.

Interstellar Medium (ISM)

Composed of gas and dust located in the regions between the stars; roughly 75% Hydrogen, 25% Helium for gas, and microscopic carbon and silicates for dust.

Gas (in ISM)

Roughly 75% Hydrogen and 25% Helium, with trace amounts of metals.

Dust (in ISM)

Microscopic (10^-6 meters) in size, composed mostly of carbon and silicates.

Metals (in astronomy)

Any element other than hydrogen and helium.

Nebula

An enormous cloud of dust and gas occupying the space between stars, often acting as a nursery for new stars.

Dark Nebula

A cloud that is dense enough to block background light, appearing dark due to obscured visible light.

Emission Nebula

A cloud that is ionized by nearby hot stars (hotter than 25,000 K) and emits an emission spectrum, typically appearing reddish-pink due to hydrogen Balmer-line emission.

H II Region

Another name for an emission nebula, referring to ionized hydrogen (hydrogen with its electron stripped away).

Reflection Nebula

A cloud that scatters light from nearby cooler stars, appearing blue because dust scatters blue light more than red light.