Question 1

The Pleiades show the characteristic blue color of ___________________ .&#10;A) a reflection nebula&#10;B) an emission nebula&#10;C) a dark nebula&#10;D) an HII region

Accepted Answer

The Pleiades star cluster is known for its characteristic blue color primarily because of the reflection nebula surrounding its stars. The dust in the reflection nebula scatters the blue light from the stars more than the red light, giving the nebula its distinctive blue hue. This is similar to the way Earth's atmosphere scatters sunlight, making the sky appear blue.

Question 2

Cold hydrogen gas produces ____ electromagnetic radiation by its spin flip.&#10;A) 21 m&#10;B) 21 mm&#10;C) 21 cm&#10;D) 21 km

Accepted Answer

Cold hydrogen gas produces 21 cm electromagnetic radiation due to the spin flip transition of its electron. This is a fundamental observation in radio astronomy, particularly for studying the interstellar medium.

Question 3

When light travels through thick dust and gas and all visible light is stopped, this is known as _____.&#10;A) reddening&#10;B) bluing&#10;C) extinction&#10;D) absorption

Accepted Answer

Extinction occurs when light travels through thick dust and gas, causing all visible light to be stopped or significantly dimmed. This effect is due to the scattering and absorption of light by the particles in the medium it is passing through, leading to a decrease in the intensity of light that reaches the observer.

Question 4

As light travels through dense gas, the gas scatters the blue waves and the light slowly ______.&#10;A) blues&#10;B) X-rays&#10;C) reddens&#10;D) shortens

Accepted Answer

As light travels through dense gas, the blue waves are scattered more than the other colors due to their shorter wavelength, making the light appear redder. This phenomenon is known as Rayleigh scattering.

Question 5

Gas and dust between the stars is called the ____.

Accepted Answer

The answer of Gas and dust between the stars is...

Question 6

_______________ occurs when material near the star cast shadows on gas farther away.

Accepted Answer

The answer of _______________ occurs when material near the star...

Question 7

An HII region is cold hydrogen.

Accepted Answer

An HII region is a cloud of glowing gas and plasma, primarily composed of ionized hydrogen, which is significantly hotter than the cold hydrogen found in HI regions.

Question 8

An HI region is ionized hydrogen.

Accepted Answer

An HI region contains neutral (not ionized) hydrogen atoms. HII regions are the ones that contain ionized hydrogen.

Deck 73: Gas and Dust in the Milky Way