Use these questions to test your understanding. If you get them wrong, you will be linked back to the relevant part of the notes.
Be sure you study them thoroughly (don't just get a quick fix for your mistake) so your overall understanding is improved.
1. The gas in an HI region is comprised of
a. hydrogen gas with electrons in the ground state b. ionized hydrogen gas
2. A molecular cloud is
a. a large, cold, dense collection of interstellar gas and dust
b. interstellar dust that is lit up by a nearby star and scatters some of the light toward us
c. an interstellar cloud made purely of complex molecules, mostly containing carbon
d. a region where a very hot star is ionizing the nearby gas
3. A newly formed massive, hot star changes the surrounding interstellar gas into
b. a glowing cloud of excited gas called an HII region
c. a dark globule seen as a shadow against the background light
4. Interstellar dust makes the things behind it look
d. it blots them out completely
5. A "reflection nebula" is
a. a cloud of interstellar grains aligned to reflect light similarly to a mirror
c. a cloud of interstellar material that lets look into regions we cannot see directly
d. an interstellar cloud that absorbs energy from nearby stars and emits it in the infrared
e. an interstellar cloud that is lit up by scattering light toward us from a star near the cloud
6. An HII region can be identified from