Chapter 15 Flashcards
What is the gas and dust that fill the space between the stars within a galaxy?
Interstellar medium
The evolution of a star depends on what?
Mass
What are small particles or grains of matter distributed throughout interstellar space?
Interstellar dust
What is the dimming of visible and ultraviolet light by interstellar dust?
Interstellar extinction
What is the effect by which stars and other objects, when viewed through interstellar dust, appear redder than they actually are?
Interstellar reddening
What is a discrete, high-density region of the interstellar medium made up mostly of atomic or molecular hydrogen and dust?
Interstellar cloud
What is a low-density region of the interstellar medium that fills the space between interstellar clouds?
Intercloud gas
What are the four components of the interstellar medium?
- Hot intercloud gas
- Warm intercloud gas
- Cold intercloud gas
- Interstellar gas
What is a nebula?
It is any interstellar cloud of gas & dust
Do long wavelengths or short wavelengths penetrate interstellar dust?
Long wavelengths
What is an interstellar cloud composed primarily of molecular hydrogen?
Molecular cloud
What is a very young object that is still contracting before becoming a true star?
Protostar
What is a reflection nebula?
Its the scattered light that shows a blue color around bright stars
What is an emission nebula?
Its a cloud of interstellar gas and dust that emits lights in different colors
What is a cold dark nebula?
Its a nebula that it blocks visible light that is emitted from stars behind it
What are planetary nebula?
They are the ejected envelopes from dying stars
What is meant by the term - ZAMS?
Zero-Age Main Sequence
What is the Zero-Age Main Sequence?
It is where stars start hydrogen fusion
What is a star cluster?
It’s a group of stars that all formed at the same time and in the same general location
Why is understanding the interstellar medium important?
It helps us to understand the creation of the universe
What is a proto-planetary disk?
It’s a rotating ring-shaped disk of dense gas and dust that surrounds a newly formed star
(It look like Target’s logo)
What does the H-R diagram for a young star cluster look like?
A lot of the stars are still forming, so only a few are on the main sequence while the rest are below it
(Look at Chapter 15 slide 58 for visual)
What does the H-R diagram for a middle-aged star cluster look like?
All the low mass stars have become main sequence stars, so the majority of them are on the main sequence while a few are above it
(Look at Chapter 15 slide 59 for visual)
What does the H-R diagram for an old star cluster look like?
A lot of the stars have stopped producing hydrogen in their core, so the majority of them have become red giants/supergiants and are above the main sequence. Only a few remain on the main sequence
(Look at Chapter 15 slide 60 for visual)
How does the pre-main sequence evolutionary track of a low-mass star differ from the track of a high-mass star?
Since a high-mass star is massive it won’t take long for it’s core to start burning hydrogen. This means that it’s evolutionary track will look like a horizontal line at the top of the diagram. It takes a while for a low-mass star to burn hydrogen, so it will go down until it starts to burn hydrogen. Once that happens it will stop going down and it will move to the left until it reaches the main sequence.
(Look at Chapter 15 slide 52 fro visual)
An H I region is a region of what?
Atomic hydrogen
proton + electron
An H II region is a region of what?
Ionized hydrogen
just proton, no electron
An H2 region is a region of what?
Molecular hydrogen
two atoms of hydrogen
What are the pre-main sequence stages to form a star?
- A molecular cloud loses its equilibrium
- The denser regions in the cloud start to collapse
- As it’s collapsing the regions are becoming hotter and smaller
- They then turn into dense, star-forming cores
What causes a cloud to lose its equilibrium and start to contract?
Gravity
True or False:
Some regions inside a molecular cloud are denser than others
True
