Chapter 11 Flashcards
What are the main constituents of interstellar gas?
Hydrogen and Helium
What type of nebula contains stars of spectral types O and B?
An emission Nebula
What causes the blue color associated with reflection nebulae?
The reflection nebulae is a cloud of dust. When light from a star encounters this cloud, the short wavelength blue light “bounces back” from the cloud towards us, and the longer wavelength re light passes through.
What is the source of the 21-centimeter radiation coming from a cloud of interstellar matter?
Electrons in individual hydrogen atoms flipping their intrinsic spin states from being parallel to being anti parallel to that of their parent protons
Which of the following are not the effects we experience from Dark dust clouds in space?
A. Dust clouds absorb starlight and re-emit it as invisible ultraviolet radiation.
B. Carbon monoxide molecules in dust clouds give off radio waves.
C. Dust Clouds dim starlight.
D. Dust clouds redden starlight.
A and D
What temperature is required to initiate nuclear fusion in a stellar core?
10,000,000 K
Why does star formation require a “triggering” event?
Atoms are too small and far apart for Gravity to overrule their individual motions and bring them together.
What is the meaning of zero-age main sequence?
It is the band on the H-R diagram in which stars are arranged as they begin their extended period of stable nuclear fusion.
What are brown dwarfs?
Low-mass object that never became stars
Failed stars with too little mass to fuse hydrogen.
Why do star clusters provide excellent tests for theories of stellar evolution?
The stars in any particular cluster formed at roughly the same time from the same primary material and under the same environmental conditions.
What are globular clusters?
They contain from hundreds of thousands to millions of stars and have a typical size of about 50 parsecs.
(Stars in globular clusters are tightly packed)
The main difference between the Pleiades cluster and Omega Centauri is that the Pleiades cluster is much….
Younger
As a star moves from stage 6 to stage 7 it becomes…
Hotter and smaller
The Rho Ophiuchi cloud (Dark Dust Cloud), is dark because…
Starlight from behind the cloud does not penetrate the cloud.
What is true about interstellar medium?
We know more about the gas than he dust.
