Astro Quiz 4
The average density of the interstellar medium is
1 atom/cm^3
A type Ia supernova can be as luminous as
10 billions suns
A 10 M_SUN will evolve through the same phases as a...
20 M_SUN star
We observe neutral hydrogen gas using
21-cm emission
The sun will become a red giant star in about
5 billion years
_______ keeps the core of a red giant star from collapsing.
Degenerate pressure from electrons.
As a main-sequence star burns its core supply of hydrogen, what happens?
Helium builds up in the core
If a main-sequence star's core temperature increased, fusion reaction rates would _____ because the protons would be moving _____.
Increase; faster
What factor is most important in determining a stars position on the main sequence and its subsequent evolution?
Mass
What critical event transforms a protostar into a normal main-sequence star?
Nuclear Fusion begins in the core
What primarily makes it difficult to observe the process of star formation?
Star formation occurs in dusty regions
When radiation from an object passes through the interstellar medium
The object appears redder and dimmer
Dust in the ISM appears dark in _________ wavelengths and bright in _________ wavelengths.
Visible; infrared
As a protostar contracts,
either the luminosity decreases or the temperature increases
In a white dwarf, what is the source of pressure that halts its contraction as it cools.
electrons packed so closely that they become incompressible.
For an object in hydrostatic equilibrium, if the temperature inside the object were to increase, the object would.
expand
When looking at the space between stars, what are you most likely to see?
gas
Degenerate refers to a state of matter at
high density
Brown dwarfs are considered failed stars because
hydrogen fusion never begins in their cores
molecular hydrogen atoms can be found
in dense clouds where they are shielded from stellar radiation
As a protostar is evolving, its temperature
increases due to kinetic energy of infalling material.
An asymptotic giant branch star loses mass to the interstellar medium because
it has low surface gravity
Interstellar extinction refers to
light being absorbed by dust in interstellar space
A nova is the result of which explosive situation?
mass transfer onto a white dwarf
The ________ a main-sequence star is, the more hydrogen it has to burn, and the ______ its main-sequence lifetime.
more massive; shorter
Dust reddens starlight because it
preferentially affects light at visible and shorter wavelengths.
Molecular clouds, which have temperatures of around 10 K, are best observed at _____ wavelengths.
radio
What is a planetary nebula?
the ejected envelope of a giant star surrounding the remnant of a star
Stars evolve primarily because...
they use up the fuel in their cores.