AST EXAM 3 Flashcards
what two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
gravitational force and outward gas pressure
T/F: nuclear power plants on earth create energy in the same way as the sun
false
from center outward, which of the following lists the layers of the sun in the correct order
core, radiation zone, convection zone, photosphere, chromosphere, corona
why do sunspots appear dark?
they are regions that are significantly cooler than the rest of the photosphere
the sun has enough nuclear fuel to last for another
5 billion years
suppose you try to bring two protons close together, because of the electromagnetic force, the two protons will
repel on another
what is the approx temp of the sun’s core
15 million K
the star Alpha Centauri A is the same type of star as the sun, but its luminosity is about 1.6 times that of the sun, what can we conclude
ACA fuses hydrogen into helium in its core at a higher rate than our sun
approximately, what is the sun made of
70% H, 28% HE, 2% other elements
based on its surface temp of 6,000K, most photons that leave the sun’s surface lie in which region of the electromagnetic spectrum
visible
true or false: the corona and chromosphere are hotter than the photosphere
true
what is the solar wind
a stream of charged particles flowing outward from the surface of the sun
which of the following is the phase of matter in the interior of the sun
plasma
if the suns surface cooled, how would its appearance change
it would appear more red
the suns surface is called the
photosphere
true or false: the sun rotates more quickly at the equator than at the poles
true
by what process does the sun generate energy
nuclear fusion
what happens to energy in the sun’s convection zone
energy is transported outward by the rising of hot plasma
if star A is closer to us that Star B, then star A’s parallax angle is
larger than that of Star B
the spectral sequence sorts stars according to
surface temps
the faintest star visible to the naked eye has an apparent magnitude of about
6
star A has a absolute magnitude of 3, and star B has an absolute magnitude of 5, which star is brighter in our sky
there is not enough info to answer the question
which of the following is the most numerous type of main-sequence star
an M star
which of the following stars has a spectrum that peaks at the shortest wavelength
a blue star
which of the following best describes the axes of a Hertzsprung-russel disgram
surface temperature on the horizontal axis and luminosity on the vertical axis
ten parsecs is about
32.6 light-years
on a H-R diagram, stellar radii
increase diagonally from the lower left to the upper right
the total amount of power that a star radiated into space is called its
luminosity
the stellar spectral sequence, in order of decreasing temperatures is
OBAFGKM
which star is the hottest star
O
which of the following luminosity classes refers to stars on the main sequence
V
on a H-R diagram, where would you find stars that are cool and luminous
upper right
on a main sequence ,stars obtain their energy
by converting hydrogen to helium
you observe a star and you want to plot it on a H-R diagram, you will need to measure all of the following, except the star’s
mass
how is the lifetime of a star related to its mass
more massive stars live much shorter lives than less massive stars
which of the following statements about spectral types of stars is not generally true
the spectral type of a star can be used to determine its distance
The basic fusion reaction through which the Sun produces energy is __________.
Four hydrogen nuclei fuse to make one helium nucleus
The energy that is released in the hydrogen fusion reaction comes from __________.
The difference in mass between the four hydrogen nuclei and the single resulting helium nucleus
Place the layers of the Sun into the correct order from innermost at left to outermost at right.
Core, Radiation zone, convection zone, photosphere, chromosphere, corona
All the phenomena of solar activity — including sunspots, flares, coronal mass ejections, and the sunspot cycle — are tied to changes in the Sun’s __________.
magnetic field
Rank the layers of the Sun based on their density, from highest to lowest.
Core, radiation zone, convection zone, photosphere, chromosphere, corona
In which of the following layer(s) of the Sun does nuclear fusion occur?
core
What two items on the list below are in balance in what we call gravitational equilibrium?
gas pressure and gravity
To place a star on an H-R diagram, we must know its __________.
surface temp and luminosity
On the H-R diagram, most stars fall into the region labeled ____________.
main sequence
Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________.
cooler and larger in radius
Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________.
hotter and smaller in radius
what is the fate of an isolated brown dwarf
it will remain a brown dwarf forever
which of the following masses separates low mass stars from high mass stars
about 2 solar masses
how does the surface temp and luminosity of a protostar compare to the surface temp and luminosity of the main sequence star it becomes
a main sequence star is hotter and dimmer than it was as a protostar
what core temp is required before hydrogen fusion can begin in a star
Ten mil K
what is a protostar
a star that is still in the process of forming
what would happen if the sun was a black hole
NOTHING
what is the max mass of a white dwarf
1.4
max mass of a neutron star?
3
Stars that are fusing hydrogen in their cores are
main-sequence stars
what is a nova
The temperature of accreted matter eventually becomes
hot enough for hydrogen fusion. Fusion begins
suddenly and explosively
what is a massive star super nova
Iron core of a massive star reaches
white dwarf limit and collapses into a
neutron star, causing total explosion.
what is a white dwarf supernova
Carbon fusion suddenly begins as a white
dwarf in close binary system reaches
white dwarf limit, causing total explosion.
what is the mass of the sun
2 X 10 to the 30 kg
what is the rotation period of the sun
25 days
true or false: bigger stars are built faster than smaller stars
TRUE
what are sunspots
Are cooler than other parts of the Sun’s surface (4000 K) Are regions with strong magnetic fields
a neutron star is
the core remnant of a star that died in a massive star supernova
which of the following is closest in mass to a typical white dwarf
the sun
the minimum mass of a black hole that forms during a massive star supernova is roughly
3 solar masses
a white dwarf is mostly made of
carbon
what triggers a nova explosion
hydrogen gas from a companion star builds up on the surface of the white dwarf and when the temp gets high enough, it fuses to helium
true or false: our sun will likely undergo a nova event in about 5 billion years
false
true or false:the remnant left behind by a white-dwarf supernova is a neutron star
false
true or false: there is no upper limit to the mass of a neutron star
false
which of the following best describes a black hole
a place from which the escape velocity exceeds the speed of light
