midterm Flashcards
what is correct order of stellar spectral types from coolest to hottest?
MKGFABO
what is the order of the electromagnetic in order of increasing wavelength
GXUVIMR
gamma ray, x-ray, ultraviolet, visible, infrared, microwave, radio
according to the general theory of relativity, the presence of mass
causes a curvature (or warping) of spacetime
from einstein’s theory of general relativity, which of the follow occurs near a massive object, for instance near the event horizon of a black hole
time slows down, light emitted, spacetime is curved ALL OF THE ABOVE
in the sun suddenly collapsed to become a black hole, what would happen to the earth’s orbti
earth would keep orbiting as it currently does
einstein’s general theory of relativity describes gravity as
distortion of 4 dimensional spacetime
once a black hole forms, the size of the event horizon is determined only by
the mass of the black hole
region around a black hole within which everything is trapped and nothing can get out to interact with the rest of the universe
event horizon
first direct detection of gravitiational waves by ligo in 2015, the waves came from
the merger of two black holes
the effect that prevents a neutron star from collapsing even further into a black hole is called
neutron degeneracy pressue
which are two possible end states of a high-mass star after its supernova explosion
neutron star or black hole
why do we think there is a supermassive black hole at the center of our milky way galaxy
we see stars orbiting the center of the milky way galaxy with extreme speeds
you measure the object’s mass to be 8.5 m so you deduce that the unknown object is
a black hole
what happens for an object that approaches the event horizon of a black hole
time slows down
even though we can’t see it, how do we know that the x-ray binary system cygnus x-1 has a black hole
mass of the invisible object is too big to be a neutron star
which of the following is true about black hole
black holes can be formed as the remnants of massive stars after a supernova explosion
what is true about stellar corpses
black hole can form from a neutron star that exceeds 3 solar masses
what happens to the radius of the event horizon as material falls into a black hole
increases
where do we have strong evidence for the presence of a black hole
at the center of our milky way galaxy
how do we measure the mass of a black hole in an x-ray binary system
with the orbital period and velocities inferred from the doppler shift
what is the smallest in size (radius)
neutron stars
supernova 1987a emitted neurons that signified the formation of a neutron star
SN 1987A could still have left behind a neutron star
how do massive stars enrich the interstellar medium for subsequent generations of stars and planets
massive stars evolve quickly compared to low-mass stars, releasing a lot of material containing helium and heavier elements
what happens to a white dwarf it it accretes material from a binary companion and reaches the white dwarf
explodes as a white dwarf supernova
if you were looking at our solar system in 15 billion years
a white dwarf
white dwarf compared to a main sequence star with the same mass, would always be
smaller in radius
maximum possible mass for a white dwarf is 1.4 solar masses
chandrasekhar limit
why is it so difficult for astronomers to see new stars in the process of birth
star birth happens relatively quickly, most stars are born inside dusty clouds, protostars. ALL OF THE ABOVE
on an h-r diagram of a cluster of stars, which characteristic if the diagram do astronomers use as a good indicator of the cluster’s age
point on the main sequence where stars begin to “turn off”
when dies high-mass stop fusing new elements
after it created iron
life stages of high-mass stars
hydrogen core fusion (main sequence)
hydrogen shell burn
helium core fusion
the rapid onset of helium fusion in the core of a low-mass star is called
helium flash
how do massive stars enrich the interstellar medium for subsequent generations of stars and planets
massive stars evolve quickly compared to low-mass stars, releasing a lot of material
gravity vs pressure
Core pressure and temperature of a higher-mass star need to be larger in order to balance gravity
Gravity can create stars only if it can overcome the force of thermal pressure in a cloud
Thermal pressure- high temperatures cause particles to move around creating an outward pressure that counteracts gravity
what stellar quantities could be on the axes on the Hertzsprung-Russell diagram
surface temp and luminosity
in which part of the h-r diagram do the stars have the largest radius
upper right (low temp, high luminosity)
a star whose temp is increasing but who luminosity is roughly constant moves in what direction on the h-r diagram
to the left on the h-r diagram
most of the stars (90%) on a h-r diagram are found in a region called
main sequence
we see a star cluster where stars just like the sun are starting to leave the main sequence, how old is the star cluster
10 billion years old
based on the h-r digram of different star clusters, which of these star clusters is the older
M67
which of the following plots would be most similar to the h-r diagram of the clust
apparent brightness (y-axis) vs. color (x-axis)
which of these stars has the hottest temperature
an o star
what info would we need to measure a star’s luminosity
apparent brightness and distance
why does 10 solar mass star have a shorter main sequence lifetime than a 1 solar mass star
the 10 solar mass star has a much high luminosity
2 stars have the same luminosity but star b is 3 times farther away from earth than star a, compared to star a, star b will look
9 times fainter than star a
what is true about the sun
sun has the highest apparent brightness of all the stars we can see
what powers the sun’s tremendous luminosity
nuclear fusion of hydrogen into helium
how does the energy generated by nuclear fusion leave the sun’s core
mostly carried by photons
sun’s apparent path around the celestial sphere is cal
ecliptic
what is not true about the sun’s core
photons emanate from the core and mostly travel freely out of the sun
the star that provides energy for life on earth
the sun
what will happen to the sun when its in planetary nebula phase
decrease in mass by expelling its outer layers
on a blue sky sunny day, you briefly glance up at the sun, the part of the sun that you can see directly is called
photosphere
what can we learn from the doppler effect when observing stars
allows us to measure the star’s radial velocity (speed towards or away from us)
a star is observed to have an absorption line spectrum, what does that mean
absorbing light of certain wavelengths, corresponding to the various atomic elements in the star
how can we tell which elements a star is made of
each element has a unique absorption spectrum seen in the star’s light
how do we measure the mass of a star in a binary system
newton’s version of kepler’s third law, A generalization of Kepler’s third law used to calculate the masses of orbiting objects from measurements of orbital period and distance; written as
newton’s version of kepler’s 3rd law allows us to determine the masses of objects orbiting each other if we measure:
their period of revolution and the distance between them
kepler’s major breakthrough in understanding planetary motion came when he
explored elliptical orbits rather than just circular orbits
why is newton’s version of kepler’s 3rd law superior
newton’s version is more applicable, kepler’s version can be derived as a special case of newton’s version, newton dervied his version from fundamental laws of motion and gravity, ALL OF THE ABOVE
if the moon were twice as far as from the earth than it is, the force of gravity attracting the moon to the earth would be
25% (one-quarter) as strong
newton showed that to change the direction in which an object is moving,
one needs to apply a force
galileo’s observations of venus provided clear evidence in favor of the heliocentric model, what did he see?
galileo observed venus at all phases from crescent to full
newton’s 3rd law of motion
period square is distance cubed
p=orbital period in years
a= average distance from sun in AU
accurate statement about the copernican revolution
heliocentric model gives a simpler explanation for retrograde motion of the planets than the geocentric model
when it comes to our places in the solar system today, which model do we accept
heliocentric
a solar eclipse can only occur
during a new moon
sun’s apparent path around the celestial sphere is called
ecliptic
lets reduce the solar system by a factor of 10 billion, the sun is now the size of a large grapefuit (14 cm)
how big is the earth on this scale
size of a ball point
what is true about a crescent moon
a crescent moon will be relatively close to the direction of the sun
if the orbit of the moon was in the same plane as the ecliptic (orbital plane of the earth around the sun) roughly how many solar eclipses would we have each year
12
what scientific data from 1919 supported einstein’s theory of gravity over newton’s theory
observing starlight passing close to the sun during an eclipse
suppose the instead of 23.5, the earth’s tilt was 40 degree, how would this affect the seasons
the seasons would be more intense (colder winters, hotter summers)
how long is the first quarter moon to full moon
about one week
on our 1-to-10 billion scale, it’s just a half-mile walk to pluto, how far would you have to walk to reach alpha centauri
across the us to california
what would you have to change about the earth to stop our planet from having significantly different seasons
tilt of its axis
