astronomy 3
today we realize that the source of energy for the sun is a process called
nucelar fusion
The Sun is an enormous ball of gas. Left to itself, a ball of so many gas atoms should collapse under its own tremendous gravity. Why is our Sun not collapsing?
nuclear fusion in the core keeps the temperature and the pressure inside the sun at a high enough level so that gravity is balanced
a neutron star is as dense as
nucleus of an atom
what type of main sequence star is most likely to become a black hole?
o
which of the following statements about the mass of Sun during its lifetime is correct?
the sun will lose a significant amount of mass during and after its red giant phase
when stars become giants, which of the following does NOT usually happen?
their mass grows significantly as they incorproate planets and interstellar matter near the star
Order of the objects in the solar system
1 star (The Sun) 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) 5 dwarf planets (Pluto, Ceres, Haumea, Makemake, and Eris) 181 moons. 566,000 asteroids. 3,100 comets.
the first astronomer who did photometry in a systematic way (even though he did not have a telescope) was
Hipparchus
Where in the Sun does fusion of hydrogen occur?
Only in the core
einstein suggested that the regular change (advance) in the perihelion of the planet mercury could be explained by
a distortion in spacetime caused by the gravity of the sun
when astronomers discuss a nebula, what are they talking about?
a giant cloud of gas and dust between or among stars
according to the general theory of relativity, light and other radiation coming from a white dwarf or a neuron star should (and experiments show that it does) exists
a gravitational redshift
at the end of the p-p chain of nucelar fusion in the sun, hydrogen nuclei have been converted into
a helium nucleus
astronomers call a ball of matter that is contracting to become a star
a protostar
deep inside a black hole (and hidden from our view) is the compressed center, where all the "stuff" of the star goes. Astronomer call this central point
a singularity
which of the following looks the brightest in the sky?
a star with a magnitude -1
elements heavier than iron can be created during
a supernova explosion
from which of the following will a wave of light show the greatest gravitational redshift
a white dwarf
when a light wave leaves a region of strong gravity, compared to the same wave leaving a spaceship in empty space the wave in strong gravity will have
alll the characteristics are correct
the event in the life of a star that begins its expansion into a giant is
almost all of the hydrogen in its core that was hot enough for fusion has been turned into helium
the event in the life of a star that begins its expansion into a giant is
almost all the hydrogen in its core that was hot enough for fusion has been turned into helium
a star that is quite cool and has a very small radius compared to most stars is called
an M-type star
supposing we launched a very fast dart from the Space Shuttle, pointed in some direction away from any planet, so that it could travel beyond the solar system. What would it be most likely to hit first after traveling outward for a while?
an atom of interstellar gas
suppose each of the following objects could collapse into a black hole. each black hole would have a sphere around it that is the limit for escape--once you are inside this region, you cannot get away. for which object would this region be the largest in diameter
an entire galaxy of stars (with about a billions stars in it)
astronomers have concluded that growing supermassive black holes (which have millions of times the sun's mass or more) is pretty unlikely at our location in the milky way galaxy. where do they think is the most likely place in the milky way for such a supermassive black hole?
at the center of the milky way galaxy, where matter is more crowded
solar wind particles can be captured by the earths magnetosphere. when these particles spiral down along the magnetic field into the atmosphere, they are resopnsible for
aurorae (northern and southern lights)
why can a star with a mass like our sun NOT fuse(produce) further elements beyond carbon and oxygen?
because they just cannot get hot enough for the fusion of heavier nuclei
which color star is likely to be hottest?
blue and violet
today, astronomers can measure distances directly to worlds like Venus, Mars, the Moon, or satellites of Jupiter by
bouncing radar beams off them
stars that do not have what it takes to succeed as a star (i.e. do not have enough mass to fuse hydrogen into helium at their centers) are called:
brown dwarfs
one key difference that astronomers use to distinguish between brown dwarfs and high-mass planets is that
brown dwarfs are able to deuterium fusion in their cores, while planets cant
when einstein proposed his general theory of relativity, he suggested some pretty strange ideas about space, time, and gravity. how did scientists in 1919 show that einsteins theory described the behavior of the real world and wasnt just a crazy hypothesis?
by observing starlight coming close to the sun during an eclipse
really massive stars differ from stars with masses like the sun in that they
can fuse elements beyond carbon and oxygen in their hot central regions
according to the general theory of relativity, the presence of mass
causes a curvature (or warping) spacetime
coronal mass ejections from the sun have many serious effect on or near the earth. Which of the following is NOT one of these effects
causing huge clones around the equator of the earth
the hotter region direclty above the suns visible surface is called the
corona
the ten millions of particles that escape the sun each year in the form of the solar wind get out mainly through regions called
coronal holes
Astronomers arrange the stars into groups called spectral classes (or types) according to the kinds of lines they find in their spectra. These spectral classes are arranged in order of:
decreasing surface temperature
for what type of star can astronomers measure the diameter with relative ease?
eclipsing binary stars
in the sun, when a positron and an electron collide they will produce
energy in the form of gamma ray
after the core of a massive star becomes a neutron star, the rest of the stars material
explodes outward as a supernova
astronomers have noticed that the visible filaments in the crab nebula are moving toward us at great speed. how can they know about motions like this?
from the doppler shift in the line radiation from the nebula
astronomers identify main sequence on the H-R diagram with what activity in the course of a stars life?
fusing hydrogen into hellium in their cores
recently, some engineers and scientists have proposed building spaceships with enormous "sails" that catch the solar wind and use it to move the ship. what kinds of principles would be hitting this sail (i.e. what is the solar wind mostly made of)
gamma-rays
interstellar matter refers to
gas and dust that. lies between star
cosmic rays are
high speed atomic nuclei, electrons, and positrons
the granulation pattern that astronomers have observed on the surface of the sun tells us that
hot material must be rising from the suns hotter interior
when an astronomer rambles on and on about the luminosity of a star she is studying, she is table about
how much energy the star gives off each second
studies of the spectra of stars have revealed that the element that makes up the majority of the stars (75% by mass) is
hydrogen
which of the following statements about interstellar matter is FALSE
if the matter were spread out evenly, it would be about as dense as the Earths atmosphere
which of the following is NOT a place where astronomers believe interstellar dust grains can form
in HII regions
if you want to find stars that are just being born, where are the best places to search?
in giant molecular clouds
As astronomers have learned more about the structure of the Sun, they have found that it:
is made entirely of hot gas
if you were to sample a tablespoon of each of the following objects, which of those tablespoons would weigh the most? the one that sampled the
neutron star
the closest star to the sun, Proxima centauri, was recently found to have a plant in its habitable zone. proxima centauri is a main sequence star with a spectral type M. How would its habitable zone differ from the habitable zone of our sun?
it would be significantly closer to proxima centauri than ours is to the sun
Astronomers must often know the distance to a star before they can fully understand its characteristics. Which of the following properties of a star typically requires a knowledge of distance before it can be determined?
its lumoinosity
How long a main sequence star remains on the main sequence in the HR diagram depends most strongly on
its mass
what determines where on the main sequence a star will first plot on the HR diagram?
its mass
An H-R diagram plots the surface temperature of stars against their
luminosity
stars on the main sequence obey a mass-luminosity relation. according to this relation
luminosity is proportional to mass to the fourth power (luminosity increases strongly with mass)
which of the following statements about the main sequence stage in the life of a star is FALSE
main sequence stars are rare in the galaxy, so we are lucky to be living around one
to predict whether a star will ultimately become a black hole, what is the key property of the star we should look at
mass
which of the following characteristics of a single star (one that moves through space alone) is it difficult to measure directly?
mass
stars that lie in different places on the main sequence of the H-R diagram differ from each other mainly by having different
masses
to get the distance to a cepheid variable star, astronomers must take several steps. Which of the following is NOT one of these steps?
measure the star's Doppler shift from its spectrum
wearing a very accurate watch, you volunteer to go on a mission to a black hole in a spaceship that has powerful rockets. you are able to orbit the black hole and stay a little distance OUTSIDE the event horizon. compared to watches on Earth, your watch near the black hole will run
more slowly
cosmic rays differ from other forms of interstellar matter by
moving much faster, at typical speeds of 90% the speed of light
astronomers were surprised to find so many jupiter-mass planets so close to their stars. According to their best theories and models, such "hot Jupiters"
must have formed further out from the star and must have "migrated inward" early on
some years after college (and after you recover from you astronomy class), you get married and exchange gold rings with your sweetheart. What connection is there between the gold in those rings and recent observations of gravitational waves
our new understand is that significant amounts of gold in the universe are produced in the mergers of neutron stars, which can be detected with gravitational waves
you are out on the beach, enjoying the warm sunshine with friends. as you glance up at the sun( only briefly we hope), the part of the sun that you can see directly is called its
photosphere
if most stars are low-mass, and low mass stars typically eject a planetary nebula, why then do astronomers see relatively few planetary nebulae in the sky?
planetary nebulae expand rapidly and soon become too faint to be visible
which of the following is NOT one of the reasons planets around other stars are so difficult to detect?
planets only form very late in the life of a star, just when it is ready to die, and thus last only a very short fraction of the star's life
the material inside the sun is in the form of a
plasma
the material inside the sun is the form of a
plasma
what is part of the process in estimating the age of a cluster of stars?
plot an HR diagram for the stars in the cluster
astronomers call the motion of a star across the sky (perpendicular to our line of sight) is
proper motion
when energy is first produced by fusion deep in the core of the star that energy moves outward mastly by what process
radiation
far away from a black hole (at the distance of another star), which of the following is a possible way to detect it?
search for flickering x rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star
a white dwarf, compared to a main sequence star with the same mass, would always be:
smaller in diameter
the amount of interstellar matter present in our Galaxy is always changing. which of the following processes is NOT a major contributor to that change
some atoms of gas combine in dusty cloud to make more complex molecules
two stars have the exact same luminosity, but star Y is four times dimmer looking than Star X. This means that
star Y is twice as far away as star X
the most likely method for measuring the distance to a star that turned out to be about 30 light years away would be which of the following methods?
stellar parallax
which type of star has the least amount of pressure in its atmosphere?
super giants
which of the following stages will our own sun NOT go through in the future
supernova
I am measuring the spectrum of the stars in a spectroscopic binary system. When one of the stars is moving toward the Earth in its orbit, we observe
that the lines in its spectrum show a blue-shift
when astronauts aboard the international space station (ISS) in space let go of an orange. why is that?
the ISS is falling around the Earth, and in free fall, things feel no weight
a type of star that has turned out to be extremely useful for measuring distances is
the cepheid variables
in 1959, pound and rebka did an experiment to test the prediction of Einstein's theory of general relativity about the relationship between the pace of time and the strength of gravity. when two identical atomic clocks, one on the ground floor and one on the top floor, were compared
the clock on the ground floor became a little bit lighter (weighed less)
which part of the sun has the greatest density?
the core
a friend (who does not have the new awareness which you have gained from this course) suggests that the mechanism that keeps the sun shining as brightly as it does is the burning of coal. you brilliantly challenge his theory! your challenge comes in several related steps; which of the following is one of those steps
the dating of radioactive rocks show that the earth and thus the sun are billions of years old
what observation about disks of dusty material around young stars suggest that planets may be forming in such disks?
the disks show lanes that are empty of dust within them
which of the following is a characteristic of degenerate matter in a white dwarf star?
the electrons get as close to each other as possible and resist further compression
what incident in a massive stars life sets off(begins) the very quick chain of events that leads to a supernova explosion?
the fusion of iron
which of the following is one reason we do not detect pulsar in many remnants of supernova explosions?
the little green men inside put shades on their pulsars for privacy
the higher the luminosity (intrinsic brightness) a Cepheid variable is,
the longer the period of its variations
ninety percent of all stars (if plotted on an H-R diagram) would fall into a region astronomers call
the main sequence
once a black hole forms, the size of its event horizon is determined only by
the mass inside the event horizon
in the first direct detection of gravitational waves by LIGO in 2015, the waves came from
the merger of two black holes
the term "baryon cycle", as astronomers use it, refers to
the movement of interstellar material into the galaxy and into stars and the movement out when stars end their lives
which of the following is NOT a result of supernova explosions?
the neutron star is disrupted and tears apart into many
the strongest force we know is
the nuclear force which holds nuclei together
astronomers have concluded that the suns activity caries in an 11-year cycle. which of the following statements about this cycle is TRUE
the number of sunspots gets larger and smaller over the course of 11 years
which of the following statements about the Sun's photosphere is NOT true
the photosphere is not a solid layer; if a spaceship(that could withstand the heat) fell through it, it wouldnt feel anything when reaching the photospehere
when did scientists begin to understand how the sun produces all the energy that it does?
the process was not well understood until the 1930's
in order for the apparent brightness of a star to be a good indicator of its distance, all stars would have to
the same luminosity
the apparent brightness of stars in general tells us nothing about their distances; we cannot assume that the dimmer stars are farther away. in order for the apparent brightness of a star to be a good indicator of its distance, all the stars would have to be
the same luminosity
the frist time astronomers observed BOTH gravitational waves and electro-magnetic waves from the same event, what they were observing was
the spiraling toward each other of two neutron stars
sunspots are darker than the regions of the sun around them because
they are cooler than the material around them (although still very hot compared to Earth temperatures)
how do astronomers know that pulsating variables stars are actually exploding and contracting in diameter?
they can measure a regularly varying Doppler shift in the spectral lines
your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made)
they were built up from smaller nuclei during a supernova explosion
when the core of a star reaches a temperature of about 100 million degrees(K), something new happens in the core. What is this new event?
three helium nuclei begin fusing carbon (element number 6)
a star whose temperature is decreasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?
to the right
which f these stars will take the SHORTEST time to go from the earliest protostar stage to main sequence>?
you cant fool me, all of these stars take the same time to get to main sequence
which of the follwoing statements about antimatter is TRUE
when a particle of matter and the corresponding particle of antimatter meet, they become pure energy
astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?
when nuclear fusion reactions begin inside its core
a herbig-haro(HH) object is
where a jet from a star in the process of being born collides with (and lights up) a nearby cloud of interstellar matter
which of the following stages can ONLY occur in the life of a low-mass star (whose final mass is less than 1.4 times the mass of the sun)
white dwarf
which of the following stages will the sun definitely go through as it gets older?
you cant fool me, a star like our sun will go through all the phases listed
which of the following can astronomers NOT learn from studying the spectrum of a star?
you cant fool me, all of the characteristics can be learned from studying the spectrum
using a good pair of binoculars, you observe a section of the sky where there are stars of many different apparant brightness. you find one star that appears especially dim. this star looks dimmer bc it is
you cant fool me, it could be any of the reasons listed or a combo of more than one lised
after it experiences a helium flash a star like the sun will have a brief period of stability, fusing helium into carbon (and someitmes oxygen). During this brief stable stage, the star
you cant fool me, none of the answers rpovided is the correct answer
