Astronomy Exam 3
The type of galaxy that consists almost entirely of old stars and is thus less blue (more yellow and reddish) than the other types is?
Elliptical Galaxy
What forces caused the gas in the thin disk to fragment into clouds or clumps with masses like those of star clusters?
Gravitational
What equilibrium says that there is a balance between two forces at every point within a star. One force is the inward force of gravity. The other force is the pressure in the gas caused by its temperature?
Hydrostatic Equilibrium
A stellar black hole ( or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star true or false
True
Energy is generated in the core by the fusion of hydrogen to form helium true or false
True
In general theory of relativity, the Einstein field equations relate the geometry of space-time with the distribution of matter within it. True or False
True
Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object True or false
True
at the end of the p-p chain of nuclear fusion in the Sun, hydrogen nuclei have been converted into:
a helium nucleus
Which type of galaxy is observed to contain mostly older stars?
elliptical
In the Sun, when a positron and electron collide, they will produce:
energy in the form of a gamma ray
If you are in a freely falling elevator near the top of a tall building as the elevator falls, your weight would be?
equal to zero-you would be weightless
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is from us, the
faster it is moving away from us
what method would astronomers use to find the distance to a remote quasar?
finding the redshift and using Hubble's Law
Most spiral galaxies consist of:
flat, rotating disk containing stars, gas, dust, and bulge.
Where would you look for the youngest stars in the Milky Way?
in the disk
Which of the following is NOT a characteristic of a spiral galaxy?
it has quite a bit of gas and dust in it
What happens to the positron created during the p-p chain of nuclear reactions inside the sun?
it quickly collides with an electron and turns into gamma-ray energy
What was especially noteworthy about the Sagittarius Dwarf galaxy when it was discovered among the small galaxies near the milky way?
it was on a collision course with the Milky way and would be swallowed by it eventually
When a large nucleus breaks apart( or is broken apart) into two smaller pieces, this is called?
nuclear fission
Where in the Sun does fusion of hydrogen occur?
only in the core
how are galaxies and quasars related?
quasars are active supermassive black holes at the centers of galaxies
Why do astronomers think that there are fewer quasars today than there were billions of years ago?
quasars are seen when the supermassive black hole at the center of a galaxy has a lot of " food to eat" (stars and gas) and the amount of available food tends to decrease with time
Compared to the mass of our own Milky Way galaxy, the total mass we estimate for the the Andromeda Galaxy is?
somewhat bigger
Our Milky way is what type of Galaxy
spiral
When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?
the ISS is falling around the Earth, and in free fall, things feel no weight
Which of the following statements about the nuclear bulge of our galaxy is FALSE?
the best way to learn more about it is to observe higher energy radiation, such as ultraviolet and x-rays
What observation in astronomy made AFTER the discovery of quasars, was a big help to astronomers in figuring out what quasars really were?
the discovery that the Milky way galaxy has a black hole at the center with enough mass for 4 million suns
If a nearby galaxy still acts like a quasar today, what is the most likely explanation?
the galaxy must be undergoing a collision with another galaxy that is providing fresh fuel for its central black hole
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
For galaxies that have super massive black holes at their centers, how do astronomers find that the mass of the host galaxy and the mass of the black hole are realated?
the more massive the galaxy, the more massive the central black hole
how do quasars demonstrate that the universe evolves with time?
the number of quasars reached a maximum some time ago, and now the numbers have been declining
Herschel was right about:
the shape of our system, but wrong about where the Sun lies within the disk
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
their shape
The Andromeda galaxy ( our nearest spiral neighbor) has spectral lines that show a blue shift. from this we may conclude that
this particular nearby galaxy is moving toward us
A globular cluster is a spherical collection of stars that orbits a galactic core true or false
true
Astronomers use the redshift and using Hubble's Law to find the distance to a remote quasar true or false
true
Collapsar is the shortened form to describe a collapsed star. When an old star no longer has enough fuel for significant fusion reactions. true or false
true
Gravitational forces caused the gas in the thin disk to fragment into clouds or clumps with masses like those of star clusters true or false
true
the bubbles in the galaxy may be evidence that the super massive black hole at the center of our galaxy was a quasar a few million years ago. true or false
true
which of the following objects is considered useful to astronomers as a "standard bulb" for determining distances?
type Ia supernovas
after several decades of observation, astronomers have concluded that quasars are?
very powerful and compact sources of energy at the centers of distant galaxies
What have we learned from the work of Harlow Shapley and others about the location of the Sun in the Milky Way Galaxy?
we are in the disk of the Galaxy, about 3/5 of the way from the center
Which of the following can a black hole not "eat" (swallow) ?
you can't fool me, black holes can eat anything
Which galaxy is the closet big galaxy to our Milky Way?
Andromeda Galaxy
Which of the following objects do many astronomers believe is a black hole?
Cygnus X-1
Elliptical galaxy: a galaxy with an elliptical shape, little interstellar matter, and spiral arms. true or false
False
Nuclear fusion: a nuclear reaction in which atomic nuclei of high atomic number fuse to form a heavier nucleus with the release of energy True or Flase
False
What is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other?
Friction
The very strong source of radio waves at the center of our Galaxy is called?
Sagittarius A
Physicists Kelvin and Helmholtz in the last century proposed that the source of the Sun's energy could be:
Slow contraction
A large explosion that takes place at the end of a star's life cycle is called?
Supernova
Dwarf elliptical galaxies are elliptical galaxies that are smaller than ordinary elliptical galaxies true or false
TRUE
to predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?
diameter
Which type of galaxy is very difficult to see, but (astronomers recently realized) may be very common?
dwarf ellipitcal
