Quiz 13
If a galaxy's overall mass-to light ratio is 100 solar masses per luminosity, and its stars account for only 5 solar masses per solar luminosity, how much of the galaxy's mass must be dark matter?
95 percent
What does the universe look like on very large scales
Galaxies appear to be distributed in chains and sheets that surround great voids
Why do we call dark matter "dark"
It emits no or very little radiation of any wavelength
If there is no dark matter in the Milky Way Galaxy, what is the best alternative explanation for the observations
Our understanding of gravity is not correct for galaxy-size scales
Why do we believe 90 percent of the mass of the Milky Way is in the form of dark matter
The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo
What is the evidence of an accelerating universe
White-dwarf supernovae are slightly dimmer than expected for a coasting universe
What is the ultimate fate of an open universe
all matter decays to a low-density sea of photons and subatomic particles
NO QUESTION?
approximately spherical and about 10 times the size of the galaxy halo
Compared to the central regions of spiral galaxies, we expect elliptical galaxies to have
higher mass- to light ratios because stars in elliptical galaxies are dimmer that those in spirals
What do we mean when we say that a particle is a weakly interacting particle
it interacts only though the weak force and the force of gravity
Gravitational lensing occurs when
massive objects bend light beams that are passing nearby
Which of the following particles are baryons
protons
What is meant by "dark energy"
the agent causing the universal expansion to accelerate
Measuring the amount of deuterium in the universe allows us to set a limit on
the density of ordinary (baryonic) matter in the universe
When we see the spectral line of a galaxy is broadened, this is, spanning a range of wavelengths, we conclude that
there are different Doppler shifts among the individuals stars in the galaxy
How are rotation curves of spiral galaxies determined beyond radii where starlight can be detected
through observations of the 21 cm line of atomic hydrogen
What might be causing the universe to accelerate
we don't know!- but we call it "dark energy"
Which of the following is an example of baryonic matter
you
