Problem Set 9B
In the time-lapse movie by Andrea Ghez and collaborators, one of the stars comes within 90 AU of a massive object in the center of the galaxy. From the orbit of that star and of the other neaby stars, the mass within that 90 AU orbit is computed to be about
4 million times time mass of the sun
21-cm radio radiation is emitted by
cold hydrogen gas
In which part of the Milky Way galaxy is the Sun?
disk
The galactic halo contains about as much gas and dust as the galactic disk.
false
What kind of radiation is used to find the location and shape of the Milky Way's spiral arms?
radio waves
In what part of the galaxy are O and B stars most often found?
spiral arms
The Milky Way is
spiral galaxy
The effect of gravitational waves has been seen in
the loss of energy in a binary system of two neutron stars
Herschel's attempt to map the Milky Way by counting stars led to an inaccurate estimate of the Galaxy's size because he was unaware of absorption by interstellar dust.
true
What shows that the mass of the Milky Way extends beyond the visible disk?
Mass deduced from orbits of globular clusters and stars outside the visible disk.
Most of the mass of the Milky Way galaxy is known to be
What constitutes most of the Milky Way's mass is not known.
The large mass in the center of the Milky Way within a radius twice that of Pluto's orbit is the strongest evidence for
a supermassive black hole at the galactic center
21-cm light is associated with
an electron flipping its spin in a hydrogen atom
About how far is the Sun from the center of the Milky Way?
30,000ly
Match the following objects to the part of the galaxy in which they are ordinarily found 1. global clusters 2. open clusters 3. supermassive black hole 4. gas and dust
1-halo 2- disk and bulge 3-bulge, but not the disk 4- disk and bulge
The following features of space and time appeared obvious to people who could travel and measure distances small compared to the size of the Earth. They have had to be discarded as we learned more about the universe. Order them from 1 to 3 according to the order in which they were discarded (1 = first to be discarded, 3 = last to be discarded).
1. earth is flat 2. earth at rest 3. space is flat
What is the diameter of the disk of the Milky Way?
100,000 ly
How long does the Sun take to orbit the galaxy?
225 million years
According to Figure 14.6 of the 6th edition (also Fig. 14.6, fourth and fifth editions), a Cepheid variable with luminosity 1000 times that of the Sun has a period of roughly
3 days
Gravitational waves are a consequence of
Einstein's law of gravity, but not of Newton's