The metallic hydrogen in Jupiter's interior contributes to
its strong magnetic field
The thermal emission from several giant planets
is larger than would be predicted from the amount of sunlight absorbed by the planets
The high level of motions and activity in Jupiter's atmosphere results from
Convection driven in part by the interior heat of the planet
The poles and equator on Jupiter do not rotate at the same rate, implying that
Jupiter's visible surface is made of liquid or gas
Uranus is very similar to
Neptune
Moons that come too close to a planet
will disintegrate
Prior to the Cassini mission, we had not made a good map of the surface features on Titan because
it has a relatively opaque atmosphere
The densest of Jupiter's large moons are found
close to Jupiter
This moon of Jupiter has a relatively smooth icy surface suggesting an underlying ocean.
Europa
A key ingredient in discovering Pluto was
comparison of photographs taken at different times
The New Horizons spacecraft revealed that Pluto
has surprisingly complex surface
We have determined the surface compositions of asteroids by
finding pieces of them on the ground , studying spectra of sunlight reflected from them
Comets originate
from cloud surrounding the Solar System
Pluto is likely one of the largest members of
the Kuiper belt
A meteor shower results when
the earth passes through the remnants of a comet
Comets are comprised mainly of
ice
If all the asteroids in the asteroid belt were assembled into a planet, it would be
less than 1/1,000 of Earth's mass
No full-sized planet formed between Mars and Jupiter because
Jupiter's gravity kept stirring things up so no large object was safe from big collisions
A star may be a variable star because
it alternately expands and contracts
The Shapley-Curtis debate
was important philosophically because the topics touched on our place in the Universe
That "spiral nebulae" were other galaxies like the Milky Way was first established when
the new 100-inch telescope was used to resolve some of them into stars
Galaxy distances are determined
by a large variety of techniques that have to be used together, depending on the circumstances
Distance measurements to the galaxies around us show that
the Milky Way is part of a galaxy group in which it and M31 are surrounded by many small galaxies
The biggest change in our view of our place in the Universe compared with the view 100 years ago is
then, we thought that the "Universe" was just the Milky Way
What is the evidence there is dark matter beyond the disks of spiral galaxies?
the stellar mass distribution does not account for the rotation curve of the galaxies
We think that either dark matter is in the form of low mass brown dwarfs and wandering planets, or
the Universe is filled with an undetected type of nuclear particle
Galaxies are distributed
in vast sheets and filaments that make a structure a little like soap bubbles, in clusters and groups
Gravitational lenses in galaxy clusters are used
to confirm that the clusters have huge amounts of dark matter
Spiral arms are prominent in some galaxies because
they show where young and bright stars have formed
The various types of galaxy
include spirals, ellipticals, and irregulars
We see where the young stars are in a galaxy most easily when we look in
the ultraviolet and far infrared
In very deep images that let us detect very distant and hence young galaxies, we find them to be
generally to be smaller and with less regular structure compared with nearby ones
We know about the black hole in the Galactic Center because
from Newton's and Kepler's laws
The nature of quasars was initially confusing because
their emission lines were at peculiar wavelengths
An active nucleus can be identified by
all of the above
Active galaxy nuclei are powered by
matter falling into a very massive black hole
The rapid variability in the outputs of quasars and other active nuclei shows that
the nuclear sources are very small
In comparison with the black holes in some other galaxies, the one in the Galactic Center is curious because
it seems to be making very little energy
The Galactic Center was hidden from astronomers for many years because
it is hidden in the visible by clouds of interstellar dust
Galaxies undergoing starbursts
are forming massive stars rapidly and in exceptionally large numbers
Our own galaxy
is pulling apart some nearby galaxies and will eventually consume them
Ring-shaped galaxies and galaxies with tails of stars are evidence for
galaxy collisions
Star formation
tends to be enhanced where peaks in the local density compress the molecular clouds
Galaxy collisions can
trigger high rates of star formation
Saturn's rings are much more visible than other rings because
they are small particles largely of ice
Look at the graph at the left. What is the period for this star
4.5 days
You have measured the period of a Cepheid variable and found that it is 5 days. From the graph at left, what is the luminosity of this star?
10^3 LSun
Astronomers have found that there is a relationship between the mass of stars in a galaxy and the mass of the black hole in the galaxy's center.
this is surprising because the black hole would seem to be too small to influence all the stars
In the collection of pictures above, which galaxy is an elliptical galaxy?
b.
The Milky Way most closely resembles which of these galaxies
a.