Ch. 17 The Milky Way Galaxy
An average star that is farther out from the galactic center than our sun would most likely be moving
at about the same speed as our sun
The closest star to our sun is about four light years away, in the center of our galaxy, a typical distance between neighboring stars would be
.04 light years
The closest star to our sun is about four light years away. In the center of our galaxy, a typical distance between neighboring stars would be
.04 light years
The distance from our sun to the center of the Milky Way Galaxy is roughly
30,000 light years
The constellation Sagittarius is where the Milky Way
Is thickest
The source that is called Sgr A* emits
both x-rays and radio waves
In our Milky Way, the Orion Spur is
closest arm to our sun
The velocities with which stars and gas clouds orbit the center of our galaxy is measured by observing their
doppler shifts
The Big Bang theory predicts that most of the dark matter in our galaxy and elsewhere must consist of something other than the known chemical elements. This prediction
has been tested by looking for rogue planets
Cepheid variable stars with the same luminosity usually
have similar periods
The stars of the Milky Way are mostly found
in a band of stars stretching across the sky
One indication that there is a lot of invisible matter in the outer halo of our galaxy is that the stars in that region orbit with velocities that
increase with increasing distance from the center
Extragalactic nebulae such as the Great Nebula in Andromeda were not immediately recognized as galaxies similar to our own Milky Way because they were thought to be
smaller, nearby objects
The mass of Sgr A* has been determined by observing
the motions of stars near it
The main evidence for the presence of invisible matter in our galaxy is
the velocities with which stars orbit
Our sun is roughly at the center of
the visible part of the Milky Way.
The theory that dark matter is not real and is just a a problem with our theory of gravity has been falsified by
an observation of what happens when clusters of galaxies collide
How many stars similar to our sun would need to be collected at once place to equal the power output of Sgr A*?
a million
The overall shape of our Milky Way Galaxy is thought to be
a spiral somewhat like the nearby Andromeda Galaxy
Observations of the collision of two galaxy clusters have shown that dark matter
is not the result of an incorrect theory of gravity
The motions of the stars near Sgr A* make it possible to determine its
mass
The mass that is distributed in different parts of our Milky Way Galaxy is estimated by
measuring how stars orbit the center of the galaxy
Near the center of the Milky Way there is an intense radio source whose mass is approximately three
million solar masses within several light days of the center.
In comparison to RR Lyra variables, Cepheid variable stars are
more luminous and less common
In a spiral galaxy, long-lived stars such as our Sun
move in and out of spiral arms
The observation that stars father from the center of our galaxy orbit faster is thought to mean that
much of the mass is outside the central bulge
Population I stars in our galaxy include
only younger stars such as our sun.
The population II stars of our Milky Way
orbit the central bulge in all directions.
The doppler shift of familiar spectral lines from gas clouds and stars in our galaxy measures their
orbital velocities within the galaxy.
