Chapter 25: The Milky Way Flashcards
How big is the Milky Way?
It is 30 kpc (100,000 ly across)
How many stars does the Milky Way contain?
100 billion stars
Where is the sun?
On the edge to the left
The longer a Cepheid’s period …
the greater its luminosity
What can help you find out how far away the star is with observed brightness?
Knowing the star’s periodicity
What are the variables for a Cephid?
Throughout galaxy, pulsation period of 1 - 50 days, avg luminosity related to pulsation
What are the RR Lyrae variables?
in globular clusters, pulsation periods less than a day, same luminosity
What are the components of the milky way?
disk, halo, and central buldge
What is a galaxy’s disk?
Contains gas and dust along with metal-rich stars
What is a galaxy’s halo?
Composed almost exclusively of old, metal-poor stars.
What is the galaxy’s central bulge?
A mixture of both types of stars.
Open clusters
Young, disk, metal-rich
Globular clusters
Old, halo, metal-poor
What does orbital speed of an object depend on?
the amount of mass between it and the galactic center.
As we go out the velocity should diminish but it doesn’t, why?
evidence of dark matter (we can’t see it)
