Topic 4 Flashcards
Describe the look of the Milky way from outside the galaxy
It has a nuclear bulge in which there is a supermassive black hole in the center of the galaxy
What kind of galaxy is the Milky Way?
A spiral galaxy
What is the diameter of the Milky Way?
30kpc (100,000 ly)
Where does the Sun lie in the Milky Way galaxy?
On a spiral arm approximately half way between the nuclear bulge and the rim
How many major arms are there in the Milky Way and where do they spiral out from?
They are 4 major arms spiraling out from the nuclear bulge
What kind of stars do the major arms of the Milky way contain?
They contain young stars, opaque dust and they are sites of star formation
Where are globular clusters located?
1-2 kpc above and below the galactic disk
How do astronomers use 21cm radio waves rather than visible light to determine the rotation of our galaxy?
Hydrogen emits very definite wavelengths - one of these wavelengths is 21cm radio waves.
Because hydrogen is so abundant we can receive reflected radio wave signals from different parts of the galaxy.
Radio waves can pass through dust clouds so they are useful.
We can look at how much the radio waves have red shifted or blue shifted to determine the speed of the the hydrogen relative to us.
Using this we can map the spiral arms of our galaxy
Describe the shape of a spiral galaxy
Like the milky way - a disk shape with a nuclear bulge
Describe the shape of a barred spiral galaxy
The same as a spiral galaxy but with a bright central barred structure
Describe the shape of an elliptical galaxy
A smooth spheroid structure with a gradual decrease in brightness from the center of the galaxy to the rim
Describe the shape of an irregular galaxy
A galaxy with no particular structure or symmetrical properties
What type galaxy (Hubble’s tuning fork) is the Milky way?
An Sb type galaxy
What is an AGN?
An active galactic nucleus -where some galaxies’ nuclei emit above average amounts of radiation (they have a higher luminosity)
What is found at the center of an AGN?
A supermassive blackhole
