Topic 15 - Our place in the galaxy Flashcards
How does the Milky Way appear when viewed through binoculars?
Dust, stars and nebulae are visible.
What is the radius of our galaxy?
50 000 ly
How far is the Sun from the centre of our galaxy?
25 000 ly
What does the disc of the Milky Way contain?
Young stars, gas, dust and sites of star formation.
Where are the globular clusters located and what do they contain?
They are above and below the main plain of our galaxy ( or in the “halo”) and contain old stars.
Why do we use 21cm radio waves, rather than visible light, to determine the structure and rotation of our galaxy?
- Dust blocks visible light
- Spiral arms contain hydrogen atoms which emit radio waves that correspond with a wavelength of 21cm
How do the radio waves determine the structure and rotation of our galaxy?
The radio waves are Doppler-shifted which indicates relative movement, and helps us determine the shape of our galaxy.
What is the Local Group?
A group of galaxies near the Milky Way that are gravitationally bound together.
What are the principal components of the Local Group?
- The Milky Way
- The Andromeda Galaxy
- The Large and Small Magellanic Clouds
- The Triangulum Galaxy
What is the Hubble Classification System?
Groups galaxies by shape.
What are the four shapes in the Hubble Classification System?
- Spiral
- Barred spiral
- Elliptical
- Irregular
What type of galaxy is the Milky Way?
Barred Spiral (SBb)
In the Tuning Fork Diagram, what do the letters a,b,c mean?
They correspond with the size of the nucleus and the openness of the galaxy; “a” has a larger nucleus and more tightly wrapped arms
What do some galaxies emit?
Large quantities of radiation (radio waves and x-rays) in addition to visible light.
What do active galaxies have at their centre?
An Active Galactic Nucleus (AGN) which is powered by a central super-massive black hole.
