Galaxies Flashcards
What is the approximate diameter of the Milky Way in parsecs?
About 30,000 Pc.
Describe the appearance of the Milky Way.
- Super massive black hole in centre
- Long line through the sky (plane of the galaxy)
What is the 21cm line and what does it mean?
The 21cm line is to do with radio astronomy - atomic hydrogen produces low energy photons of wavelength 21cm which can pass through the interstellar medium - can be used to determine rotation of the galaxy.
What does a spiral galaxy look like?
Central bulge with spiral arms coming from it.
What does a barred spiral galaxy look like?
Central bulge with almost semi-circular spirals coming from it.
What does an elliptical galaxy look like?
Either spherical or highly elliptical shape.
What does an irregular galaxy look like?
Like a mess - a large cloud.
What is Hubble’s Tuning Fork diagram?
A diagram which classifies galaxies
- Elliptical galaxies from E0 (spherical) to E7 (highly elliptical)
- Splits off into either spirals or barred spirals
- Spiral galaxies from Sa with tightly packed spirals to Sc with spread out spirals
- Barred spirals the same but from SBa to SBc
What type of galaxy is the Milky Way?
Sb type galaxy. (spiral b)
What do some galaxies emit?
Large quantities of radiation in addition to visible light (e.g. radio waves, x-rays)
What is an AGN and what is it powered by?
Active Galactic Nucleus - where the radiation is emitted from. Powered by supermassive black holes at centre of galaxy.
What are the 4 main types of active galaxies?
Radio galaxies, Seyfert galaxies, Quasars and Blazers
How were Quasars discovered?
By radio astronomers who observed a strong radio source but was not until an occultation of the moon that it was matched to an optical component.
What are Quasars?
Distant galaxies with high redshifts.
What is the Local Group? Give 3 examples of galaxies in the Local Group.
The galaxies which are close to us.
e.g. Milky Way, Andromeda, Triangulum
