Galaxies

Question 1

In which constellation seen from Earth is the centre of the Milky Way located?

Answer 1

Sagittarius

Question 2

What is a Galaxy?

Answer 2

A group of billions of stars bound together by gravity

Question 3

What is in the centre of a galaxy called?

Answer 3

A bulge of stars, also called a galactic nucleus

Question 4

Outside of the galactic nucleus where are the rest of the stars located?

Answer 4

On a narrow disc or disk

Question 5

On the disc what is the dust in between stars called?

Answer 5

Interstellar medium

Question 6

From above the disc is made up of different what of stars?

Answer 6

Spiral arms

Question 7

What is the area called in the centre of a galaxy where lots stars are formed?

Answer 7

The galactic bar

Question 8

Where is the best place to view the centre of the galaxy from Earth?

Answer 8

The Southern Hemisphere

Question 9

How is our solar system Angled to the disc of the Galaxy?

Answer 9

It is slightly above the main disc and is really quite tilted

Question 10

Which is w particularly useful wave length to use when observing the Milky Way? Why?

Answer 10

21cm wavelength, in the radio wave category. This is useful because hydrogen gives this wavelength off and most matter in the universe is hydrogen , these wavelengths tend to go straight through material that would absorb visible waves

Question 11

How are hydrogen waves picked up?

Answer 11

By huge radio telescopes or arrays of many of them

Question 12

Around how far away from the centre bulge / galactic nucleus is the Earth?

Answer 12

Around 2 thirds of the way out

Question 13

What are groups of stars called?

Answer 13

Clusters

Question 14

What are the 2 types of clusters?

Answer 14

Open clusters and globular clusters.

Question 15

What are open clusters?

Answer 15

A group of stars which are loosely bound by each other’s gravity. All the stars are around the same age as they formed from the same nebula, they don’t live long from around a few 100 million to 1 billion years. They are located on the disc

Question 16

What are globular clusters?

Answer 16

A roughly spherical group of old stars and have a stronger mutual gravitational attraction. They are larger than open clusters and orbit the centre of the galaxy above or below the disc in what is call d the galactic halo

Question 17

The Milky Way has approximately how many globular clusters? Counted so far

Answer 17

158

Question 18

What are all the ams of a galaxy doing?

Answer 18

Rotating around the middle of the galaxy

Question 19

How long does it take a galaxy to rotate approximately?

Answer 19

225 - 250 Million years

Question 20

What happens to the wavelength (21cm hydrogen)of an object is moving away from where you are observing it? What is this called?

Answer 20

We’ll measure longer than 21cm which will make it appear nearer red on the wavelength spectrum. This is redshift.

Question 21

What happens to the wavelength (21cm hydrogen) of an object if it is moving towards where you are observing it? What is this called?

Answer 21

We’ll measure shorter than 21cm, making it nearer blue on the wavelength spectrum. This is called blueshift.

Question 22

How do we know the galaxy is rotating?

Answer 22

By measuring blueshift and redshift

Question 23

What are the 3 types of AGN?

Answer 23

Seyfert, Quasars and Blazars

Question 24

What does AGN stand for? What is it?

Answer 24

Active Galactic Nuclei

They are galaxies which have a radiation emitting centre

Question 25

What is a Seyfert galaxy?

Answer 25

An AGN that look like normal galaxies in visible wavelengths but have a brighter core, which is radiation emitting. It is aligned so it’s North and South galactic poles are not in the direction of us/ Earth, they have the same sort of plane/ poles as out galaxy

Question 26

How many different types of Seyfert galaxies are there? How are they different?

Answer 26

Type I emits a lot of UV and X-ray radiation Type II emits a lot of infrared radiation There are 2 types in total

Question 27

What is a quasar galaxy?

Answer 27

An AGN that doesn’t appear to have much of a galaxy around it but is bright across the whole of the EM spectrum, they are strong radio sources as they have been red shifted, meaning they are very far away and young

Question 28

What are Blazars?

Answer 28

An AGN similar to a Seyfert but is aligned differently such that the galaxies galactic North or South is directed at us/ Earth. They vary massively in brightness over time and fire huge amounts of gamma rays towards us

Question 29

What does radiation come out of galaxies in?

Answer 29

In jets of energy

Question 30

What are the types of galaxies (there shape/ classification)?

Answer 30

Elliptical galaxies (nearly circular to very eccentric) Lenticular , a central bulge surrounded by a disc but the disc isn’t broken down into spirals Spiral galaxies barred and regular Irregular (2 galaxies have crossed and messed them up)