15) Our Place In The Galaxy ✅

Question 1

What is our Galaxy called?

Answer 1

Milky Way

Question 2

What is Milky Way in Latin?

Answer 2

Via Lactea

Question 3

How far is the Sun from the centre of our Galaxy?

Answer 3

~10 kpc

Question 4

What is the radius of our Galaxy?

Answer 4

~15 kpc

Question 5

What type of galaxy is the Milky Way?

Answer 5

Barred Spiral Galaxy

Question 6

Where are open clusters of young stars found?

Answer 6

In the Spiral Arms

Question 7

Why can’t we see the centre of the Galaxy using visible light?

Answer 7

The Centre of the Galaxy is blocked by dust and dense gas

Question 8

What is the Doppler Principle?

Answer 8

The Doppler Principle is that relative motion changes the frequency or wavelength of observed waves. We notice this change mainly with sound waves

Question 9

What does it mean if the observed wavelength is longer than it should be?

Answer 9

The object is moving away from us

Question 10

What does it mean if the observed wavelength is shorter than it should be?

Answer 10

The source is moving towards us

Question 11

What can the Doppler Shifts tell us about the Milky Way?

Answer 11

The received wavelengths are supposed to be 21 cm, but they aren’t exactly. This will tell us the relative velocities of the different parts of the Milky Way and how it’s rotating

Question 12

What is redshift?

Answer 12

Redshift is receding sources of waves

Question 13

What is blueshift?

Answer 13

Blueshift refers to sources that are approaching us

Question 14

What is the Hubble Classification System?

Answer 14

Edwin Hubble invented a classification of galaxies and grouped them into four classes: spirals, barred spirals, ellipticals and irregulars

Question 15

What is the used system for the classification of Galaxies?

Answer 15

Hubble Classification System

Question 16

How did Hubble distinguish different spiral galaxies?

Answer 16

• Adding letters a,b and c
  (according to the size of the
  nucleus and ‘openness’ of spiral
  arms)
• Added a number to the elliptical class according to galaxy shape

Question 17

What type of galaxy is this?

Answer 17

Barred spiral

Question 18

What type of galaxy is this?

Answer 18

Spiral

Question 19

What type of galaxy is this?

Answer 19

Elliptical

Question 20

What type of galaxy is this?

Answer 20

Irregular

Question 21

What is the diagram that classifies galaxies?

Answer 21

Tuning Fork Diagram

Question 22

What does the Tuning Fork Diagram look like?

Answer 22

Barred spirals are on the bottom

Spirals are on the top

Question 23

How many theories are there regarding the formation of galaxies?

Answer 23

2

Question 24

What is the theory on the formation of galaxies from gas?

Answer 24

Vast clouds of gas and dust collapsed gravitationally, allowing stars to form

Question 25

What is the theory on the formation of galaxies from lumps of matter?

Answer 25

Lumps of matter were already present in the Universe. They clumped together under their mutual gravitational attraction to form galaxies

Question 26

What type of galaxy is believed to be the earliest type?

Answer 26

Elliptical

Question 27

What are 'active galaxies'?

Answer 27

Active galaxies are galaxies that have a small core of emission in a normal galaxy. It emits huge amounts of radiation in wavebands such as X-ray and radio regions

Question 28

What are 3 types of active galaxies?

Answer 28

- Seyfert galaxies - Quasars - Blazars

Question 29

What is an Active Galactic Nucleus (AGN)?

Answer 29

An Active Galactic Nucleus is a compact region at the centre of a galaxy that have a much higher luminosity over a portion of the electromagnetic spectrum which indicates that the luminosity isn't produced by stars

Question 30

What is an AGN powered by?

Answer 30

Matter falling onto a supermassive black hole The heat caused by speed/ the effect of it falling into the black hole ---> enormous radiation across the electromagnetic spectrum. | (--->) means produce

Question 31

What does an AGN influence?

Answer 31

Other stars using its gravitational influence

Question 32

What does an AGN emit?

Answer 32

Galactic jets of positrons and electrons in 2 narrow beams at speeds (close to the speed of light)

Question 33

What are Seyfert galaxies?

Answer 33

Seyfert Galaxies are galaxies that have a bright nucleus and emit strongly in the IR, UV and X-ray regions

Question 34

Who discovered Seyfert galaxies?

Answer 34

Seyfert galaxies were discovered by Carl Seyfert in 1943

Question 35

What are Quasars?

Answer 35

A quasar is an extremely luminous AGN that emits strongly in the UV and X-ray regions.

Question 36

What do Quasars appear like?

Answer 36

Quasars appear star-like on images and have large redshifts

Question 37

What are BL Lacertae Objects (Blazars)?

Answer 37

Blazars are compact quasars where the galactic jets are pointing towards us

Question 38

What is the approximate size of the Local Group?

Answer 38

3 Mpc

Question 39

Name five galaxies our local group.

Answer 39

``` Any five of: Andromeda Galaxy Large Magellanic Cloud Small Magellanic Cloud Triangulum Galaxy Milky Way Pegasus Dwarf etc. ```

Question 40

Describe our 'Local group'

Answer 40

Contains about 50 galaxies and are held together by mutual gravitation

Question 41

Which cluster is the Milky way in?

Answer 41

Virgo Cluster

Question 42

Which supercluster is the virgo cluster in?

Answer 42

Laniakea Supercluster

Question 43

How does the side of our galaxy look like + what does it contain?

Answer 43

- Halo of globular clusters - Disc of spiral arms of young stars/gas ----> dust and sites of star formation

Question 44

What is evidence for a massive black hole at the centre of our galaxy?

Answer 44

A nuclear bulge

Question 45

What do the spiral arms contain in the milky way galaxy?

Answer 45

Gas and dust that are sites of future star formation

Question 46

Why do the Spiral arms of the galaxy emit high levels of radio waves?

Answer 46

The spiral arms contain hydrogen atoms that reveal themselves by emitting radio waves.

Question 47

What causes the 21cm radio waves of the spiral arms to be produced?

Answer 47

They are produced when single electrons orbiting hydrogen nuclei reverse their spin. (Small loss in energy is radiated as electromagnetic radiation, which has a wavelength of 21cm)

Question 48

How has the received 21cm radio waves told us about the structure and rotation of the galaxy?

Answer 48

The 21cm (centimetre) range is known as the Hydrogen line which allows us to see past clouds of interstellar cosmic gas and dust. The centre of the galaxy has a lot of this. It has told us about the structure and rotation of the galaxy.

Question 49

What do galaxies emit?

Answer 49

radiation that can be seen in the electromagnetic spectrum. This includes visible light, radio waves, ultraviolet, infrared, x-rays and gamma rays.

Question 50

The amount of material spinning around the black hole forms an...

Answer 50

Accretion disk

Question 51

How can scientists find black holes?

Answer 51

Scientists cannot see the black hole but they can sometimes see radiation at different wavelengths forming an accretion disc, or by looking for jets of material thrown out of the galaxy by the gravity of the black hole.

Question 52

What's the oldest solar system object that we know of?

Answer 52

Quasars

Question 53

What shape are Seyfert galaxies usually?

Answer 53

Spiral or irregular

Question 54

When did the first galaxies begin to take shape?

Answer 54

Approx 13 billion years ago