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GCSE EDEXCEL Astronomy (paper 2 ONLY) > 15) Our Place In The Galaxy ✅ > Flashcards

15) Our Place In The Galaxy ✅ Flashcards

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1
Q

What is our Galaxy called?

A

Milky Way

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2
Q

What is Milky Way in Latin?

A

Via Lactea

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3
Q

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

A

~10 kpc

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4
Q

What is the radius of our Galaxy?

A

~15 kpc

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5
Q

What type of galaxy is the Milky Way?

A

Barred Spiral Galaxy

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6
Q

Where are open clusters of young stars found?

A

In the Spiral Arms

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7
Q

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

A

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

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8
Q

What is the Doppler Principle?

A

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

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9
Q

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

A

The object is moving away from us

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10
Q

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

A

The source is moving towards us

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11
Q

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

A

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

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12
Q

What is redshift?

A

Redshift is receding sources of waves

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13
Q

What is blueshift?

A

Blueshift refers to sources that are approaching us

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14
Q

What is the Hubble Classification System?

A

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

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15
Q

What is the used system for the classification of Galaxies?

A

Hubble Classification System

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16
Q

How did Hubble distinguish different spiral galaxies?

A
  • 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
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17
Q

What type of galaxy is this?

A

Barred spiral

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18
Q

What type of galaxy is this?

A

Spiral

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19
Q

What type of galaxy is this?

A

Elliptical

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20
Q

What type of galaxy is this?

A

Irregular

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21
Q

What is the diagram that classifies galaxies?

A

Tuning Fork Diagram

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22
Q

What does the Tuning Fork Diagram look like?

A

Barred spirals are on the bottom

Spirals are on the top

23
Q

How many theories are there regarding the formation of galaxies?

A

2

24
Q

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

A

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

25
Q

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

A

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

26
Q

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

A

Elliptical

27
Q

What are ‘active galaxies’?

A

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

28
Q

What are 3 types of active galaxies?

A
  • Seyfert galaxies
  • Quasars
  • Blazars
29
Q

What is an Active Galactic Nucleus (AGN)?

A

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

30
Q

What is an AGN powered by?

A

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

31
Q

What does an AGN influence?

A

Other stars using its gravitational influence

32
Q

What does an AGN emit?

A

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

33
Q

What are Seyfert galaxies?

A

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

34
Q

Who discovered Seyfert galaxies?

A

Seyfert galaxies were discovered by Carl Seyfert in 1943

35
Q

What are Quasars?

A

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

36
Q

What do Quasars appear like?

A

Quasars appear star-like on images and have large redshifts

37
Q

What are BL Lacertae Objects (Blazars)?

A

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

38
Q

What is the approximate size of the Local Group?

A

3 Mpc

39
Q

Name five galaxies our local group.

A 
Any five of:
Andromeda Galaxy
Large Magellanic Cloud
Small Magellanic Cloud
Triangulum Galaxy
Milky Way
Pegasus Dwarf
etc.
40
Q

Describe our ‘Local group’

A

Contains about 50 galaxies and are held together by mutual gravitation

41
Q

Which cluster is the Milky way in?

A

Virgo Cluster

42
Q

Which supercluster is the virgo cluster in?

A

Laniakea Supercluster

43
Q

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

A
  • Halo of globular clusters
  • Disc of spiral arms of young stars/gas
    —-> dust and sites of star formation
44
Q

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

A

A nuclear bulge

45
Q

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

A

Gas and dust that are sites of future star formation

46
Q

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

A

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

47
Q

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

A

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)

48
Q

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

A

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.

49
Q

What do galaxies emit?

A

radiation that can be seen in the electromagnetic spectrum.

This includes visible light, radio waves, ultraviolet, infrared, x-rays and gamma rays.

50
Q

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

A

Accretion disk

51
Q

How can scientists find black holes?

A

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.

52
Q

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

A

Quasars

53
Q

What shape are Seyfert galaxies usually?

A

Spiral or irregular

54
Q

When did the first galaxies begin to take shape?

A

Approx 13 billion years ago

GCSE EDEXCEL Astronomy (paper 2 ONLY) (9 decks)

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