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Astronomy GCSE > Galaxies > Flashcards

Galaxies Flashcards

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1
Q

What is a galaxy?

A

A gravitationally bound collection of stars with little else between them.

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2
Q

What does an Sa galaxy look like?

A

Prominent nucleus, tightly wound arms.

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3
Q

What does an E0 galaxy look like?

A

Almost circular (with a gradual decrease in brightness from the centre outwards).

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4
Q

What do spiral galaxies look like?

A

Flattened and disc-shaped, with arms protruding from its nucleus.

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5
Q

Give three examples of a spiral galaxy.

A

Andromeda, or M31.
Triangulum, or M33.
The Milky Way.

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6
Q

What do barred spiral galaxies look like?

A

Like a spiral galaxy, except that they have a bright bar from which the spiral arms emerge.

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7
Q

Give an example of a barred spiral galaxy.

A

NGC 1365.

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8
Q

What are lenticular galaxies?

A

A class between ellipticals and spirals.

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9
Q

Give an example of a lenticular galaxy.

A

Spindle Galaxy.

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10
Q

What do elliptical galaxies look like?

A

A relatively smooth spheroidial distribution of stars.

Decrease in brightness from the centre outwards.

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11
Q

Give an example of an elliptical galaxy.

A

M32.

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12
Q

What do irregular galaxies look like?

A

They have very little structure or symmetry.

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13
Q

When and where was Hubble’s Tuning Fork diagram first published?

A

In 1936, in Hubble’s book ‘Realm of the Nebulae’.

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14
Q

What was Hubble’s Tuning Fork diagram originally intended to be?

A

An evolutionary scheme of galaxies (which was later found to be incorrect).

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15
Q

What galaxy type is the Milky Way?

A

An Sb galaxy by tradition. NOT a barred spiral.

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16
Q

Can active galaxies emit other forms of radiation outside visible light?

A

Yes.

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17
Q

What are active galaxies?

A

Extremely distant objects with a highly energetic object at their centre, that emit radiation at wavelengths other than visible light.

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18
Q

If AGNs are indeed variations on the same theme, what could observational differences be due to?

A

Angle at which AGN is observed

Mass of black hole

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19
Q

How do AGNs emit radiations?

A
  1. Cold matter is pulled into a black hole.
  2. Matter is sped up by gravity.
  3. This creates friction.
  4. This creates heat.
  5. This makes it produce X-rays just outside the event horizon.
  6. Leads to the creation of ‘lobes’.
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20
Q

Are AGNs stars?

A

NO!

21
Q

What are the two categories of AG?

A

Radio-loud and radio-quiet.

22
Q

Describe radio galaxies.

A

Elliptical
Emit more than a million times more radio waves than normal galaxies
Have radio lobes

23
Q

When were radio galaxies discovered?

A

In the 1950s.

24
Q

Describe quasars.

A

Extremely redshifted spectral lines suggests that they are some of the most distant objects in the universe
… and also the oldest.
Emit strongly at all regions, but particularly X-rays and radio waves.
Compact appearance makes them look like stars.
Have high luminosities.
Have jets.

25
Q

When were quasars discovered?

A

1963

26
Q

What are blazars?

A

Also have high luminosities.
Also look like stars.
Less distant than quasars.
Emit strongly in all regions of the spectrum, from gamma rays to radio rays.
Can vary dramatically in optical brightness on a timescale of days.

27
Q

When were blazars discovered?

A

In the 1970s.

28
Q

What are Seyfert galaxies?

A

Emit strongly in IR and X-ray regions of the spectrum.
Emissions vary.
Spiral or irregular galaxies.
Have extremely compact and bright nuclei.
Strong emission lines.

29
Q

How many galaxies does the local group contain?

A

Over 50.

30
Q

How large is the local group?

A

3Mpc

31
Q

Where is the gravitational centre of the Local Group?

A

Between the Milky Way and Andromeda galaxy.

32
Q

How many groups are there within 10Mpc of us?

A

5

33
Q

How many galaxies does the Virgo cluster have?

A

2000

34
Q

Where is the centre of the Virgo cluster?

A

15-20Mpc from us

35
Q

How many galaxies does the Coma cluster have?

A

1000

36
Q

How far away is the Coma cluster?

A

100Mpc

37
Q

What is interesting about the Coma cluster?

A

It is dominated by 2 giant elliptical galaxies.

38
Q

Give five facts about the Andromeda galaxy (M31).

A 
Contains 1 trillion stars.
Is a spiral galaxy.
Has 2 black holes at its centre.
It is moving towards us and will collide in 3.75 billion years
The largest galaxy in the Local Group.
Contains 1 trillion stars.
39
Q

Give three facts about the Large and Small Magellanic Clouds.

A

Companion galaxies to the Milky Way.
Irregular galaxies.
The Small Magellanic Cloud is a dwarf galaxy.

40
Q

When were Seyfert Galaxies discovered?

A

In 1943 by Carl Seyfert.

41
Q

Give two facts about the Triangulum Galaxy (M33).

A

A spiral galaxy.

The third largest in the group.

42
Q

Give two examples of dwarf galaxies in the Local Group.

A

Aquarius Dwarf and Pisces Dwarf.

43
Q

Is a group the same as a cluster?

A

No, a group is inferior to a cluster.

44
Q

What is commonly found in the centre of a cluster?

A

A giant elliptical galaxy.

45
Q

Give two facts about clusters.

A

Often dominated by a giant elliptical galaxy.

Named after the constellation in which they lie.

46
Q

What supercluster do we belong to?

A

The Virgo supercluster.

47
Q

How many galaxy groups and clusters does the Virgo supercluster contain?

A

Over 100.

48
Q

How many superclusters are there in the observable universe (approx.)

A

Millions

49
Q

Give 4 components of the Virgo supercluster.

A

Local Group
Fornax Cluster
Coma Cluster
Virgo Cluster

Astronomy GCSE (7 decks)

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