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GCSE Edexcel Astronomy > (A) Topic 14, 15,16 Wrongs > Flashcards

(A) Topic 14, 15,16 Wrongs Flashcards

1
Q

What kind of objects are in the Messier catalogue?

A

Objects that initially looked like comets but weren’t

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2
Q

What is the New General Catalogue and how are objects labelled in it?

A

List of galaxies, star clusters, emission and absorption nebulae catalouged by number. They have the prefix NGC

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3
Q

Explain how stars are labelled in a constellation on a star map.

A

Bigger dots = larger stars, smaller dots = smaller stars

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4
Q

What is the Bayer Designation?

A

Classification system for stars after their brightness where each letter has a Greek letter in lower case followed by its Latin name of the constellation

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5
Q

What is some common criticism about the Bayer Designation system?

A
  • doesn’t take into account changes in brightness due to variability
  • alpha star is sometimes not the brightest star
  • changes in constellation boundaries have led to confusion
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6
Q

Why are stars stable?

A

Due to gravity and pressure

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7
Q

What specific pressure is this in main sequence stars and where does it come from?

A

Radiation pressure comes from nuclear reactions in the core. It balances the immense gravity from the star’s mass

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8
Q

What is the white dwarf and what keeps it stable?

A

Stars that have burnt up all of the hydrogen they once used as fuel - are in their last stages of evolution. Electron degeneracy keeps it stable

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9
Q

Define the Chandrasekhar limit.

A

The maximum mass of a white dwarf star. 1.4 solar masses

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10
Q

What keeps a neutron star stable?

A

Neutron pressure

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11
Q

How is a black hole formed?

A

A supergiant star with an iron core collapses due to the collapse of radiation pressure, forming a black hole

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12
Q

What are white giants?

A

Rare stars that evolved from larger and hotter stars that have mostly used their hydrogen

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13
Q

What are black dwarfs theorised to be?

A

White dwarf that has cooled to the extent that it emits no light or heat

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14
Q

What are emission nebulae and how does it emit radiation?

A

Clouds of high temperature as that emit their own light at optical wavelengths. Stars inside or near the nebulae warm the gas through UV radiation, causing the electrons to ionise + emit radiation

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15
Q

What are absorption nebulae?

A

A mass of interstellar gas and dust that absorbs most or all light from star

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16
Q

What are the main sequence stars?

A

Majority population of stars we observe, between brighter and hotter white stars to dimmer and cooler red stars

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17
Q

What are planetary nebulae?

A

The outer layers of an expanding red giant which are visible as an expanding sphere

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18
Q

Describe what happens on the red giant stage.

A
  • slows its rate of fusion
  • lacks outward pressure needed to maintain size
  • increases in size until it starts consuming heavier elements
  • when it runs out of fuel it shrinks to a white dwarf
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19
Q

What occurs in the white dwarf stage?

A
  • shed outer layers
  • starts to collapse under its own gravity then shrinks to white dwarf
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20
Q

What are the two types of supernovas?

A

1) Star takes mass from a giant then explodes
2) Red giants core with a mass greater than several solar masses collapses in on itself

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21
Q

What are the two formations of the neutron star?

A

1) Star between 4-25 solar masses will grow to a red supergiant, explode then form a neutron star
2) White dwarf which can’t contain its mass through electron degeneracy and exceeds 1.4 solar masses

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22
Q

How do neutron stars act?

A

Rotate rapidly after formation, typically spinning between fractions of a second to half a minute

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23
Q

What techniques have scientists used to discover neutron stars?

A

They emit radio pulses, the ones we detect are known as pulsars

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24
Q

What are black holes?

A

A region of space having a gravitational field so intense no matter or radiation can escape

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25
Q

What evidence is there for the existence of a black hole?

A

Binary stars that get their solar material pulled into the hole forms an accretion disc

26
Q

What is an event horizon?

A

A notional boundary around a black hole beyond which no light or other radiation can escape

27
Q

Why do we use 21 cm radio wavelengths to measure the galaxy’s rotation?

A

21 cm range is known as the Hydrogen line which allows us to see past clouds of interstellar cosmic as and dust

28
Q

How long does it take for the sun to orbit our galaxy?

A

226 million years

29
Q

Describe the location of the Sun in the Milky Way

A

Positioned on spiral arm called the Orion Arm

30
Q

What is the width of the Milky Way in light years?

A

100,000 - 150,000 light years across

31
Q

What is its height along the plane of the Milky Way?

A

1500 light year

32
Q

Name some of the galaxies in the Local Group

A
  • andromeda
  • Triangulum
  • small and large Magellanic
33
Q

What are superclusters?

A

A large group of smaller galaxy clusters or galaxy groups

34
Q

Explain how the galaxies are classified in the Tuning Fork diagram.

A

Elliptical - prefix E with numbers, as numbers increase, so does the eccentricity of the spiral
Spiral - prefix S with a lowercase letter
same applies to spiral barred

35
Q

What is an AGN?

A

Active galaxy nucleus at the centre of an active galaxy that has above average luminosity

36
Q

How do astronomers find evidence for AGNs?

A

The amount of material around the black hole forms an accretion disc

37
Q

What types of radiation can certain galaxies emit?

A

Radio and X ray

38
Q

Describe a Seyfert galaxy

A
  • bright nuclei
  • emit strongly in IR, UV and X ray regions
  • typically spiral and irregular
39
Q

Describe a Quasar galaxy

A
  • emit strongly in radio waves, UV and X ray regions
  • extremely large black holes
  • furthest + oldest objects we know of
  • moving away from us at fast rates - large redshifts
40
Q

Describe Blazer

A

Compact quasars in which the galactic jets are pointing towards us

41
Q

What are the two main theories about galaxy formation?

A
  • vast clouds of gas + dust collapsed gravitationally allowing stars to be formed
  • lumps of matter present in the Universe clumped together under gravitational influence to form galaxies
42
Q

What are ‘mergers’?

A

Galaxies that merge together to create larger galaxies + increase star formation

43
Q

Which galaxies are thought to be formed first?

A

Galaxies with high populations of red stars

44
Q

How do we know that light from distant galaxies is shifted to longer wavelengths?

A

They emit more red shift - red has a longer wavelength - redshift

45
Q

What is radial velocity?

A

How fast an object is travelling in the direction of the line of sight

46
Q

What is the evidence used to justify that the universe is expanding?

A

Distant galaxies are moving away from us

47
Q

Why is the value of the Hubble constant significant?

A

It allows scientists to take accurate measurements of the Universe

48
Q

Describe Hubble’s law in a sentence.

A

How fast a galaxy moves is proportional to its distance

49
Q

What is the steady state theory?

A

A theory that claims the Universe has always existed and is expanding and constantly creating matter as it expands

50
Q

Describe what is thought to have occurred in the first stages of the Big Bang.

A

Matter, antimatter, hydrogen and helium were created

51
Q

Describe arguments both in favour of and against the Big Bang.

A

favour: - galaxies are moving away from each other
- quasars - fast moving objects formed early on
- CMB leftover heat from the Big Bang
-cons: what caused it?
- not enough mass in the universe to account for all the expansion

52
Q

What are quasars?

A

Astronomical objects with high luminosity is found in the centre of some galaxies and powered by gas spiralling at high velocity in a supermassive black hole

53
Q

How did we discover quasars?

A

First identified thanks to their high red shift and emission of radio waves

54
Q

What is special about quasars?

A

Brightest objects in the universe

55
Q

What did the Hubble space telescope provide information about?

A

Evidence of the early universe after the big bang

56
Q

What is CMB?

A

Cosmic background radiation is the heat remanent of the big bang

57
Q

How was CMB discovered?

A

A sensitive radio telescope was made which eliminated all radio waves but still detected a faint consistent noise

58
Q

What is the difference between dark matter and dark energy?

A

Dark matter pulls galaxies together whereas dark energy pulls them apart

59
Q

What kind of matter we know about could make up what we think might be dark matter?

A
  • dark dust
  • black holes
  • brown dwarfs
  • neutrinos
60
Q

Why do cosmologists believe that dark matter and dark energy exist?

A

The expansion of the Universe should’ve decreased after the big bang but it is increasing, which is evidence of some other force at play

61
Q

What are the main scientific reasons why cosmologists cannot agree on a definite past and future model of the universe?

A
  • Due to religious beliefs
  • many crucial questions have been left unanswered
  • proposition of a multiverse
62
Q

What are some popular models of the universe?

A
  • Big Rip: universe continues to expand but expansion is so strong that it overcomes the gravity within it, atoms get torn apart
  • Big Freeze: universe continues to expand but no new material for star formations exists, and no energy or heat is available
    -Big Crunch: universe stops expanding and starts contracting into a singularity

GCSE Edexcel Astronomy (22 decks)

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