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IGCSE Physics > Astrophysics > Flashcards

Astrophysics Flashcards

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1
Q

What is the universe?

A

A large collection of billions of galaxies.

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2
Q

What is a galaxy?

A

A large collection of billions of stars.

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3
Q

What is a solar system?

A

A collection of planets orbiting a common star.

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4
Q

Where is our solar system?

A

On a spiral arm of the milky way galaxy.

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5
Q

What do comets orbit?

A

Stars, eg the Sun

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6
Q

Describe the orbit of comets:

A

Very elliptical orbit shape, with the star near one end
Longer orbital period than Earth
Travels much faster when it’s nearer the star due to increased pull of gravity

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7
Q

What do moons orbit?

A

Planets

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8
Q

Describe the orbit of moons:

A

Slightly elliptical

Near constant orbital speed

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9
Q

What do planets orbit?

A

Stars, eg the Sun

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10
Q

Describe the orbit of planets:

A

Slightly elliptical

Near constant orbital speed

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11
Q

Equation to show relationship between orbital speed, orbital radius and time period:

A

orbital speed = (2 x pi x orbital radius) / time period

v = 2 x pi x r / T

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12
Q

What is the stellar evolution for stars a similar size to our Sun?

A
  1. Nebula
  2. Protostar
  3. Main sequence star
  4. Red giant
  5. White dwarf
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13
Q

What is the stellar evolution for stars bigger than our Sun?

A
  1. Nebula
  2. Protostar
  3. Main sequence star
  4. Red supergiant
  5. Supernova
  6. Neutron star or black hole
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14
Q

What is a nebula?

A

A cluster of dust and gas in space

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15
Q

What is a protostar?

A

Force of gravity pulls the dust and gas together to form a protostar. When the temperature is high enough, nuclear fusion starts. This releases energy, keeping the core hot.

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16
Q

What is a main sequence star?

A

The star enters a long stable period. The force of gravity holding the star tightened is balanced by high pressure due to the high temperatures.
Our sun is at this phase. The main sequence phase lasts about 10 billion years.

17
Q

What is a red giant/ supergiant?

A

When all the hydrogen has been used up in the nuclear fusion process larger nuclei begin to form and the star may expand to become a red giant.

18
Q

What is a white dwarf?

A

When the red giant becomes unstable and ejects its outer layer of dust and gas, leaving behind a hot, dense solid core, a white dwarf

19
Q

What is a supernova?

A

The star will go on making nuclear reactions, getting hotter and expanding until it explodes as a supernova.

20
Q

What is a neutron star?

A

The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star.

21
Q

What is a black hole?

A

If a neutron star is massive enough, it will collapse and become a black hole.

22
Q

What is absolute magnitude?

A

The apparent magnitude (brightness) of a star if it were viewed from exactly 10 parsecs away (32.6 light years).

23
Q

What affects the brightness of a star?

A

In general, the bigger and hotter the star, the brighter it is.

24
Q

What is a parsec?

A

Unit of distance

3.26 light-years

25
Q

What does a Hertzsprung-Russell diagram show?

A

Relationship between a star’s surface temperature and brightness
Magnitude scale from -15 (brightest) to +10

26
Q

What are the main components on an HR diagram?

A

Supergiants
Red giants
The main sequence
White dwarfs

27
Q

Where are supergiants on a HR diagram?

A

Top right

28
Q

Where are red giants on a HR diagram?

A

Top right, below supergiants

29
Q

Where are main sequence stars on a HR diagram?

A

Diagonal strip from top left to bottom right

30
Q

Where are white dwarfs on a HR diagram?

A

Bottom left

31
Q

What does the Big Bang theory state?

A

The universe expanded outwards from a single point in space in time.

32
Q

How does redshift support the Big Bang theory?

A

The redshift of light from other galaxies shows that they are all moving away from us, those which are furthest away are moving the fastest.
Suggests universe was formed from an explosion at a single point.

33
Q

How does the presence of CMBR support the Big Bang theory?

A

Just after the Big Bang, lots of short wavelength radiation would have been released. As the universe expanded over time, this would have been stretched to become microwaves.
It is present in all directions, wherever you point a telescope in the sky.

IGCSE Physics (6 decks)

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