Astrophysics Flashcards

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1
Q

Define a universe

A

Contains everything that there is

Created by the big bang 13.7 billion years ago

expanding faster than the speed of light

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2
Q

Define galaxy

A

10 to the power of 11 in our universe

Collection of billions of stars

We are in the Milky way

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3
Q

Define stars

A

Made of hydrogen

Nuclear fusion of H to He

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4
Q

Define Solar systems

A

Everything that orbits our sun is part of our solar system

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5
Q

What are satellites

A

Anything that orbit a planet

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6
Q

How do satellites orbit

A

Orbit in circles around planets

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7
Q

How do planets orbit

A

Slightly elliptical around stars

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8
Q

How do comets orbit

A

Highly elliptical around stars they speed up when closer due to the gravitational force

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9
Q

Give the weight mass gravity equation

A

w = m x g

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10
Q

Every object has a ……………..field around it. The field strength is………for larger masses.

A

Gravitational

Larger

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11
Q

What is weight measured in

A

N

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12
Q

What is the orbital speed equation

A

v = 2πr ÷ T

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13
Q

Orbital speeds are usually measured in….

A

Km/s

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14
Q

Stars have different……….. , …………and………….

A

Colours, sizes and brightnesses

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15
Q

What are stars grouped by

A

Their colours

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16
Q

What colour will a hot and cold star be

A

Hot = Blue

Cold = Red

17
Q

Describe the birth of a star

A

Nebula = a cloud of gas and dust. It compresses due to gravitational forces that attract all the particles together

Fusion begins = The nebula heats up and pressure increases and starts to glow. This heats up further, eventually at 10 million kelvin, fusion begins

Main sequence stars = when the star becomes stable it’s called a main sequence star
Radiation pressure = gravitational force
H fuses to He

Solar System = Unused material around the star is grouped together to form planets, comets, etc.

18
Q

Describe the life of a star

A

Nebula collapses due to gravity

It heats up and fusion begins
Pressure increases

Main sequence star = stable

Eventually hydrogen runs out, star compresses because gravitational force is greater than radiation pressure. temperature + pressure increase, fusion of helium begins. The star swells to a massive size. The surface is cooler so it appears red.

Eventually helium runs out. Gravitational force dominates again, compressing the star and heating it up but not enough to fuse Carbon. It now glows white and is called a white dwarth. They are millions of times denser than anything on Earth

As the c
dead star cools, the colour changes to black

19
Q

Describe the life of a big star

A

Nebula collapses due to gravity

Heats up,pressure increases and fusion begins

Main sequence star stable due to radiation pressure = gravitational force

When hydrogen runs out the star fuses all the elements up to iron. It swells to an ENORMOUS size called a super Red Giant

When fuel finally runs out it collapses and explodes = Super Nova

The core that remains is EXTREMELY dense!!
Neutron star

If the star was massive the core would be even denser, gravity cannot escape = black hole

20
Q

What two things does the brightness of a star depend on

A

Luminosity (power output)

Distance from Earth

21
Q

The brightness of a star is called it’s…………………..

A

Apparent magnitude

22
Q

What is Absolute Magnitude

A

Compares all the stars as if they would appear at a set distance from Earth

23
Q

Describe the birth of the universe

A

All the matter and all the energy in the universe started from a suer small, hot, dense point called a singularity that suddenly exploded about 13.8 billion years agoIt has been expanding ever since

24
Q

What is the doppler effect

A

if the source of a wave is moving towards us, then the wavelength is compressed. for light waves this is called blue shift. If the source is moving away then the wavelength is stretched and called red shift. This can happen with sound

25
Q

What si the equation for the doppler effect

A

λ - λ
—————– = v/c
λ 0

26
Q

What is C

A

Speed of light

3x10 to the power of 8

27
Q

The faster something moves the greater the…………

A

Red shift