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Physics GCSE > Astronomy > Flashcards

Astronomy Flashcards

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1
Q

Order of the solar system

A

Sun
Mercury
Venus
Earth
Mars
Asteroid belt
Jupiter
Saturn
Uranus
Neptune

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2
Q

Weight =

A

Mass (kg) x gravitational field strength (N)

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3
Q

How was Ptolemy model of the solar system different to the one of the modern day

A

He placed Earth at the centre of the universe

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4
Q

Who changed Ptolemy’s model to having the sun at the centre of solar system

A

Nicolas Copernicus

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5
Q

What is Newton’s first law

A

An object travelling g at a certain velocity will continue to travel at that velocity unless acted upon by a resultant force

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6
Q

Define solar system

A

The collection of eight planets and their moons in orbit around the sun

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7
Q

What was ptolemys model called

A

The geocentric model (2nd century AD)

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8
Q

Who invented the telescope

A

Galileo Galilei (1564-1642)

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9
Q

When was Galileo’s telescope invented

A

1604

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10
Q

What was Copernicus’ model of the solar system

A

Heliocentric circles positioned the sun at the centre of the universe with the planets orbiting around it in circular paths, modified by epicycles & at uniform speeds.

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11
Q

What did Galileo see with his new invention

A

He was able to look at the moon, observe a supernova, verify the phases of Venus and discover sunspots.
His discoveries proved the copernican system.

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12
Q

What is the only force acting on the moon

A

Gravity

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13
Q

What are the uses of artificial satellites

A

Photography
communication
weather forecasting
GPS
spying
Wi-Fi
service

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14
Q

What are polar orbits used for

A

Weather forecasting

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15
Q

What are Geostationary orbits used for

A

Communications

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16
Q

What is the difference etc between a geostationary orbit and a polar orbit

A

The satellites in polar orbits travel very close to the earth (200km above sea level) so they must travel at very high speeds (nearly 8000m/s) to stay in orbit.
The satellites in geostationary orbits take about 24hours to orbit the earth. These orbits are much higher than polar orbits (36000km) so the satellites travel slower (3km/s)

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17
Q

What shape are the orbits of comets

A

Elliptical

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18
Q

What is a comet

A

Made from rocky material, dust and ice
Orbits the sun

19
Q

How is weight affected by different planets

A

Weight is proportional to the gravitational field strength of the planet

20
Q

What happens to the speed and the velocity of a planet in circular orbit

A

The speed remains constant but the velocity changes as the direction is changing

21
Q

Why doesn’t the moon fall down

A

Gravity is the only force that acts on the moon.
The moon will always accelerate towards the centre of the Earth (centripetal force)
The force of gravity is at right angles to the motion and remains this way so the moon moves in a curved path

22
Q

What causes an object in orbit to accelerate

A

When an object moves in a circle at a constant speed, direction constantly changes.
A change in direction causes a change in velocity. This is because velocity is a vector quantity.
The change in velocity results in acceleration, so an object moving in a circle is accelerating even though its speed may be constant.
However an object will only accelerate if a resultant force acts on it (eg. Centripetal force)

23
Q

Explain red-shift

A

Light from a star does not contain all the wavelengths of the electromagnetic spectrum (they absorb some of the wavelengths) so absorption lines appear.
Red-shift is when the wavelengths of light are stretched and so the absorption lines move closer to the red end of the spectrum.
This proves that the universe is expanding

24
Q

What is the Steady State Theory

A

Says that the universe has always existed and the universe is expanding and constantly CREATING MATTER AS THE UNIVERSE EXPANDS

25
Q

What is cosmic microwave background radiation

A

Comes from all directions in space.
It is the remains of the thermal energy from the Big Bang spread thinly across the whole universe

26
Q

Why do we put telescopes on satellites

A

Being above the atmosphere allows them to detect x-rays and gamma rays etc as the ozone layer does not allow all wavelengths of light through

27
Q

How do stars begin their lives

A

As a cloud of dust and gas (NEBULA) mostly composed of hydrogen.

28
Q

What causes a nebula to become a protostar

A

Gravity begins to pull the dust and gas together and as the mass falls together it gets hot (gravitational collapse)

29
Q

What happens after a nebula

A

A PROTOSTAR is formed when it is hot enough for the hydrogen nuclei to fuse together to make helium
The fusion process releases energy which keeps the core of the star hot

30
Q

What happens to low & medium mass stars in the main sequence stage of their life

A

This is the STABLE PHASE in the life of a star where it spends 90%of its life
Hydrogen fusion is happening producing helium in the core of the star

31
Q

What causes the change to a red giant

A

Star runs out of hydrogen in its core

32
Q

What happens in a red giant

A

When a star has fused all the hydrogen nuclear radiation ceases and so star starts to collapse due to gravity.
Hydrogen in the surrounding stellar atmosphere is burnt due to the intense heat generated by the core.
This causes the outer layers to expand and cool down

33
Q

What happens to a red giant in order for it to become a planetary nebula

A

Star core continues to heat which allows helium fusion to take place

34
Q

What a happens in a planetary nebula

A

Once all the helium is used up and because the core will never get hot enough for further fusion it expels the outer layers of gas in an explosion called a planetary nebula 

35
Q

What is a white dwarf

A

A tiny core compromising primarily of carbon and oxygen
It is condensed to the size (roughly) of the Earth due to the pressure exerted by fast moving electrons

36
Q

What does a planetary nebula explosion leave behind

A

A white dwarf

37
Q

What is a black dwarf

A

Remains of a white dwarf .
As the white dwarf cools and burns all remaining fuel it will continue to dim until they are no longer visible to us.

38
Q

What happens to high mass stars in the main sequence stage of their life

A

They use up hydrogen very quickly and exit the main sequence after only a few million years

39
Q

What causes a red supergiant

A

The core temperatures are so high that nuclear fusion can occur even after the helium has been exhausted

40
Q

What happens in a red supergiant

A

Nuclear fusion continues in the core until iron is formed as no further fusion can occur after this as fusing iron consumes more energy than it releases

41
Q

What causes a supernova

A

Star collapses instantly under the enormous gravity exerted on a heavy iron core.
The core reduces to a couple of miles in a matter of seconds and the collapses triggers an explosion called a supernova
The energy released is so great that iron fusion can occur and all heavier elements are created

42
Q

What causes a neutron star

A

If the collapsing supernova leaves a core behind of 1.4-3 solar masses it forms a neutron star.
Here the force of gravity on the collapsing core is so large that the negatively charged electrons are pushed to combine with the protons to form neutrons in the nucleus

43
Q

What causes a black hole

A

If the supernova leaves behind a core of more than 3 solar masses such a big mass collapses to a point known as a singularity.
There the gravitational force is so strong that nothing escape it. 

44
Q

Which two things balance and keep a main sequence star in equilibrium

A

Gravity and radiation pressure

Physics GCSE (17 decks)

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