Chapter 8: Space physics

Question 1

How do stars produce their energy?

Answer 1

Nuclear fusion, in which 2 smaller nuclei join to make a larger one, releasing energy. Example: 11H + 21H = 32He

Question 2

What is acceleration?

Answer 2

Acceleration is when either the magnitude or direction of an object change. For example, a car switching from moving at 30 mph to moving at 60 mph, or a car changing direction. The earth, as it orbits the sun, is constantly accelerating, since it is constantly changing direction, but that does not mean it is gaining speed

Question 3

How long ago was the sun formed?

Answer 3

4.6 billion years ago

Question 4

What is a protostar?

Answer 4

Sometimes, clouds made of cold hydrogen and dust collapse due to the force of gravity. This makes the atoms and molecules within the cloud move extremely fast, giving them large amounts of kinetic energy. When they crash into each other, their kinetic energy is turned into heat, increasing the internal energy of the gas, making the temperature rise to millions of degrees

Question 5

How does fusion begin?

Answer 5

The temperate inside the cloud gets so high that the hydrogen nuclei begin to collide, forming helium and releasing energy. This starts a chain reaction

Question 6

What holds a star together?

Answer 6

The outward force of fusion trying to expand a star balances the inward force of gravity trying to collapse a star

Question 7

What is a main sequence star?

Answer 7

One that releases energy by fusing hydrogen to form helium. Our sun is a main sequence star.

Question 8

What is a red giant?

Answer 8

A very large star that fuses helium into heavier elements

Question 9

What are the life paths a low-mass star (such as our sun) can take?

Answer 9

Protostar, Small star, Red giant, white dwarf, black dwarf

Question 10

What are the life paths a high-mass star can take?

Answer 10

Protostar, Large star, Red supergiant, Supernova, and then either a neutron star or a black hole

Question 11

What happens when a star collapses?

Answer 11

When a star begins to run out of hydrogen, it begins to collapse inwards because the force of gravity is no longer balanced out by the force of fusion, heating up the core, making it produce even heavier elements than helium. This makes the star expand into a red giant, where it continues to fuse helium

Question 12

What is velocity?

Answer 12

A vector quantity taking into account both direction and speed

Question 13

How do we know that our earth was once part of another star?

Answer 13

It has elements heavier than iron on it

Question 14

What happens when a small star collapses (from red giant phase)?

Answer 14

When the star runs out of helium, it collapses into a white dwarf, eventually cooling down into a black dwarf, a cold, dark, dead star

Question 15

What happens when a large star collapses (from red supergiant phase)?

Answer 15

When the star runs out of helium, it blows up in a runaway nuclear reaction known as a supernova (in which elements heavier than iron are fused). If the star’s mass is below a certain threshold, it becomes a neutron star. If not, it becomes a black hole

Question 16

Describe a circular orbit

Answer 16

The direction of the object’s velocity is at a tangent to the orbit path. The object accelerates towards whatever it’s orbiting, but doesn’t get any closer to it. Gravity provides the force to accelerate the planet

Question 17

What happens as the planet gets closer to the star it’s orbiting?

Answer 17

It speeds up, since gravity is what provides the force that keeps the object moving

Question 18

What is redshift?

Answer 18

When EM waves coming from a far away object are stretched due to the Doppler effect. We can tell that redshift has occurred because the lines on an emission spectrum are shifted to one end. Redshift was discovered by Edwin Hubble in the 1920s

Question 19

What does redshift tell us about the universe?

Answer 19

It tells us that the universe is expanding

Question 20

What is the Big Bang Theory?

Answer 20

The theory that 13.8 billion years ago, the universe expanded outwards from a singularity and has been expanding ever since. Things further away from the solar system move away faster. The universe expanding is a lot like a balloon being blown up

Question 21

What is CMBR?

Answer 21

CMBR (or cosmic microwave background radiation) is radiation that was released shortly after the creation of the universe

Question 22

How does CMBR support the Big Bang Theory?

Answer 22

Because the Big Bang theory states that at the beginning, a large amount of EM waves were produced (whose wavelengths increased over time, making them microwaves right now). This is supported by the 1960s discovery of CMBR

Question 23

When and why did the Big Bang Theory become widely accepted?

Answer 23

The Big Bang Theory became widely accepted in the 1960s after the discovery of CMBR by 2 scientists

Question 24

Explain the models for the future of the universe?

Answer 24

Up until the 1990s, we believed that the universe would one day stop expanding and collapse again in a “Big Crunch”. With the discovery of dark energy (which is said to be suppressing gravity, we now believe that the rate at which the universe expands is increasing

Question 25

What did the ancients believe about the solar system?

Answer 25

Aristotle believed that the sun, planets and stars orbited the Earth (the Earth and sun’s positions were swapped). He believed that the reason why the planets sometimes appeared to be at different positions relative to the stars was because they travelled at different speeds

Question 26

What did Copernicus suggest?

Answer 26

Copernicus noticed that Aristotle’s model did not properly explain why planets seemed to move backwards and forwards in the sky. Copernicus realised that this can be explained if we put the sun at the centre of the solar system, this would be explained (we overtake Mars around once every year, since it moves slower, meaning that when we do, Mars appears to move in the opposite direction)

Question 27

How did Galileo’s discoveries support this?

Answer 27

Galileo discovered that Mars varies in brightness, Venus has phases like the moon, and Jupiter has 4 moons. This means that the distance between Earth and Mars changes, Venus occasionally disappears behind the sun, and since Jupiter appeared to only have 3 moons on some nights, which appeared to move round it, he believed that Earth moved too

Question 28

What is a comet?

Answer 28

A comet is a small icy body in an eccentric orbit around the sun. Comets sometimes have tails

Question 29

What is a meteor?

Answer 29

A meteor is a meteoroid that is burning up in the Earth’s atmosphere

Question 30

What is a meteorite?

Answer 30

A meteorite is a meteoroid that successfully reaches the Earth’s surface

Question 31

What is a meteoroid?

Answer 31

A meteoroid is a small rocky piece debris (up to 10 metres wide) that is floating around in space

Question 32

What is the main sequence?

Answer 32

In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness

Question 33

How is evidence for the early solar system gathered?

Answer 33

UUHHH

Question 34

Why are elements heavier than iron not fused in normal stars?

Answer 34

Because it is not favourable for a star to fuse elements heavier than iron, since it would require more energy than it would give back (would only occur in a supernova)

Question 35

Why is Pluto categorised as a dwarf planet?

Answer 35

Another planet was found behind it in 2005, so it became classified as a dwarf planet

Question 36

Describe our galaxy

Answer 36

Our galaxy is a whirlpool with spiral arms. The sun takes 220 million years to make one full orbit of the black hole at the centre of our galaxy