Topic 8 - Space

Question 1

What is a satellite?

Answer 1

they orbit a planet - can be natural or artificial

Question 2

What is an asteroid?

Answer 2

a small rocky object that orbits the sun

Question 3

Where does the asteroid belt lie?

Answer 3

between Mars and Jupiter
(between the rocky and gas planets)

Question 4

What is a comet?

Answer 4

made of ice and dust and have a very elliptical orbit around the sun

Question 5

What is a galaxy?

Answer 5

a massive collection of billions of stars

Question 6

What is the universe?

Answer 6

contains lots of galaxies and is mostly empty space

Question 7

Describe a nebula

Answer 7

a giant cloud of hydrogen gas and dust - the first stage of a star

Question 8

How does a nebula form a protostar?

Answer 8

the force of gravity pulls the particles closer together until it forms a hot ball of gas (protostar)

Question 9

How does a protostar form a main sequence star?

Answer 9

• it continues to pull particles in which increases the density and temperature
• this means more nuclear fusion will occur and it will become a main sequence star

Question 10

Why does a main sequence star remain stable for a long time?

Answer 10

the outward pressure force (from fusion reactions) is equal to the inward force due to gravity

Question 11

How does a red giant become a white dwarf?

Answer 11

• the star becomes unstable and ejects the outer layer of dust and gas (called a planetary nebula)
• the core collapses (due to gravity) and it’s a white dwarf

Question 12

How does a main sequence star become a red (super) giant?

Answer 12

• the star runs out of hydrogen so there are fewer fusion reactions
• the core shrinks because the inward gravity force is now stronger than the outward force
• fusion begins again and causes the outer part of the star to expand

Question 13

How does a white dwarf become a black dwarf?

Answer 13

the white dwarf is emitting lots of energy (light) and becomes cooler and darker and becomes a black dwarf

Question 14

How does a red super giant become a supernova?

Answer 14

once the fusion reactions finish, the core collapses suddenly, causing a huge explosion - called a supernova

Question 15

How does a supernova become a neutron star / a black hole?

Answer 15

• a dense neutron star will form in a supernova
• if the star is massive, the neutron star will continue to collapse (due to gravity) and forms a black hole

Question 16

Which main sequence stars become red giants and which become red super giants?

Answer 16

• small/ medium (sun size) - red giant
• big (bigger than sun) - red super giant

Question 17

What is the complete life cycle of a star that’s a similar size to the sun?

Answer 17

• nebula
• protostar
• main sequence star
• red giant
• white dwarf
• black dwarf

Question 18

What is the complete life cycle of a star that’s bigger than the sun?

Answer 18

• nebula
• protostar
• main sequence star
• red super giant
• supernova
• neutron star / black hole

Question 19

What elements are formed in the fusion reaction in a main sequence star?

Answer 19

hydrogen nuclei fuse to form helium nuclei

Question 20

What elements are formed in fusion reactions in red (super) giants?

Answer 20

helium nuclei will fuse to form elements lighter than iron

Question 21

What elements are formed in fusion reactions in supernovas?

Answer 21

forms elements heavier than iron

Question 22

Define an orbit

Answer 22

the curved path of one celestial object around another celestial object

Question 23

What are the 2 forces acting on Earth when it’s orbiting the sun?

Answer 23

• gravity (pulling towards the sun)
• instantaneous velocity (moving forward)

Question 24

Why is the earth constantly accelerating?

Answer 24

• it has a circular orbit so it’s constantly changing direction
• this means it’s velocity is constantly changing
• changing velocity = acceleration

Question 25

Which planets travel at the fastest speeds?

Answer 25

the planets with a smaller orbit travel at the fastest speed because gravity is stronger so the speed must be faster so the planet can continue in it’s orbit

Question 26

Describe how red shift works

Answer 26

• when light from the sun reaches the earth, certain wavelengths are missing
• light from other galaxies also have missing wavelengths, but shifted towards the red end of the spectrum (light waves get stretched as they travel to Earth)
• this indicates galaxies are moving away from us

Question 27

The further away a galaxy is …

Answer 27

the faster it’s moving away from us

Question 28

Why specifically are galaxies moving away from us?

Answer 28

the space between us and the galaxy is expanding

Question 29

Describe the big bang theory

Answer 29

• around 14 billion years ago, all the matter was in a very small, dense region
• series of explosions, called the Big Bang
• caused the universe to expand, and it continues to do so

Question 30

How is redshift evidence for the Big Bang?

Answer 30

• redshift proves that galaxies are moving further away from each other (because the light waves are stretched)
• proves the universe is expanding and if it’s expanding, it must’ve started very small