Space physics

Question 1

What is a mnemonic to remember the order of the planets in the solar system?

Answer 1

My - Mercury
Very - Venus
Enthusiastic - Earth
Mother - Mars
Just - Jupiter
Served - Saturn
Us - Uranus
Nine - Neptune
Pizzas - Pluto

Question 2

What is within our solar system?

Answer 2

one star (the Sun), eight planets, the dwarf planets (including Pluto), and natural satellites (moons that orbit planets)

Question 3

What is our solar system a small part of?

Answer 3

The Milky Way Galaxy

Question 4

How do stars form?

Answer 4

• stars form from a cloud of dust and gas (nebula)
• gravity causes the cloud of gas and dust to collapse (collapsing cloud of hot gas and dust is a ‘protostar’) => as the dust particles move faster, temperature rises to millions of degrees celsius
• if the temperature of the protostar gets high enough, then hydrogen nuclei join together to form helium (process is called nuclear fusion) => protostar => star

Question 5

What does nuclear fusion release?

Answer 5

a huge amount of energy

Question 6

What happens a star that is undergoing nuclear fusion?

Answer 6

There are two opposing forces acting within the star:

• force of gravity acts inwards => causes the star to collapse
• energy from nuclear fusion creates a force acting outwards => causes the star to expand

Question 7

What forces are balanced?

Answer 7

• the force of gravity acting inwards is balanced by the force due to fusion energy acting outwards

=> star is in equilibrium

Question 8

What is a star’s life cycle determined by?

Answer 8

the size of the star

Question 9

What happens in a main-sequence star when the hydrogen begins to run out?

Answer 9

• the outward force due to fusion energy is less than the inward force due to gravity => star collapses inwards => temperature increases =>
  helium nuclei fuse together to create heavier elements => star expands to form a red giant

Question 10

What happens when a red giant stops fusing helium?

Answer 10

• star shrinks and forms a whte dwarf (no longer carrying out fusion so it gradually cools down)

Question 11

What is formed when a white dwarf eventually stops releasing any energy?

Answer 11

• when the white dwarf stops releasing any energy, a black dwarf is formed

Question 12

What happens when a star, that is much bigger than our Sun, runs out out hydrogen?

Answer 12

• they leave the main-sequence stage and expand into red super giants

Question 13

What is similar with smaller stars like the Sun and the red super giants?

Answer 13

• helium nuclei fuse together to produce heavier elements

Question 14

What is the heaviest element that nuclear fusion can make with a star that is the same size as the Sun?

Answer 14

• nuclear fusion cannot make elements heavier than iron

Question 15

What happens when red super giants stop carrying out nuclear fusion?

Answer 15

• the star explodes => supernova

Question 16

How can supernovas create elements heavier than iron?

Answer 16

• temperature of a supernova is high enough to produce elements heavier than iron (when the supernova explodes, these elements are distrubed throughout the Universe)

Question 17

What 2 objects can form after a supernova?

Answer 17

• neutron star
• black hole

Question 18

What does a neutron star consist of?

Answer 18

• neutrons densely packed together

Question 19

What is special about a black hole?

Answer 19

• a black hole has such a large gravity that not even light can escape

Question 20

What is it called when the Earth rotates around the Sun?

Answer 20

• a circular orbit as the Earth follows the path of a circle around the Sun

Question 21

What is the more realistic orbit called?

Answer 21

• elliptical orbit

Question 22

How do planets and satellites maintain their circular orbits?

Answer 22

• gravity provides the force (e.g. the force of gravity acting between the Sun and the Earth holds the Earth in its orbit)

Question 23

Give an example of a natural satellite?

Answer 23

• the Moon is a natural satellite

Question 24

Give an example of an artifical satellite?

Answer 24

• the International Space Station

Question 25

What is the difference between artifical satellites and natural satellites?

Answer 25

- artificial satellites are man-made that can be used to study the Earth, other planets, to help us communicate, and even to observe the distant Universe

Question 26

What are geostationary satellites? What does this mean about their position to the Earth?

Answer 26

- geostationary satellites orbit once every 24hours - as the Earth takes 24hours for one full spin, the geostationary satellites always point to the same part of the Earth

Question 27

Why does the force of gravity acting on satellites lead to a change in velocity but not a change in speed?

Answer 27

- velocity is a vector quantity (involves magnitude AND DIRECTION) so the direction is always changing but the speed remains constant

Question 28

What happens to the radius of a satellite's orbit is the speed increases? Why does this happen? What does this relationship lead to?

Answer 28

- if a satellite orbits at an increased speed, then the radius of the satellite's orbit decreases - at a greater speed, the satellite needs a greater force of gravity to prevent it flying off into space (satellite comes closer to the Earth) => stable orbit

Question 29

In the 1900s, what did astronomers detect about the light from distant galaxies?

Answer 29

- they detected that the light from very distant galaxies had an increased wavelength compares to light from closer galaxies

Question 30

On a spectrum, how can we identify absorbed wavelengths?

Answer 30

- certain elements absorb light of specific wavelengths => those specific wavelengths appear as dark, vertical lines

Question 31

On a spectrum of light from a distant galaxy, what will we notice about the absorbed wavelengths of light? What do scientists call this effect?

Answer 31

- all the lines will have shifted slightly towards the red end of the spectrum (red-shift)

Question 32

What does the red-shift tell us?

Answer 32

- galaxies are moving away from each other (observed wavelength is increased)

Question 33

How can we identify fast-moving galaxies?

Answer 33

- galaxies that are further away have a bigger red-shift so these galaxies are moving faster than galaxies that are closer

Question 34

What does red-shift provide evidence for?

Answer 34

- the fact that distant galaxies are moving faster than nearby galaxies provides evidence tat hee universe is expanding (supports The Big Bang theory)

Question 35

What do scientists believe about The Big Bang theory?

Answer 35

- scientists believe that the universe began from a very small region that was extremely hot and dense...which expanded into the universe we see today

Question 36

What did observations of supernovae sugest?

Answer 36

- scientists used to think that due to gravity, the expansion of the Universe would slow down - observations of supernovae suggest that distant galaxies are actually receding increasingly faster

Question 37

Give 2 examples of what is still not understood about the Universe.

Answer 37

- dark mass/matter - dark energy