Space

Question 1

what is 1 terametre in metres?

Answer 1

1 * 10^12 metres

Question 2

what is a galaxy?

Answer 2

A cluster of billions of stars, held together by gravity.

Question 3

what happens as the distance from the Sun increases?

Answer 3

• the temperature decreases
• the time taken to orbit the Sun increases

Question 4

what must happen for a planet to form?

Answer 4

• its own gravity must be strong enough to make it round or spherical in shape
• its gravitational field must be strong enough to ‘clear the neighbourhood’, pulling smaller nearby objects into its orbit.

Question 5

what are moons?

Answer 5

natural satellites that orbit a planet

Question 6

what are dwarf planets?

Answer 6

Celestial bodies that orbit the Sun and are spherical in shape but have not cleared their orbit of other debris.

Question 7

what are asteroids?

Answer 7

Small rocky objects that orbit the Sun in highly elliptical orbits which may take millions of years to complete

Question 8

name 2 asteroid belts in our solar system

Answer 8

• asteroid belt between Mars and Jupiter
• Kuiper Belt beyond neptune

Question 9

what are comets?

Answer 9

Small celestial bodies made of ice, dust, and rocky material that orbit the Sun.

Question 10

what happens as a comet approaches the sun?

Answer 10

The comet’s ice begins to vaporize, creating a glowing coma and tail.

Question 11

how did the sun form?

Answer 11

• a large cloud of dust & gas (nebula) collapsed under its own gravity, transferring gravitational potential energy to kinetic energy in its particles
• As the nebula collapsed it became denser, & rotated more rapidly.
• Collisions between particles caused kinetic energy to be transferred as internal energy & thermal energy.
• The core of the nebula began to form a hot, dense protostar.
• When the Sun’s core became hot enough & dense enough, nuclear fusion reactions began.

Question 12

what happens in nuclear fusion reactions in the sun’s core?

Answer 12

• hydrogen nuclei join together to form helium nuclei
• energy is transferred by radiation

Question 13

what do we mean when we say the sun is a star at equilibrium?

Answer 13

it is in a stable state where the inward force of gravity is balanced by the outward force of radiation pressure from the nuclear reactions - the gravitational collapse is balanced by the expansion due to fusion energy.

Question 14

For an object to remain in a steady, circular orbit what must it be doing?

Answer 14

be travelling at the right speed

Question 15

what will happen if a satellite is moving too quickly?

Answer 15

• the gravitational attraction between the Earth and the satellite is too weak to keep it in orbit so it will move off into space.
• This occurs at speeds around or above 11,200 metres per second (m/s).

Question 16

what will happen if a satellite is moving too slowly?

Answer 16

• the gravitational attraction between earth and the satellite will be too strong, and the satellite will fall towards the Earth.
• This occurs at speeds below 7600 m/s.

Question 17

how does orbital motion create acceleration?

Answer 17

• its direction constantly changes as it is in a circle
• a change in direction causes a change in velocity because velocity is a vector quantity so has an associated direction as well as a magnitude.
• A change in velocity results in acceleration, so an object moving in a circle is accelerating even though its speed may be constant.
• But an object will only accelerate if a resultant force acts on it and for an object moving in a circle, this resultant force is the centripetal force that acts towards the middle of the circle.

Question 18

why do objects in small orbits travel faster than objects in large objects?

Answer 18

• The gravitational attraction between two objects decreases with distance.
• therefore, the closer the two objects are to each other, the stronger the force of gravity between them and if the force between them is greater, a greater acceleration will occur.
• The greater the acceleration, the greater the change in velocity - this causes the object to move faster.

Question 19

what is a polar orbit?

Answer 19

an orbit that passes over or near the Earth’s poles

Question 20

what is a geostationary orbit?

Answer 20

Orbit in which a satellite orbits the Earth at the same rate as the Earth rotates (24 hours to orbit), allowing it to remain stationary relative to a fixed point on the Earth’s surface and appears to remain in the same part of the sky when viewed from the ground.

Question 21

why must satellites in polar orbits travel at faster speeds than satellites in geostationary orbits?

Answer 21

The satellites travel very close to the Earth so must travel at very high speeds to maintain their orbit, whereas geostationary orbits are much higher so the satellites travel more slowly

Question 22

what are satellites in polar orbits used for?

Answer 22

monitoring weather, military, taking pictures of the earth’s surface

Question 23

what are satellites in geostationary orbits used for?

Answer 23

communications

Question 24

summarise the life cycle of a star about the same size as the sun

Answer 24

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

Question 25

summarise the life cycle of a star much bigger than the sun

Answer 25

• nebula
• protostar
• main sequence star
• red super giant
• supernova
• either a black hole or neutron star

Question 26

what is a nebula?

Answer 26

massive clouds of dust and gas in space, mostly composed of hydrogen.

Question 27

how does a nebula become a main sequence star?

Answer 27

• Gravity pulls the dust and gas of the nebula together
• As the mass comes together it gets hot. A star is formed when it is hot enough for the hydrogen nuclei to fuse together to make helium - this releases energy, which keeps the core hot.
• the force of gravity holding the star together is balanced by higher pressure due to the high temperatures.

Question 28

how does a main sequence star become a black dwarf?

Answer 28

• When all the hydrogen has been used up in the fusion process in star’s core, larger nuclei begin to form and the star may expand to become a red giant.
• When all the nuclear reactions are over, the star begins to contract under the pull of gravity.
• The star becomes a white dwarf which fades and changes colour to black as it cools.

Question 29

how does a main sequence star become a neutron star or black hole?

Answer 29

• When all the hydrogen has been used up in the fusion process in star’s core, larger nuclei begin to form and the star may expand to become a red giant.
• the star goes on making nuclear reactions, getting hotter and expanding until it implode explodes as a supernova, throwing hot gas into space
• Depending on the mass at the start of its life, a supernova will leave behind either a neutron star or a black hole.

Question 30

what is emission spectra?

Answer 30

• Light from a star does not contain all the wavelengths of the electromagnetic spectrum.
• Elements in the star absorb some of the emitted wavelengths, so dark lines are present when the spectrum is analysed.
• Different elements produce different patterns of dark lines.

Question 31

what is the doppler effect?

Answer 31

an apparent change in frequency of a wave in relation to an observer who is moving relative to the wave source.

Question 32

what is red-shift?

Answer 32

Phenomenon where light from distant galaxies shifts towards longer (redder) wavelengths as they are moving away from the Earth

Question 33

what is the big bang theory?

Answer 33

The scientific theory that suggests all the matter in the universe began as a singularity (a tiny point of space) and has been expanding rapidly ever since.

Question 34

how does CMBR support the big bang theory?

Answer 34

if the theory is true, radiation from the initial explosion should be everywhere but stretched to longer wavelengths by the expansion (which it is - what would have been gamma is now microwave)

Question 35

what are 2 pieces of evidence supporting the big bang theory?

Answer 35

• light from distant galaxies is red-shifted, and the further the galaxy, the more it is red-shifted
• Cosmic microwave background radiation was predicted and then detected

Question 36

what does red-shift mean for the universe?

Answer 36

• most galaxies show a red-shift
• more distant galaxies show a bigger red-shift
• therefore galaxies are moving away; the universe is expanding
• more distant galaxies are moving away faster

Question 37

what is the temperature of CMBR?

Answer 37

~-270 degrees celsius or 2.7 Kelvin

Question 38

what is CMBR?

Answer 38

Cosmic Microwave Background Radiation, the afterglow of the Big Bang - the remains of the thermal energy from the Big Bang, spread thinly across the whole Universe.

Question 39

what was the steady state theory?

Answer 39

proposes that the universe has always existed in a steady state without beginning or end.

Question 40

The Universe is shown to be expanding. How does the big bang vs steady state theory explain this evidence?

Answer 40

• steady state: the Universe is expanding as new matter is being created and pushing the Universe apart.
• big bang: the Universe started with a large explosion that created everything and it is still expanding outward to this day.

Question 41

how was the steady state theory disproved?

Answer 41

High energy radiation would be produced by the big bang. This would not be there in a steady state universe so discovery of cosmic microwave background radiation

Question 42

what are 2 possible endings of the universe?

Answer 42

• big yawn: universe keeps expanding forever
• big crunch: universe stops expanding and collapses

Question 43

what does the future of the universe depend on?

Answer 43

• The future depends on the density of the Universe
• Astronomers think that much of the mass of the Universe is made of some unknown (and currently undetected) material called dark matter.
• If there is enough dark matter the universe will end in a crunch. If there is not enough it will end in a yawn.