Space Flashcards
Name the life cycle for a star around the same size as our sun.
- Nebula
- Protostar
- Main sequence star
- Red giant
- White dwarf
- Black dwarf
Name the life cycle for a star much larger than our sun.
- Nebula
- Protostar
- Main sequence star
- Red supergiant
- Supernova
- Neutron star
- (Rarely) Black hole
How is a protostar formed?
Gravitational attraction between clouds of dust and gas (a nebula) cause them to merge and form a protostar
How is a main sequence star formed?
- Protostar becomes denser as gravitational forces pull it together, so MFSC between particles
- So more energy from the gravitational potential energy store is transferred to the thermal, so temperature increases
- When the temperature is high enough, hydrogen nuclei fuse to form helium nuclei (nuclear fusion)
- These reactions release huge amounts energy -> protostar becomes a main sequence star
Why is a star stable in main sequence?
The outward forces produced by nuclear fusion reactions are in equilibrium to the gravitational forces pulling inward
In objects in circular orbits, what is constantly changing?
Direction -> velocity
In planets and satellites, what provides the resultant force to maintain orbit?
Gravity
Why do satellites have a changing velocity?
- Gravity causes an acceleration towards Earth and a change of direction, so the velocity is changing
For a satellite, does the speed increase or decrease with distance from earth?
Decrease
What provides centripetal (resultant) force for a satellite?
Gravity
State 2 factors that determine the size of the centripetal (resultant) force on a satellite.
- Distance from Earth/celestial body
- Speed
How is a current induced in a wire of a satellite?
- As the wire moves through Earth’s magnetic field
- A p.d. is induced
- Wire must be part of a complete circuit
Explain red shift.
- A moving object creates waves which have a greater wavelength
- Red light has the greatest wavelength so a moving star produces a red light
How can red shift be used to explain the Big Bang Theory?
- As a star is moving away, it has a longer wavelength
- Which is observed as red light or “red shift”
- Light from distant galaxies have more red shift, so this tells us that they are receding/moving out from a point -> the universe is expanding
What does the Big Bang Theory say the universe started from?
A very small, dense and hot region that expanded outward
What are the nuclei of all naturally-occurring elements produced by?
Nuclear fusion in stars
How are helium nuclei formed?
From fusion of hydrogen nuclei
Where are small nuclei formed? (not helium or hydrogen)
In stars with large masses
What happens when a star becomes a red giant or red supergiant?
Helium, lithium and other small nuclei are fused to form larger nuclei
What is one theory about why the universe expands?
Dark matter is responsible for the acceleration of the expansion of the universe
Name 2 beliefs about dark matter.
- Dark matter could be responsible for the acceleration of the expansion of the universe.
- Dark matter could provide the gravitational force that holds galaxies together.
What do scientists believe about the speed of the expansion of the universe?
It is increasing
Which elements are only produced in a supernova?
Elements heavier than iron
To change the speed of an object in stable orbit, what must change?
Radius of orbit/distance from Earth
How does gravity make objects in orbit change velocity but not speed?
- Gravity provides resultant/centripetal force
- Which keeps them
moving in a circle - So they are constantly changing direction
