Space Physics Flashcards
State the life cycle of stars about the same size as the Sun
Nebula → Protostar → Main Sequence Star → Red Giant → White Dwarf → Black Dwarf
State the life cycle of stars much bigger than the Sun
Nebula → Protostar → Main Sequence Star → Red Super Giant → Supernova → Neutron Star OR Black Hole
Where do stars form from?
A cloud of dust and gas (nebula)
What are nubelas known as, and what is meant by this term?
Stellar nursery = where stars are born
How is a protostar formed?
Force of gravity pulls dust and gas together to form protostar (+ temperature increases until hydrogen can fuse)
How is a main sequence star formed from a protostar?
- Star gets denser = temperature rises + more particles collide
- When temp. high enough = hydrogen nuclei undergo nuclear fusion to form helium nuclei (in core)
- Gives out huge amounts of energy = keeps core of star hot → star born
What is meant by a main sequence star entering a long stable period?
Outward pressure (caused by nuclear fusion) trying to expand star balances force of gravity pulling everything inwards
How does a main sequence star become a red giant or red super giant?
- Eventually, hydrogen runs out = begins to fuse with heavier elements
- ∴ Star swells into red giant or red super giant
Name 3 things that occur in red giants/red super giants
- Fusion of helium occurs
- Heavier elements up to iron are created in core of star
- (Becomes) red because surface cools
How does a red giant become a white dwarf?
- Red giant becomes unstable (bc run out fuel + can’t fuse) = eject its outer layer of dust and gas
- Leaves behind hot, dense, solid core → white dwarf
- Glows white hot = extremely hot
How does a white dwarf become a black dwarf?
- White dwarf cools down = emits less energy
- When no longer emits a lot = Black Dwarf
What is a black dwarf a theory?
Haven’t seen a white dwarf cool down = haven’t been enough time from Big Bang
What happens in the core of a star?
- Where temp. + density highest
- Where most nuclear fusion takes place
The more massive a star…
the hotter its core and the heavier the nuclei it can create by fusion
Explain how a red super giant turns into a supernova
- Glow brightly again → undergo more fusion and expand and contact several times
- Form elements as heavy as iron in nuclear reactions
- Eventually, they’ll explode in supernova
- Forming elements heavier than iron and ejecting them into universe to form new plants & stars
Stars & their life cycles produce and distribute …
all naturally occurring elements
Explain how supernova turns into a neutron star
Exploding supernova throw outer layers of dust and gas into space = leaving very dense core → neutron star
When does supernova turns into a black hole
If star is massive enough
What is a black hole?
Super dense point in space that not even light can escape from
What are planets?
Large objects that orbit a star, large enough to have “cleared their neighbourhoods” (i.e. gravity is strong enough to have pulled in any nearby objects apart from their satellites)
What are moons?
- Orbit planets
- Natural satellite
What are dwarf plants?
Planet-like objects = orbit stars but don’t meet rules for being planet
Name 2 qualities of artificial satellites?
- Man-made
- Generally orbit Earth
What are the size of asteroids?
Smaller than planets
What are comets?
Balls of ice and dust that orbit the Sun
What are asteroids?
Rocks in space
What keeps planets and satellites (both natural and artificial) in orbit?
Gravity - provides the centripetal force
If an object is travelling in a circle, what is happening? (direction and acceleration wise)
It’s constantly changing direction & ∴ constantly accelerating
The force of gravity acts …
towards the centre of the orbit
What has to act for an object to accelerate?
Force
What would the force normally cause the object (e.g. planet) to do & why doesn’t this happen?
Fall towards whatever it was orbiting
But object is already moving = causes it to change its direction
If the speed of a satellite changes, what must change?
The radius of the orbit
If speed of a satellite increases, what happens to the radius of the orbit?
It decreases
When the speed of a satellite increases, why does the radius of the orbit decrease?
∵ at higher speed, the satellite needs a greater force of gravity to prevent it from flying off into space
When the speed of a satellite increases, how does decreasing the radius of the orbit help?
By moving closer to the Earth, the gravitational force on the satellite is greater & the satellite remains in a stable orbit
What is the dopper effect?
When a wave source moves relative to an observer = change in the observed wavelength and frequency
What is red-shift?
When wavelengths are longer than they should be - shifted towards the red end of the spectrum
Explain how the universe seems to be expanding
- Light from most distant galaxies = wavelength has increased
- Suggest source of light (distant galaxies) are moving away from us very quickly
- (same result whichever direction you look in)
- Most distant galaxies have greater red-shift than nearer ones
- = more distant galaxies moving away faster than nearer ones
- All galaxies = moving away from every other galaxy
- = whole universe is expanding
What is the big bang theory?
- Initially, all matter in universe occupied a very small space
- Tiny space = very dense & hot
- Then it ‘exploded’ - space started expanding and expansion is still going on
Explain how red-shift supports the big band theory
- Galaxies = moving away from each other at great speed - suggesting something must have got them going
- That ‘something’ was probably a big explosion - the Big Bang
What is Cosmic Microwave Background Radiation (CMBR)?
Form of electromagnetic radiation filling the universe
Where does CMBR come from?
Comes from radiation created from beginning of universe (just after Big Bang)
When was the big bang supposedly?
14 thousand million years ago
