Space Flashcards
How are stars initially formed?
When a cloud of dust and gas (a nebula) is pulled together by gravity
What is a nebula?
a cloud of dust and gas
How does a nebula form a protostar?
The force of gravity makes the gas and dust (nebula) spiral together, forming a protostar
How does temperature increase in a protostar?
Gravitational attraction causes the density of the protostar to increase. Particles within collide more frequently-> temperature rises
What happens in the protostar when the temperature gets to a certain level?
Hydrogen nuclei begin to undergo nuclear fusion, forming helium nuclei
- gives out masses of energy, keeping the core of the star hot
- can pull smaller masses of gas and dust to form planets to orbit the star
What is a main sequence star?
The long stable period where the outward force of fusion reactions balances the gravity pulling the star inwards (an equilibrium)
- lasts several billion years
What happens when the hydrogen within the star runs out?
-Fusion of helium and other elements occur
-Heavier elements (UP TO IRON) are created at the core
-Star stops being a main sequence star
What happens to stars about the size of the sun when it runs out of elements to fuse?
Expand into a red giant when the star begins to run out of hydrogen
- only red because the surface cools
What is the lifecycle of a star about the size of the sun?
- becomes a red giant
- becomes a white dwarf
- cools down, becomes a black dwarf
- eventually disappearing from sight
What happens to stars larger than the sun when it runs out of elements to fuse?
Expand into Red Super Giants when starting to run out of hydrogen
- expand + contract several times, forming elements as heavy as iron
What is the lifecycle of a star larger than the sun?
- Becomes a Red Super Giant
- Explodes, becomes a supernova
- NOT BIG ENOUGH: Explodes until becoming a Neutron star
OR - BIG ENOUGH: becomes a Black hole
What is a White Dwarf?
When a Red Giant becomes unstable, ejecting its outer layer of dust and gas, leaving behind a hot dense solid core (white dwarf)
What is a Black Dwarf?
When a White Dwarf cools down, emitting less and less energy until it emits an insignificant amount and disappears from sight (a black dwarf)
What is a Supernova?
When a Red Super Giant runs out of elements to fuse and becomes unstable, exploding into a Supernova
- forming elements heavier than iron and ejecting them into the universe -> form new planets + stars
What is a Neutron Star?
When an smaller exploding Supernova throws the outer layers of dust and gas into space
- leaves behind dense core (neutron star)
What is a Black hole?
When a large enough exploding Supernova throws the outer layers of dust and gas into space
- leaves behind invisible, very dense point (black hole)
What is an orbit?
The path on which one object moves around another
What is the Sun orbited by?
Planets: large objects which orbit a star (we have 8), have to have a strong enough gravity to pulled in any nearby objects apart from their natural satellites
Dwarf planets: e.g Pluto, planet like objects that orbit stars but are too small to be a planet
Satellites: objects that orbit a second, more massive object
- Moons (natural satellite)
- Artificial satellites (man-made)
What is a galaxy?
A massive collection of billions of stars that are all held together by gravity
What is the order of the planets?
the sun
My- Mercury
Very- Venus
Easy- Earth
Method- Mars
Just- Jupiter
Speeds- Saturn
Up- Uranus
Naming- Neptune
(Planets)- pluto
How does gravity affect objects in orbit?
- gravity provides the force to keep planet, moons and satellites in orbit
How can an orbiting object have a changing velocity but not a changing speed?
- if the object is travelling in a circle, its constantly changing direction, so constantly accelerating
- therefore it is constantly changing in velocity, but NOT in speed
What does an object in orbit need to accelerate?
- in circular motion, so it needs a force directed towards the centre of the circle
- in the solar system, it is gravity between a planet and sun or planet and satellites
How does the size of an orbit and the objects speed affect each other?
- closer to a star/planet -> stronger gravitational force, so the object needs to travel faster to remain in orbit
- the speed changes-> radius of orbit has to change too
- faster: radius becomes smaller
- slower: radius becomes larger
What is Red-Shift?
When the source of the light is moving away from the observer, so wavelengths are longer than they should be, shifting to the red end of the spectrum
- light from most distance galaxies, the wavelength has increased
What does Red-Shift suggest about galaxies?
- suggests galaxies are moving away from us
- same result in all directions
- more distant galaxies have greater red-shift than nearer ones, so moving away faster than nearer ones
- Conclusion: the universe is expanding
What is the Big Bang Theory?
- Initially, all matter in the universe occupied a very small space
- the space was very dense -> so very hot
- It ‘exploded’, Space started expanding
- Space is still expanding
What is Dark Matter/Mass?
name given to an unknown substance which holds galaxies together, doesn’t emit EM radiation
What is Dark Energy?
thought to be responsible for accelerated expansion of the universe
What are Dark Matter/Mass and Dark Energy both examples of?
Unexplained observations that scientists don’t yet have an explanation for
What does CMBR stand for?
Cosmic microwave background radiation
What is a comet?
elliptical frozen rocks that orbits the Sun
How is a Nebula formed?
Clouds of dust and gas are pulled together by gravitational attraction which forms a NEBULA
Explain the transition from a NEBULA to A MAIN SEQUENCE STAR?
- The particles speed up, merge together, become more and more concentrated, which becomes a PROTOSTAR (star to be)
- As the protostar becomes denser, the particles speed up, so the temp increases
Energy transfers from the protostar’s GPE store to thermal energy store - If it becomes hot enough, the nuclei of hydrogen atoms fuse, forming helium nuclei
- Nuclear fusion releases energy, so it gets hotter, starts to shine and becomes a star
- When an object is too small to become a star, it gets attracted to a protostar to become a planet orbiting the star
- These MAIN SEQUENCE STARS maintain their energy output for millions of years, until there are no more hydrogen nuclei left to fuse
What is a MAIN SEQUENCE STAR?
Stars the radiate energy due to hydrogen fusion –> this is the main stage in the life of a star
Explain the transition from a MAIN SEQUENCE STAR to a RED GIANT?
MAIN SEQUENCE STARS maintain their energy output for millions of years, until there are no more hydrogen nuclei left to fuse
energy released in the core keeps it hot so fusion continues - radiation flows out from the core in all directions
star is stable because the forces within are stable –> the inward force of gravity and the outward force of radiation from the nuclear fusion
These forces stay balanced until most of the helium nuclei are fused
Uranium is the heaviest known natural element –> its existence is evidence that the Solar System must have formed from remnants of a supernova
After the main sequence stage the progression of a star is dependent on its size:
A) Stars around the same size as the Sun:
swell out, cool down and turn red
they are now RED GIANTS –> helium and other light elements for fuse to form heavier elements
Explain the transition from a RED GIANT to a BLACK DWARF?
RED GIANTS –> helium and other light elements for fuse to form heavier elements
when the light elements run out, no radiation released (as there is no fusion)
so the RED GIANT collapses, heats up, turns from red to yellow to white, and becomes a WHITE DWARF
WHITE DWARF then fades out, cools down, and becomes BLACK DWARF
Explain the transition from a MAIN SEQUENCE STAR to a RED SUPER GIANT?
After the main sequence stage the progression of a star is dependent on its size:
Stars that are much bigger than the Sun:
They swell out to become RED SUPERGIANTS, and then collapse
the matter around the star compresses the core more and more and the conversion suddenly reverses in a cataclysmic explosion
Explain the transition from a RED SUPER GIANT to a NEUTRON STAR?
RED SUPERGIANTS, and then collapse
the matter around the star compresses the core more and more and the conversion suddenly reverses in a cataclysmic explosion called a SUPERNOVA
a SUPERNOVA can outshine an entire galaxy for a few weeks
the SUPERNOVA compresses the core into a NEUTRON STAR
a NEUTRON STAR is an extremely dense object made up of neutrons ONLY
during a supernova, the enormous force that collapses, fuses heavier elements together
Explain the transition from a RED SUPER GIANT to a BLACK HOLE?
RED SUPERGIANTS, and then collapse
the matter around the star compresses the core more and more and the conversion suddenly reverses in a cataclysmic explosion called a SUPERNOVA
a SUPERNOVA can outshine an entire galaxy for a few weeks
If the star is big enough, it will become a black hole instead –> its gravitational force is so strong that nothing can escape from it - not even light or any of the other EM waves
during a supernova, the enormous force that collapses, fuses heavier elements together
Draw the flow chart of a nebula to a black hole?
Nebula-> protostar-> main star sequence-> red supergiant- supernova-> black hole
Draw the flow chart of a nebula to a black dwarf?
nebula-> protostar-> main sequence star-> red giant-> white dwarf-> black dwarf
What is the force on an orbiting body?
The force on an orbiting body is the force of gravitational attraction between it and the larger body
What is a centripetal force?
a centripetal force is a force that acts towards the centre of a circle
What type of force is gravity on a planet?
a centripetal force
What is the direction of velocity to a planet?
the direction of velocity on any planet in a circular orbit is at right angles to the direction of the force of gravity on it
Why is the resultant force on an object towards the centre?
the orbiting body experiences acceleration towards the centre of the circle –> the resultant force on it is towards the centre of the orbit
What happens when a satellite is launched too fast or too slow?
- Too slow, it falls to the surface of the Earth
- Too fast, it flies off into space
Some manmade satellites orbit the Earth in a geostationary orbit, what does this mean?
this satellite orbits the Earth in the same direction that the Earth spins –> they remain above the same place on Earth
What are Monitoring satellites + their uses?
Monitoring satellites are fitted with TV cameras
Uses: weather forecasting and monitoring the environment
These monitoring satellites are in a lower orbit than geostationary satellites - they orbit the Earth around once every two or three hours
Where is the sun in the Milky Way?
The Sun is on the outskirts of the Milky Way galaxy
What is a Galaxy?
an enormous collection of stars that stay together due to the force of gravity between them
What did Edwin Hubble discover?
Edwin Hubble discovered that:
- the light from distant galaxies is red shifted
- the further a galaxy is from the Earth, the bigger the red shift is
What is the Doppler effect?
the change in observed frequency and wavelength of a moving object
What does the Big Bang theory state ?
- the universe is expanding after exploding suddenly from a very small, extremely hot and dense region
- space, time, matter and gamma radiation were created in the Big Bang
What is the Steady State theory?
the galaxies are being pushed apart - caused by matter entering the universe through white holes (opposite to black holes)
What is CMBR?
CMBR = Cosmic Microwave Background Radiation = microwaves coming from every direction in space and can only be explained by the Big Bang Theory
What is Dark matter?
dark matter = missing matter in space that makes the average density of the universe much bigger
What happens if the density of the universe is over a certain amount?
it will expand forever –> the stars and everything will eventually die out
What happens if the density of the universe is under a certain amount?
it will stop expanding and everything will go into reverse
