Chapter 16 - Space Flashcards
what is a comet?
a lump of frozen rock that orbits the sun
what are meteors?
rocks that burn up when they enter the earth’s atmosphere
why do you only see comets when they are near the sun?
they heat up so much that they emit light
the shape of the orbit of a comet
elliptical (squashed circle)
how did the sun form?
clouds of dust and gas were pulled together by gravitational attraction
how was the solar system formed?
the heat from the sun drove the gas in the atmosphere away, creating rocky planets close to the sun and gassy planets farther away
what is a protostar?
a star-to-be
how is a protostar formed?
the clouds of particles are pulled together by forces of attraction so they speed up and collide with more force. This merges the clouds together and a protostar is formed
describe the process by which a protostar turns into a star
a protostar becomes denser, meaning the particles have more energy and speed up, increasing the temperature
if the protostar becomes hot enough, hydrogen nuclei fuse and form helium nuclei
this releases huge amounts of energy which makes the star shine
where is energy transferred from/to in the formation of a star?
gravitational energy store to thermal energy store
what happens to objects formed that are too small to become stars?
they turn into planets orbiting the star
what is a main sequence star?
it is in the middle of the long, stable period which is the main stage in the life of a star
how long does the stable period last?
normally several billion years
what is the heaviest known natural element?
uranium
half life of uranium
4.5 billion years
what makes a star stable?
when the outward force of fusion trying to expand the star and the force of gravity pulling everything inwards are balanced
when does the stable period of a star end?
when most of the hydrogen nuclei have fused to form helium nuclei
why can a comet not be seen when it is far away from the sun?
doesn’t absorb enough energy to burn
one difference between a comet and an asteroid
asteroids are made of rocky material and metals but comets are made of ice, dust and rocky material
one similarity between a comet and an asteroid
both orbit the sun
largest planet in the solar system
jupiter
planet nearest the sun
mercury
why is earth likely to be the only planet where liquid water can exist?
its position in the solar system means it has a temperature between 0 and 100 degrees - the conditions needed for liquid water
why is uranium evidence that the solar system must have formed from a supernova?
they can make other heavier elements by bombarding uranium with neutrons which would have been found in the supernova
what type of star is the sun?
a red giant
what happens to stars when fusion begins to slow down?
it begins to swell out into a red giant or supergiant (depending on size)
the surface turns red as it cools down
why does the surface of a star turn red?
it is cooling down
what happens when a star turns into a red giant?
elements such as helium fuse and heavier elements up to iron are formed in the core
what does a red giant eventually turn into?
a white dwarf
how does a red giant become a white dwarf?
It becomes unstable as no more radiation is released
Gravity forces the star to collapse in on itself
This core heats as it collapses, turning from red to white
why is a white dwarf called a white dwarf?
the heating of the core of the star turns it from red to white and the collapse of the outer layers means it is much smaller than before
how does a white dwarf turn into a black dwarf?
they cool down and release less energy
once it stops releasing a significant amount, it turns black
what happens to larger stars after their long stable period ends?
they swell to become a red supergiant
what is the next stage in the lifecycle of a star after being a red supergiant?
a supernova
how does a red supergiant turn into a supernova?
the star collapses as there isn’e enough energy for fusion
the star gets compressed by gravity and the particles
this compression suddenly reverses, causing an explosion (a supernova)
what are the two things a supernova can result in?
a black hole
a neutron star
how is a neutron star formed?
the neutron star is the very dense core of the supernova
what is a black hole?
a super dense point in space that not even light can escape from
how are lighter elements formed?
from nuclear fusion in the sun and stars
why can elements larger than iron not be formed by fusion?
too much energy is needed
how old is the sun?
5 billion years
what will happen in 5 billion years?
the sun will turn into a re giant, then a white dwarf, then a black dwarf as it stops emitting energy
how are elements heavier than iron formed?
a supernova explosion
why has all the uranium on earth not decayed by now?
very long half life
how are new stars and planets formed by a supernova?
forces such as gravity pull all the debris together and ensures it has every element
what is produced when a supernova explodes?
every known element
how are elements heavier than iron produced and distributed?
the force of a red supergiant collapsing is great enough to force two smaller nuclei to fuse into a bigger one and the explosion of a supernova distributes them all over the universe
what is the orbit of the earth like?
almost circular
what is the force on an orbiting object?
the gravitational attraction between it and the larger body
what is a galaxy?
a huge collection of stars that stay together because of gravity
how long does it take to travel one light year?
one year
how many stars are in the milky way?
100 billion
which colour has the longest wavelength?
red
what increases as the speed of a star or galaxy increases
the red shift
what did Edward Hubble discover?(2)
the light from distant galaxies was red-shifted
the further away a galaxy is from earth, the greater the shift
what is happening to distant galaxies
they are moving away from earth faster than those nearest
what happens to the light rays of something that is moving from you?
the wavelength increases
why is it called the red shift?
as something moves away from you, like the galaxy, the wavelength increases
it is shifted to the red end of the spectrum as this is where the waves are longest
what happens to the light ways of something if it is moving towards you?
they get squashed together and shifts to the blue end of the spectrum where they are most squashed
what is it called when something moves towards you
blue-shift
what is happening to the universe?
it is expanding
the big bang theory of expansion:
everything started in a very small and dense area
the big band explosion started things off and expanded to the universe we know today
although it is much slower, expansion is still happening because of the big bang
what is the steady state theory of expansion?
the galaxies are being pushed apart by matter entering through ‘white holes’
evidence for the big bang theory
scientists have discovered microwaves coming from every direction in space that can only have come from the radiation released during the big bang
what is CMBR
Cosmic Microwave Background radiation
gamma radiation produced just after the big bng
what is dark matter?
the missing mass in galaxies that can’t be seen
what will happen if the density of the universe is less than a specific amount?
it will continue expanding forever and everything will die out
what will happen if the density of the universe is above a specific amount?
it will stop expanding and go into reverse - the Big Crunch
what are the two possibilities for the end of the universe?
the Big Yawn
the Big Crunch
what is the big bang theory?
after the explosion of a supernova from a small, very hot and dense region, the universe is still expanding
what energy is thought to be causing the expansion?
‘dark energy’
what are geostationary orbits?
the object orbits the earth in the same direction as the earth’s spin, so it stays above the same place
when you get closer to a star or planet, what increases?
the gravitational attraction force
as the gravitational force increases, what much happen to the object orbiting the larger body?
its speed must increase
why must the speed of an orbiting object increase as the gravitational attraction increases?
it must speed up to overcome the force of attraction and avoid crashing with the bigger body and to stay in orbit
what happens to the speed of an orbiting object the further from the larger body it is and why?
it slows down
the force of gravity on the object is less so it doesn’t need to travel as fast to stay in orbit
what happens to the size of the orbit the further away a satellite is from earth?
it increases and takes longer to complete one orbit
what direction does the force of gravity from the sun act?
it acts from the centre of the sun to the planet, pulling it towards it
if the speed of an object in a stable orbit increases, what happens to the radius of its orbit?
it will decrease
what is a centripetal force?
a force acting towards the centre of a circle
what is the velocity of a planet?
its direction of motion
what to remember about the force of gravity on a planet and its direction of motion?
they are at right angles to eachother
why does an orbiting planet always accelerate?
it is constantly changing direction
gravity changes its velocity to pull the planet towards the sun but because the planet is already moving, it just changes its direction rather than making it fall towards the sun
what is the acceleration of a planet?
the change per second in its velocity
what happens if a satellite is released too close to earth’s surface?
atmospheric drag means it gradually loses speed and crashes into earth’s surface
what happens if a satellite is released quickly from earth?
it will fly off into space
what happens when a satellite is released correctly?
it moves a constant height and speed in a circular,stable orbit around the earth
what happens when the speed of a rocket increases to keep it constant?
the increase in speed moves it to a higher orbit, where the increased distance means it moves slower, keeping it constant
