Astrophysics - GCSE Flashcards
what is our solar system part of?
It is part of a huge galaxy
how many galaxies are there?
billions upon billions
what is the universe a large collection of?
billions of galaxies
what is the definition of a galaxy?
a large collections of stars
what galaxy are we part of?
the milky way galaxy
what is the distance between the neighbouring stars (stars close to one another) in the galaxy?
it is millions of times greater than the distance between planets in our solar system
what is the name of the force that keeps the stars together in a galaxy?
gravity
what is the movement that galaxies do?
they rotate
how apart are galaxies from each other?
millions of times further apart than the stars within a galaxy
how is the space inside the universe?
it is mostly empty and really, really, really big
how many stars does our solar system contain? and what is its name
one, and it is called the sun
how many planets does the solar system contain and what are they?
it contains 8:
- mercury
- venus
- earth
- mars
- jupiter
- saturn
- uranus
- neptune
how would you describe our solar system?
stuff that orbits around the sun
what are the things you can find inside our solar system?
hint: there are 6 things
- planets
- dwarf planets
- moons
- artificial satellites
- asteroids
- comets
what are planets?
they are large objects that orbit a star
what are dwarf planets?
they are planet-like objects that aren’t big enough to be planets
give an example of a dwarf planet?
lembra de JESSIE
pluto
what are moons?
they are what orbit planets with almost circular orbits. They are a type of natural satellite
what are artificial satellites?
what usually orbit the earth in fairly circular orbits and are man made
what are asteroids? and where are they usually found
- lumps of rock and metal that orbit the sun
- usually found in the asteroid belt
what are comets? how are their orbit? and where do they travel?
- lumps of ice and dust that orbit the sun
- their orbits are usually highly elliptical (a very stretched out circle)
- some travel from near the sun to the outskirts of our solar system
how is the structure of the solar system determined?
it is determined by orbits
what is the definition of orbits?
paths that objects take as they move around each other in space
what does gravity provide?
it provides the force that creates orbits
how do planets move around the sun?
it almost circular orbits
what is happening when an object is travelling in a circle?
hint: 3 points to be made
- it is constantly changing directions
- it is constantly accelerating
- the is always a force acting on it
what is the name of a force that acts when an object is travelling in a circle? and how is it acting?
it is called centripetal force and it acts toward the centre of the circle
what is instantaneous velocity?
the thing which is at a right angle to the acceleration
what keeps the object travelling in a circle?
the instantaneous velocity
what is the force that makes all planets and comets stay in their orbit?
the gravitational force (gravity) of the sun
what does the force due to gravity depend on?
it depends on mass and distance
what is the definition of weight?
the force on an object due to gravity
the variation of weight of any object depends on what?
it depends on the strength (g) of the gravitational field that is in it
what does the gravitational field strength depend on (vary with)?
(hint: there are 2 points to be made)
- it depends on the mass of the body creating the field (the larger the mass of the body the stronger its gravitational field)
- it varies with distance (the closer you get to a planet the stronger the gravitational force is)
give an example of gravitational field strength depending on mass
the earth is more massive than the moon, so an object would weight more on earth than it would on the moon.
if the force is stronger, what else is needed to increases so that it can be balanced?
the instantaneous velocity
the closer you get to a star or planet what will you need to do to remain in the orbit?
you will need to move faster
if the speed of an object in a stable orbit changes, what else will need to change?
the size (radius) of its orbit
how will faster moving objects move in a stable orbit?
it will move with a smaller radius than slower moving ones
what does having different planets orbiting the sun at different speed means?
it means that the distance between planets vary over time
what is the orbit of moons and planets usually like?
it usually is slightly elliptical
what does the word elliptical mean?
elongated
how do comets orbit the sun?
their orbit is very elliptical and orbits with the sun at one focus
what has a longer orbital period than the earth?
comets
why do comets have a longer orbital period than the earth?
they have a longer orbital period because they travel from the outer edges of our solar system, meaning it is more far from the sun then earth is
what happens to a comet when it is near the sun?
it travels much faster when it is near the sun
why do comets travel faster when it is nearer the sun?
it travels faster because the increased pull of gravity makes it speed up the closer it gets to the sun
how long is some artificial earth satellites orbital period.
one day = 24 hours
what are earth satellites called?
geostationary satellites
why are geostationary satellites useful?
it is useful in communication because they are always over the same part of the planet
how do you calculate speed?
speed = distance / time
how do you calculate the distance of a circular orbit?
distance travelled is the circumference of the orbit
distance = 2 x Pi x radius of orbit
how do you calculate the orbital speed?
orbital speed = 2 x Pi x orbital radius / time period
how do you calculate radius?
it is always half the length of the diameter. This means that if the diameter is 4 you need to divide 4/2 which gives you 2
what do stars go through during their life?
they go through some dramatic transformations
what is the first step of a star transformation?
1) stars initially form from a cloud of dust and gas called NEBULA
what is the second step of a star transformation?
2) forces of gravity pulls the dust and gas together to for a PROTOSTAR. Temperature rises as star gets denser and more particles collide with each other. A star is born (not the movie hehehe)
what is the third step of a star transformation?
3) star enters a looong stable period. The energy produced by nuclear fusion tries to expand the star, it balances the force of gravity pulling everything inwards. This stable period the star is called MAIN SEQUENCE STAR and it typically lasts several billion years. The larger the mass of the star, the shorter it’s time on the main sequence.
what is the fourth step of a star transformation?
4) The star is compressed until it is dense and hot enough that the energy (and pressure) created makes the outer layers of the star expand. The star becomes RED GIANT (if it is a small star) or a RED SUPERGIANT (if it is a larger star) It becomes red because the surface cools
what is the fifth step of a star transformation?
5) RED GIANT then becomes unstable and ejects its outer layer of dust and gas. This leaves behind a hot, dense solid core - a WHITE DWARF
what is the sixth step of a star transformation?
6) RED SUPERGIANT starts to glow brightly again as they undergo more fusion to make heavier elements . They expand and contract several times, as the balance the shifts between gravity and thermal expansion. Eventually they explode in a SUPERNOVA
what is the seventh step of a star transformation?
7) the exploding SUPERNOVA throws the outer layers of dust and gas into space, leaving a very dense core called a NEUTRON STAR. If the star is massive enough, it will collapse and become a BLACK HOLE
what is a black hole?
a super dense region of space that not even light can escape from
what is the simple (non-boring) description of a star’s life cycle?
nebula -> protostar -> main sequence-> red giant -> white dwarf
or
nebula -> protostar -> main sequence-> red supergiant -> supernova -> neutron star
or
nebula -> protostar -> main sequence-> red supergiant -> supernova -> black hole
what is a way to classify stars?
by their colours
what does the colour of a star depend on?
on the visible light it emits
how much light each star emits depends on what?
on the star’s surface temperature
what are the colours used to classify stars?
hint: there are 5 colours
- blue
- white
- yellow
- orange
- red
what is the list of hottest to coolest stars?
1) blue
2) white
3) yellow
4) orange
5) red
