space physics Flashcards
mass
the amount of matter an object has
weight
a force exerted by an object
weight
mass x gravity
gravity
The force of attraction between any two objects which have a mass.
What is in the centre of the solar system?
The sun as it has the greatest mass therefore the strongest force of gravity.
Satellite
It is an object that orbits (goes around in a circular motion) around another object. The moon is a natural satellite for the earth, the moon orbits around the earth as the earth is heavier and has a higher gravitational field strength.
Nuclear fusion
-It is the process which power up stars and allows them to release energy. Nuclear fusion is the joining of two small nuclei to produce a large nucleus.
Sun
The sun has a great mass, therefore a strong force of gravity. The sun is in the centre of the solar system as it takes up 99% of the mass of the solar system.
The birth of a star (any size star)
1, Nebula- dust and gas (hydrogen) in the universe are brought together due to gravity and produce the core of the star.
2, Protostar- the core of the star produced during the nebula starts to heat up and this is due to the particles having high kinetic energy
3, Main sequence star- hydrogen gas in the star will fuse together (nuclear fusion) as the core is hot and gravity is proving high pressure for the reaction to occur. Gravity applies a force on the star inwards, and with the fusion reaction force is applied outwards. Our sun is at this process currently and releases energy.
The death of a star (small-like the sun)
1, Red giant- Eventually the hydrogen in the star will run out, this means the star will only contain helium. The helium will now undergo nuclear fusion, but as helium is a heavier element more energy will be released, more outwards force thus the size of the star will increase.
2, White dwarf- Nuclear fusion will continue to occur with heavier elements and the size of the star will constantly increase until we reach iron. Iron is the heaviest element that can undergo nuclear fusion. This will mean there is no longer an outwards force acting on the star (but gravity still acts inwards), causing the star to shrink in size.
3, Black dwarf- starts losing energy- light goes
Death of a star (medium and large)
1, Red supergiant- Eventually the hydrogen in the star will run out, this means the star will only contain helium. The helium will now undergo nuclear fusion, but as helium is a heavier element more energy will be released, more outwards force thus the size of the star will increase. As the star has more mass and is larger in size, the red super giant will be greater in size and lot more energy compared to the red giant.
2, Supernova- As the star has a high outwards force due to nuclear fusion, the star will get warmer and eventually explode with high pressure. Elements heavier than iron are produced.
Medium star- end of life cycle
Neutron star- It is produced as the final product in a medium star. This star consists of neutrons tightly packed together (in the milky way there are over 2000 neutron stars laying around)
Large star- end of life cycle
Black hole- are produced at the end of the life cycle of a large star when the neutron will further compress into a black hole. As the star originally was so big in mass, the black hole has an extremely strong force of gravity. The strength of pull of gravity is so strong that not even light (3 x 10^8 m/s) can escape the pull. 21 billion times bigger than the sun.
Big bang theory
The universe initially started off as all the mass was located in a dense region, and there was a colossal explosion between the mass which created the universe. The universe is ever expanding.
Evidence for the Big Bang theory
1, Cosmic microwave background radiation–> this is the natural radiation which is found in the atmosphere, and it is the remaining radiation from the big bang collison.
2, Red shift- this is the evidence that supports that the universe is ever expanding, this is as the light shifts towards the red end of the spectrum. As red light has a higher wavelength when light shifts towards the red end of the spectrum it suggests that the planets are moving away.
The gravitational field around planets is strong enough to have pulled in all nearby objects with the exception of
natural satellites
The gravitational field around a dwarf planet is
not strong enough to have pulled in nearby objects
What are the 4 rocky planets?
Mercury, Venus, Earth and Mars
What are the 4 gas planets?
Jupiter, Saturn, Uranus, Neptune
What are moons examples of?
natural satellites
Artificial satellites
- man-made and can orbit any object in space
- The International Space Station (ISS) orbits the Earth and is an example of an artificial satellite
A single orbit is called the planet’s
year
What also orbits the sun?
asteroids and comets
What is an asteroid?
A small rocky object which orbits the sun
Where does the asteroid belt lie?
Between mars and Jupiter
Comets
- Comets are made of dust and ice and orbit the Sun in a different orbit to those of planets
- The ice melts when the comet approaches the Sun and forms the comet’s tail
Our solar system is one part of the
milky way galaxy
How many stars are in the Milky Way galaxy?
Billions
Some of the stars in the Milky Way galaxy
have planets which orbit them
The universe is made up of
many different galaxies
How many galaxies are there estimated to be in the entire universe?
More than 100 billion galaxies
What does a planet orbit?
The sun
What does a moon orbit?
A planet
What does a comet orbit?
Sun
What does an asteroid orbit?
Sun
What does an artificial satellite orbit?
An object or body in the solar system
What determines what will orbit another body?
The size- A smaller body or object will orbit a larger body
What does there have to be in order to orbit a body?
- there has to be a force pulling things towards that body
- Gravity provides this force
The gravitational force exerted by the larger body on the orbiting object
-is always attractive
Gravitational force
- Therefore, the gravitational force always acts towards the centre of the larger body
- The gravitational force is the centripetal force as it will cause the body to move and maintain in a circular path
Circular motion in an orbit
- Planets travel around the Sun in orbits that are (approximately) circular
- Objects in circular orbit are travelling at a constant speed
- The orbit is a circular path, therefore the direction in which the object is travelling will be constantly changing direction
- A change in direction causes a change in velocity
- Acceleration is the rate of change of velocity, therefore if the object is constantly changing direction then its velocity is constantly changing and so the object in orbit is accelerating
- A resultant force is needed to cause an acceleration
- This resultant force is gravity and it must act at right angles to the instantaneous velocity of the object to create a circular orbit
- This is always towards the centre of the orbit
- The instantaneous velocity of the object is the velocity at a given time
There are several similarities in the way different planets orbit the Sun
- Their orbits are all slightly elliptical (stretched circles) with the Sun at one focus (approximately the centre of the orbit)
- They all orbit in the same plane
- They all travel the same direction around the Sun
There are also a few differences:
- They orbit at different distances from the Sun
- They orbit at different speeds
- They all take different amounts of time to orbit the Sun
asteroids are
pieces of rock which orbit the sun
Moons
- They are natural satellites which orbit planets
- Moons will orbit planets in a circular path
- Some planets will have more than one moon
- The closer the moon is to the planet:
- The shorter the time it will take to orbit
- The greater the speed in the orbit
Artificial satellites
- A satellite needs to travel at a specific speed to maintain a circular orbit at a particular distance from the object
- If the speed of the satellite is too big:
- The radius of the orbit will increase and the satellite will spiral into space
- This is because the gravitational attraction cannot provide enough force to keep it in orbit
- If the speed of the satellite is too small:
- The radius of the orbit will decrease and the satellite will move towards the object it should be orbiting
- This is because the gravitational attraction is too strong to maintain a constant orbital radius
- If an artificial satellite is to change the radius at which it is orbiting then the speed at which it is travelling must change
- To maintain a stable orbit:
- If the speed increases the radius must increase
- If the speed decreases the radius must decrease
galaxy
constellation of stars
Gravity
The force of attraction between any two objects that have a mass
Dwarf planets are
extremely small
The solar system also includes (apart from planets)
moons, asteroids and comets
How many moons do most of the planets in the solar system have?
At least one
What is the solar system a part of?
The Milky Way galaxy
What is a galaxy?
It is a massive group of stars
How many stars does the Milky Way contain?
Hundreds of billions
How many galaxies does the Universe contain?
Hundreds of billions
What is a nebula?
A cloud of dust and gas
What is the main gas in a nebula?
Hydrogen
What is a protostar?
A collapsing cloud of hot dust and gas
What does the force of gravity tend to do to a star?
It tends to make it collapse
What force does the energy from nuclear fusion tend to do?
It tends to make the star expand
The main sequence star is in
equilibrium
When are elements heavier than iron produced?
In a supernova
In what paths do planets orbit the sun?
In eliptical paths
What do comets orbit?
The sun
What do moons orbit?
Planets
How does the gravitational force vary close to the sun?
It increases
What are asteroids?
They are pieces of rock that orbit the sun
What is a galaxy?
It is a consellation of stars
Features of eliptical orbits
- speed is constant
- velocity changes at every point on the path
- accelerate
- centripetal
When is a star in equilibrium?
When the inward pull of gravity and the outward pressure acting on the star are equal.
If the temperature drops, what will happen to the outward pressure?
It will decrease, causing the star to contract.
Where are elements heavier than iron produced?
in a supernovae explosion
A smaller orbit/body will
orbit a larger body
The gravitational force exerted by the larger body on the orbitting object is
always attractive
What is the gravitational force?
It is the centripetal force as it will cause the body to move and maintain a circular path.
What are several similarities in the way different planets orbit the sun?
- their orbits are all slightly elliptical (stretched circles) with the Sun at one focus (approximately the centre of the orbit)
- they all orbit in the same plane
- they all travel the same direction around the sun
What are a few differences in the way planets orbit the sun?
- they orbit at different distances from the sun
- they orbit at different speeds
- they all take different amounts of time to orbit the sun
Planets furthest from the sun take
the longest amount of time to orbit the sun- they travel at the slowest speeds
How long to planets closest to the sun take to orbit the sun?
the shortest amount of time to orbit the sun- they travel at the fastest speeds
In what path do moons orbit planets?
circular paths
The closer the moon is to the planet:
- the shorter the time it will take to orbit
- the greater the speed in the orbit
Why does a satellite need to travel at a specific speed?
To maintain a circular orbit at a particular distance from the object
What happens if the speed of the satellite is too big?
The radius of the orbit will increase and the satellite will spiral into space because the gravitational attraction cannot provide enough force to keep it in orbit
What happens if the speed of the satellite is too small?
The radius of the orbit will decrease and the satellite will move towards the object it should be orbitting. This is because the gravitational attraction is too strong to maintain a constant orbital radius.
If an artificial satellite is to change the radius at which it is orbitting, what must change?
The speed at which it is travelling
If the speed increases, what must happen to the radius?
it must increase
if the speed decreases what must happen to the radius?
It should decrease
How do comits orbit?
- their orbits ar highly eliptical or hyperbolic
- This causes the speed of the comets to change significantly as the distance from the Sun changes
- Not all comets orbit in the same plane as the planets and some don’t even orbit in the same direction.
How is a stable orbit of a comet achieved?
- as the comet it loses gravitational potential energy and gains kinetic energy
- This causes the comet to speed up
- This increase in speed causes a slingshot effect, and the body will be flung back out into space again, having passed around the Sun
- As it moves away from the Sun the body will slow down, eventually finishing its orbit and falling back into towards the Sun once more
- In this way, a stable orbit is formed
