Physics - Topic 8 Space Physics (The Life Cycle of Stars (4)Eventually the…
Physics - Topic 8 Space Physics
The Life Cycle of Stars
4)Eventually the hydrogen begins to run out. The star swells into a red giant(small star) or a red super giant(large star). It becomes red because the surface cools. Fusion of helium occurs. Heavier elements are created in the core of the star.
5)A small to medium sized star like the Sun then becomes unstable and ejects its outer layer of dust and gas. This leaves behind a hot dense solid core - a white dwarf.
3)The star enters a long stable period where the outward pressure caused by the nuclear fusion that tries to expand the star balances the force of gravity pulling everything inwards. In this table period it's called a main sequence star and lasts several billion years.
6)As a white dwarf cools down, it emits less and less energy. When it no longer emits a significant amount, it is called a black dwarf
2)Gravity pulls the dust and gas together forming a protostar, the temp rises as the star gets denser and more particles collide, When temp gets high enough hydrogen nuclei undergo nuclear fusion giving amount a large amount of energy.
7)Big stars start to glow brightly again as they undergo more fusion and expand and contract times, Eventually explode in a supernova and explode elements forming new planets and stars in the universe.
1)Star initially form from a cloud of dust and gas called a nebula,
8)The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star. If its big enough it forms a black hole.
The Solar System and Orbits
Gravity Provides the Force that Creates Orbit
For an object to accelerate, there must be a force acting on it. This force is directed towards the centre of the circle.
This force would cause the object to just fall towards whatever it was orbiting, but as the object is already moving, it just causes it to change its direction.
Also means it is constantly changing velocity.
The object keeps accelerating towards what it's orbiting but the instantaneous velocity keeps it travelling in a circle.
if an object is travelling in a circle it is constantly changing direction, which means it is constantly accelerating.
The force that makes this happen is provided by the gravitational force between the planet and the sun.
Planets move around the Sun in almost circular orbits.
The Size of the Orbit depends on the Object's Speed
2)The stringer the force, the faster the orbiting object needs to travel to remain in orbit.
3)For an object in a stable orbit, if the speed of the object changes, the size of its orbit must do so too. Faster moving objects will move in a stable orbit with a smaller radius than slower moving ones.
1) The closer you get to a star or planet, the stronger the gravitational force is.
Our solar System has One star - The sun
Dwarf planets - Pluto - don't meet all of the rules for being a planet.
Moons - these orbit planets, type of natural satellite.
Planets - large objects that orbit the star, there are 8 in our solar system, have to be able to have a strong enough gravity to pull things in like natural satellites.
Artificial satellites are satellites that humans have built.
Red- shift and the Big Bang
This evidence suggest the universe started with a Bang
Initially, all the matter in the universe occupied a very small space. This tiny space was very dense and so it was very hot.
Then it 'exploded' - space started expanding and the expansion is still going on.
New Evidence Might Change Our Theories
2)There is still lots we do no know. Observations of supernova from 1998 show that distant galaxies are moving away.
3)Currently scientists think the universe is made up of dark matter and energy which holds the galaxies together.
1)Big Bang theory is our best guess, when scientists find new evidence they have to make a new theory or adapt it.
The Universe Seems to Be Expanding
Red-shift shows us that most galaxies are getting further away from us.
More distant galaxies have greater red-shift than closer ones, so further galaxies are moving away faster.
The Doppler effect is when the source of a wave gets further from or closer to the wave receiver, giving the impression that the wave has a lower or higher frequency.
Using this evidence, scientists have concluded that the universe is expanding.
Red-shift is when the frequency and wavelength of light becomes longer due to the Doppler effect.