This page contains the detailed and easy notes for Edexcel IGCSE Physics Astrophysics for revision and understanding Astrophysics.
Astrophysics
Space
- Solar System
- Star Life Cycle
- Satellites
- Red Shift
SOLAR SYSTEM
Solar system contains:
- a) Sun- It is the star
- b) 8 planets – They orbit around the Sun in their orbits
- c) Dwarf Planets – They orbit around the Sun in their orbits
- d) Comets – balls of ice and dust orbiting in elliptical orders around the sun
- e) Asteroids – They are made up of rock and metal and are smaller than the planets
- f) Meteors – Shooting stars which dust and debris which burns when they enter the Earth.
FORMATION OF A STAR
Cloud of gas, rock and dust
The cloud condensed and pulled to form concentrate Protostar by the gravitational pull.
The particles collide within the cloud and kinetic energy converted to heat energy which resulted in nuclear fusion releasing massive amount of heat
The fusion releasing heat and light turns a proto star into a star.
The star can attract other rocks and dust and form planets.
LIFE CYCLE OF A STAR
Astrophysics
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SATELLITES
A satellites is the object that revolves around the planet.
NATURAL ARTIFICIAL
eg Moon They are required for weather forecasting, . monitoring the environment, . communication and GPS tracking.
Satellites moved in a particular orbit around Earth. The force is the centripetal forces which arise due to force of gravity and is directed at right angles.
In the orbit the satellites speed and kinetic energy do not change as its speed is the same. But velocity changes due to change in direction.
RED SHIFT
DOPPLER EFFECT
When the source is moving away from the observor, the wavelength of the light increases and it is towards the red region of the spectrum and when the source is moving toward the observor, the wavelength of the light decreases and it moves towards the blue region of the spectrum –
The light coming from the stars and from distant galaxies is red shifted
Further the galaxy, greater the red shift.
UNIVERSE IS EXPANDING
BIG BANG THEORY
The Big Bang theory is the main explanation of how the universe began.
Universe was concentrated into one mass which exploded with a bang and is expanding now as well.
Universe always existed. It will last forever. The denisty of the universe will remain constant
EVIDENCE FOR BIG BANG
Red Shift
Cosmic Microwave Background Radiation
CMBR are the remains of the radiation that comes out from the big bang.
Scientists have discovered CMBR coming from distant galaxies which supports the Big Bang.
KEY TERMS
Solar System – Solar system contains Sun, 8 planets, Dwarf Planets, Comets, Asteroids and Meteors.
Protostar – A protostar is a very young star that is still accumulating mass from its main molecular cloud.
Shooting Star – A shooting star is another name for a meteoroid that burns when it crosses the earth’s atmosphere.
Main Sequence Star – A main sequence star is a star that merges hydrogen into its core/nucleus and has a stable balance of the external pressure of central nuclear fusion and the gravitational forces that push inward.
Red Giant – A red giant star is a dying star in the later stages of stellar evolution.
White Dwarf – White dwarf stars mark the evolutionary end point of mass stars from low to intermediate like our Sun.
Black Dwarf – A black dwarf is all that remains after a white dwarf star burns all its heat, but retains its mass.
Red SuperGiants – A red supergiant is a huge giant star that has consumed its core hydrogen reserve. Helium has accumulated in the nucleus and hydrogen is undergoing nuclear fusion in the outer layers.
Super Nova – A supernova is the explosion of a star, the largest explosion that takes place in space.
Neutron Star – Neutron stars are created when giant stars die in supernovae and their nucleus collapses, and protons and electrons fuse together to form neutrons.
Black Hole – A black hole is a region of space-time that shows a gravitational acceleration so strong that nothing, neither particles, not even electromagnetic radiations like light, can escape from it.
Centripetal Force – A centripetal force is a force that causes a body to follow a curved path.
Red Shift – Redshift is a phenomenon in which an object’s electromagnetic radiation increases in wavelength.
Big Bang Theory – The Big Bang theory is the main explanation of how the universe began.
Cosmic Microwave Background Radiation (CMBR) – The cosmic microwave background (CMB) is believed to be a radiation left over from the Big Bang, or the time the universe began.
Dark Matter – Dark matter is a form of matter that is thought to represent about 85% of matter in the universe and about a quarter of its total energy density.
DISCLAIMER
Disclaimer: I have tried by level best to provide the answers and video explanations to the best of my knowledge. All the answers and notes are written by me and if there is any similarity in the content then it is purely coincidental. But this is not an alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.
References:
BBC Bitesize
Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well