Space physics

Space physics

1. Star formation

   • Protostar
     • Gas and dust particles are pulled together by the force of gravity and forms a nebulla. As more and more particles of dust and gas come together, the temperature and pressure increases and when it's hot enough, the core starts to glow and we have a protostar.  
     • Main sequence star
       • The outward force due to fusion reaction and radiation pressure is the same as the inward pressure caused by gravity and so the star is in a stable state
       • Red super giant
         • Mass is above 10 solar masses and when the core runs out of elements to fuse, the core collapses. The temperature rockets high and sets of a chain of nuclear reactions causing a supernova explosion
         • supernova explosion
           • The explosion distributes all elements into the universe and creates by fusion, all elements higher than iron
           • Black dwarf
             • If the core is above 3 solar masses, the star collapses to nothing to a single point in space called a black hole where nothing can escape it 
           • Neutron star
             • As the core collapses and reaches up to 3 solar masses, it turns to a neutron star which is extremely dense
       • Red giant
         • Mass is less than 10 solar masses and when the core runs out of elements to fuse, the core collapses
         • White dwarf
           • The core continues to collapse, getting hotter to form a white dwarf that glows due to the high pressure and temperature
           • Brown dwarf
             • The white dwarf then cools down to form a brown drawf
             • Black dwarf
               • The brown dwarf cools down to form a black dwarf

2. Orbit of planets and satellites

   • Planets
     • Newtons three laws
       • No resultant force
         • An object will remain at rest or move with a constant velocity unless it is acted upon by a resultant force
         • Is a resultant force
           • If an object accelerates, it must have a resultant force on it. If an object changes its velocity, it must have a resultant force in it Velocity is speed in a given direction and we can change the velocity by changing the speed or the direction
           • More than one resultant force
             • If object A exerts a force on object B, then object B will exert an equal and opposite force on object A
   • Satellites
     • Satellites can be natural (moons) or manmade and gravity keeps them moving in a circular motion
     • Geostationary satellites
       • These satellites stay above the Earth at the same position and so orbits the Earth every 24 hours and orbits around the equator
     • Polar satellites
       • These are low orbit satellites and they travel over the poles and monitors the entire Earth and travels at a very fast speed

3. Circular motion

   • Planets have a circular motion and they move at a constant speed but not at a constant velocity as the direction changes and so there must be a resultant force acting on it
   • Centripetal force
     • The centripetal force is not a force but ensures that the object moves in a circular motion.  So when a planet orbits, it accelerates towards the centre due to the centripetal force  We can increase the centripetal force by: Decreasing the radius Increasing the velocity Increasing the mass
     • Speed of an orbit
       • The speed of an orbit needs to be right, too fast and it will go into space and too slow and it will fall to Earth

4. Doppler effect

   • When an object comes closer to us, the wavelength decreases and the frequency increases When an object goes further away from us, the wavelength increases and the frequency decreases

5. Red shift

   • Edwin Hubble
     • In 1929, Hubble began studying light from distant galaxies and he discovered 3 things
     • 3 facts
       • Light from distant galaxies are red shifted because the wavelength appears longer and so the galaxies are moving away from us and the universe is expanding The galaxies are moving away from us and each other in all directions The further away from us a galaxy is, the bigger its red shift and the faster it's moving

6. Big Bang Theory

   • Hubble's work suggested that all galaxies started off from a single point

7. Definitions

   • Solar system
     • Consists of the sun and all of the objects that orbit it
   • Sun
     • The sun is a star and it undergoes nuclear fusion and create or produces their own energy and gives out heat and energy
   • Planets
     • Planets have 3 criterias: They must orbit stars They must be massive enough to be spherical They must dominate their neighbourhood and have no other objects at a similar size
   • Dwarf planets
     • Dwarf planets meet all the criteria for planets except the last one and so they don't dominate their neighbourhood
   • Moons
     • Moons orbit planets and they are natural satellites
   • Comets
     • Comets are ice/rocks that orbit the sun
   • Asteroids
     • Large rocks orbiting the sun
   • Galaxies
     • Group of stars
   • Meteors
     • A rock that is suspended in a planet's atmosphere