Published by admin on

The Universe
A large collection of billions of galaxies
Large collection of billions of stars
Our sun
A star in the milky way galaxy
Orbit a star
dwarf planet
Small planets
orbit planets
artificial satellite
Orbit earth, built by humans
Lumps of rock and metal, found in asteroid belt, orbit sun
Lumps of ice and dust, highly elliptical orbits around sun
Provides the force that creates orbits
centripetal force
A force that pulls object toward the centre of a circle, caused by gravity
Objects travelling in a circle
Constantly changing direction SO constantly accelerating SO resultant force
instantaneous velocity
Tangent to the orbital circle
Gravitational field strength varies with
Mass (larger mass = larger gfs)
Distance (the closer you are to a star/planet, the stronger its gravitational field)
The stronger the force
The larger the instantaneous velocity is needed to balance it
Comets orbit
Comets orbit
Elliptical and elongated
Long orbital periods
Tail points away from sun
Comets are at their fastest
When they are near the sun, the suns pull is stronger and they have most kinetic energy
Comets are at their slowest
When they are furthest from the sun where they have the most GPE
Orbital speed
2 x pi x orbital radius / time period
geostationary satellites
1 day orbital periods
Orbit at same speed of earth rotating
Satellite dishes point at these satellites
Used for weather, communication, google earth
Stellar evolution
1. Nebula
2. Protostar
3. Main sequence star
4. Red/super red giant
5. White dwarf/supernova
6. Neutron star
A large cloud of dust and gas in space
Gravity pulls dust and gas together to form a protostar. As the temp rises, the particles gain energy and collide. The hydrogen nuclei undergo nuclear fusion to form helium nuclei. A star is born.
main sequence star
Thermal expansion and hydrogen are balanced
Red/Super red giant
Hydrogen in core begins to run out, the star is compresses and then gains energy and expands into a red giant/super red giant
White dwarf
Small stars become unstable, eject outer layers of dust and gas and leave behind core
Big stars expand and contract several times and then explode into a supernova
Neutron star
The exploding supernova throws the layers of dust and gas into space, leaving behind a very dense core.
Classifying stars (colours)
The hotter the star, the more light of higher frequencies it will emit, blue is the hottest, red is the coolest
absoloute magnitude
How bright a star would be if it was a fixed distance from earth.
Classifying stars (brightness)
The lower the absolute magnitude, the brighter the star
Hertzsprung-Russell diagram
Hertzsprung-Russell diagram
A graph of absolute magnitude against temperature
Doppler effect
A change in sound frequency caused by motion of the sound source, motion of the listener, or both.
This is because the wavelengths bunch up
Red shift
Galaxies are moving away from one central point. The universe is expanding. The furthest galaxies are moving fastest
The black lines are shifting towards the red end of spectrum
Big bang
Red shift – Universe is expanding, all matter started in one place?
Cosmic Microwave Background Radiation – Detecting CMBR everywhere we observe, leftover energy from explosion?
Categories: Astrophysics