Topic 7 - Astronomy Flashcards
Weight of any object depends on
Gravitational field strength(g)
Gravitational field strength depends on
The mass of the body creating the field
The distance from the body
The stronger the gravitational field strength
the larger the velocity needed to balance it and stay in orbit
Our solar system consists of
The sun
8 planets and their satellites
Dwarf planets
Asteroids and comets
The names of the 8 planets in order from least distance to the sun
Mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
The geocentric model stated
The earth was the centre of the solar system. The sun, moon and planets orbited earth in perfect circles.
The heliocentric model
The sun is the centre. The planets orbited the sun in perfect circles. Moons orbited planets.
The current soalr system model
The sun is the centre. Planets orbit in elliptical orbits ratehr than circles.
Moon orbits
Almost circular orbits
Planet orbits
Orbit a star in an elliptical shape
Comet orbits
Highly elliptical orbits
Artificial satellites are
Human built objects that orbit the earth
Artificial satellite orbits
Fairly circular orbits
For planet and moon orbits, they move at
A constant speed but a changing velocity, so they are constantly accelerating
The force that makes the planet or moon change direction is called
The centripetal force
How does centripetal force work
The planet is constantly trying to move straight rather than in an orbit. The centripetal force is always towards the centre of the orbit, so it causes the planet to keep moving but change direction.
If orbital speed changes then
The radius of the orbit must also change
orbital speed increases or decreases effect
Increases - Orbital radius decreases
Decreases - Orbital radius increases
The two theories for the creation of the universe
The steady state theory
The big bang
Steady stae theory states that
The universe has always been how it is now, and always will.
As the universe expands, new matter is constantly created
The density of the universe stays the same
No beginning or end to the unvierse
The big bang theory
All the matter in the universe was in a very small space
Ver ydense and very hot
It exploded, and the expansion started
A finite age for the universe(13.8bn yrs)
Evidence of the big bang theory
Red-shift
Cosmic microwave background radiation
Why is the big bang the accepted theory
It has more evidence than the steady state theory
Red shift full process
Different elements absorb different frequencies and wavelengths of light
When we look at light from distant galaxies compared to erath, it is lower frequency
Theis means it is shifted to the red side of the spectrum
Red shift proves
That all distant galaxies are moving away from us fast
More distant galaxies have greater red-shifts, so the further away, the faster ther moving
CMB radiation is
Cosmic microwave background radiation. Low frequency EM raqdiation(moslty microwaves) detected form all parts of the Universe.
CMB proves big bang because
There has to have been an original source of the radiation, which is the explosion
Red shift can prove both
Big bang and steady state because they both state the universe is expanding
The stages of a star life-cycle
Nebula
Protostar
main sequence star
Red giant/supergiant
Supernova/white dwarf
Neutron star/black hole
Nebula is
A cloud of dust and gas
Protostar process
The force of gravity pulls nebula together. The temperature rises with density. Nuclear fusion starts to occur, which makes the core hot
Main sequence star process
A long stable period
The gravity and nuclear fusion trying to expand the star balance out
The heavier the shorter it spends as this
Red supergiant process
Stars much bigger than the sun become this.
Hydrogen in core runs out, so the nuclear fusion stops and it gets compressed by gravity
The hydrogen and helium outside go through nuclear fusion, so it get even bigger
It turns red because the surface cools
Red giant process
Stars the size of the sun
Hydrogen in core runs out, so the nuclear fusion stops and it gets compressed by gravity
The hydrogen and helium outside go through nuclear fusion, so it get even bigger
It turns red because the surface cools
White dwarf process
A red giant becomes unstable and ejects its outer layers. Only a hot, dense solid core is left
Supernova process
Red supergiants undergo mroe fusion and get brighter again
Heavier elements are made
The balance constantly shifts betwenn graivty and thermal expansion
Eventually it explodes into a supernova
Neutron star/balck hole process
Supernova throws outer layers of dust and gas into space
Leaves a very dense core called a neutron star.
If the star is massive enough, it will collapse and become a black hole
Balck holes are very dense points in space that absorbs everything around it, including light
Telescopes are used to
Observe the universe
Telescopes use
Refraction and reflection to see distant objects
Optical telescopes
Detect visible light
Ways to increase resolution of optical telescopes
Increase aperture of the objective lens
Higher quality objective lens
Aperture is
The diameter of the objective lens(big lens at end of telescope)
Space telescopes
Telescopes located outside the atmosphere
Space telescopes are in space to
Capture light absorbed by the atmosphere
Avoid light pollution and air pollution
Different telescoeps can see
Different types of EM radiation
Different types of telescopes eg
X-ray telescopes
Radio telescopes
