SP7- Astronomy Flashcards
(39 cards)
What is the geocentric model
The idea that the sun and all planets orbit the Earth - there is a sphere of fixed stars
It’s a theory by Ptolemy
What’s the heliocentric model
Nicholas Copernicus thought the sun was at the centre of our solar system
What is good about the invention of the telescope to support heliocentric model
We can see new objects - Galilean moons of jupiter , by plotting there movements jt showed not everything orbited earth is Galileo supported Copernicus
What’s our current model of the universe like
8 planets, 5 dwarf planets, thousands of comets and millions of asteroids
These all move in elliptical orbsit around the sun - many of which have natural satellites
Tell me about photography and astronomy
More detailed observations
Computers for analysis
Why are some telescopes placed in space
In order to detect radiation otherwise absorbed by the atomsphere
What is weight
The force of gravity acting on you
What does weight depend on
Gravitational field strength (g)
What’s the gravitational field strength of earth
9.8 N/kg
1kg of mass is 9.81 N
What does the gravitational field strength on the surface of a body surface of a body such as a planet or a moon depend on
Mass of the body and the distance from its centre to its surface (radius)
Greater the mass and smaller it’d radius, greater its surface of gravity
What shape are most bodies orbits in the solar system
Elliptical
Comets are highly elliptical whereas planets can be almost circular
What does the type of orbit an artificial satellite has depend on
What it is used for
For satellites: what are highly elliptical orbits used for
Communication in parts of the earth near the poles
Tell me about a satellite in polar orbit
It will eventually pass over all parts of the world - orbit goes through poles
Tell me about satellites in geostationary circular orbits
They remain over one point on Seth and are used for broadcasting
Tell me about satellites with low earth orbits
Need the least fuel to launch and travel very very fast
Tell me about a satellites speed and velocity
It’s Speed is constant as it travels but it’s direction is changing constantly - an orbiting body has a constantly changing Velocity
Why does gravity change the satellites direction but not speed
A moving object would continue to go in a straight line unless there’s a force acting to make it change speed or direction - the gravitational force between the earth and the satellite is at right angles to the direction of movement so the force changes its direction
Why does a satellite in low orbit have to move much faster to stay in its orbit than a high orbit
If it slows it will fall towards the earth, it will gain speed as it falls and then be fast enough to stay in a new lower orbit where it count encounter the top of the atmosphere and contact with air will make it slow down and fall to earth
What is a nebula
A cloud of dust and gases (mainly hydrogen)
How does a nebula form into a protostar
Materials can be pulled together by their own gravity, as the cloud (nebula) contracts it becomes denser, the hydrogen becomes hotter as it spirals inwards and may start to glow, as more mass is attracted - gravity gets stronger and heats material more - this is a protostar
When does a protostar become a main sequence star
Eventually temperature and pressures in centre of a protostar evoke high enough to force hydrogen nuclei to fuse together and form helium - fusion reactions like this release a lot of energy as electromagnetic radiation, outward pressure from hot gases balance compression from gravity, it’s now in main sequence stage of life awwww
Why does a main sequence star not collapse?! (What is balanced)
Pressures from hot gases and compression due to gravity
When does a red giant form after a main sequence
When they have fused most of their hydrogen into helium, the core core is not hot enough to withstand gravity and it collapses - outer layers expand to form a red giant
