Topic 7 - Astronomy Flashcards
geocentric model
cosmological model that places the Earth at the centre of the universe with the sun, moon, stars and planets orbiting the earth
heliocentric model
sun is at the centre of the solar system with the planets orbiting it
who thought of the geometric model
Ptolemy
who came up with the heliocentric model
Copernicus
in the current model of the solar system how do the planets move
move in elliptical (squashed circle) orbit around the sun
why are telescopes put into space
to delete different types of electromagnetic waves - some may be placed in orbit bc the atmosphere absorbs some of the radiation they are designed to detect
what electromagnetic waves are deleted by telescopes
radio waves, infrared radiation
weight
the force of gravity acting upon an object
weight equation
weight = mass x gravitational field strength
gravitational field strength of Earth
10N/kg
what are artificial satellites used for
used for communication and to observe the Earth and space
name different types of orbits that artificial satellites to be put intolerably
- high elliptical orbits - used for communication in parts of the Earth near the poles
- circular geostationary orbits - orbits remain over one point on the Earth and are used for broadcasting
- low Earth orbits - need the least fuel for launching satellites
- polar orbit - eventually pass over all parts of the Earth
how does the satellite move in orbit
the gravitational force between the Earth and the satellite are at right angles to the direction of movement so the force changes its direction but not its speed
- when in orbit, the satellite has constant speed however its direction is constantly changing - constantly changing velocity
Why is the gravitational force on a satellite in low orbit greater than on a satellite in a high orbit?
A satellite in a low orbit has to be moving much faster to stay in it’s orbit - if it slows down it will fall towards the Earth - the gravitational attraction between the Earth and satellite has to be strong to keep it in orbit
what happens if a satellite gains speed (gravitational attraction)
- if it gains speed it falls until it’s moving fast enough to stay in a lower orbit (the gravitational attraction between the Earth and the satellite is two weak to keep in orbit)
-> if it goes low enough to encounter the top of the atmosphere, contact with the air will slow it down and it will eventually fall to Earth
nebula
Cloud of dust and gases (mainly hydrogen)
protostar
A young star that is still in the early stage of gathering mass from the surrounding gas and dust cloud (nebula)
-> When a nebula’s cloud contracts and becomes denser, the hydrogen becomes hotter as it spirals inwards and may start to glow. As more mass as attracted the clouds gravitational pull gets stronger and heats the material even more.
how does fusion happen from a protostar?
The temperature and pressure in the centre of the protostar become high enough to force hydrogen nuclear fuse together and form helium
what does the fusion inside a protostar release
Lots of energy is electromagnetic radiation - the outward pressure from the hot gases just balances the compression due to gravity
when is a star in its main sequence
When it is fusing hydrogen into helium in its core
how is the red giant star formed?
When the star is in its main sequence and it has fused most of their hydrogen into helium; the core is not hot enough to withstand gravity and it collapses the outer layers expand to form a red giant star
when is a shell of gas formed
After billions of years, the red giant star throws off a shell of gas
when is a white dwarf star formed
When the rest of the red giant star is pulled together by gravity and collapses to form a white dwarf star
what is the life cycle of a star
Start of a nebular, becomes a protester, becomes a main sequence star, becomes a red giant, becomes a shell of gas, becomes a white dwarf
