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
red supergiants
red giant stars that fuse hydrogen into helium faster
Life cycle of a massive star
Nebula becomes a protostar, becomes a massive main sequence star, becomes a red super giant, becomes a supernova, becomes either a neutron star or black hole
In a life cycle of a massive star, how is a supernova formed?
At the end of the red super giant period the star rapidly collapses and explodes in a supernova - the outer layers of the super giant cast off and expand outwards
In a life cycle of a massive star, how is a supernova formed?
At the end of the red super giant period the star rapidly collapses and explodes in a supernova - the outer layers of the super giant cast off and expand outwards
how is a black hole formed?
what is left the supernova, the gravity pulls remains together to form a black hole
when and how is a neutron star formed?
Formed when the remains of a supernova are not massive enough to form a black hole so gravity pull them together to form a small, very dense star called a neutron star
what is the sun’s ‘fuel’
Hydorgen
Doppler effect
The sound that our ears detect will change in pitch as the object passes
How does pitch of a sound change?
Due to the frequency of the sound waves
- Lower frequencies mean lower pitch
- Higher frequencies mean higher pitch
how long is the wavelength behind versus in front of the source?
The wavelength is longer behind the source (become ‘stretched’) and shorter in front
What does it mean if the pattern of lines move towards the red end of the spectrum
Star is moving away from us and the light waves become longer and the frequency decreases
What does it mean if the pattern of lines move towards the blue end of the spectrum
The star is moving towards us and the light waves become shorter and the frequency increases
What is a greater red shift mean?
The faster the star is moving away from us
bug bang theory
Theory that the whole universe and all matter and it started out as a tiny point of concentrated energy about 13 .5 billion years ago; the universe expanded from this point; I see universe expanded gravity cause matter to come together to form stars
steady state theory
Theory that says that the universe has always existed and is expanding; new matter is continuously created within the universe as expands
What does The Big Bang Theory state happened at the beginning of the universe
That huge amounts of radiation were released at the beginning of the universe
Cosmic microwave background (CMB) radiation
electromagnetic radiation that fills the universe and is the oldest and most distant light that can be seen
What evidence supports the Big Bang theory?
- The red shift in the light from the galaxies
- cosmic microwave background radiation
What evidence supports the state steady theory?
- The red shift in the light from other Galaxy
- NOT the cosmic microwave background radiation
Why does the cosmic microwave background radiation not support the state steady theory?
Because it provides evidence that the universe has changed over time
What does red shift tell us about very distant galaxies?
That galaxies are moving away from the Earth and that the further away they are the faster they’re moving
what causes a nebula to collapse
gravitational force
Explain why the nebula stops collapsing as it becomes a main sequence star
- gravity causes an increase in temperature until it’s hot enough for fusion until there is balance betweengravity and fusion
what will happen to the start if the gravitational forces are larger than thermal expansion
star will shrink
what will happen to the start if the thermal expansion are larger than gravitational forces
expand
