⭐️topic SP7 - Astronomy Flashcards
What is the geocentric model?
The idea that the sun and all the planets are orbiting the Earth; the earth is the Center of everything
Who came up with the geocentric model?
The greeek astronomer ptolemy
What is the heliocentric model?
The idea that the sun is in the centre of the solar system
Who came up with the heliocentric model?
The polish astronomer nicolaus Copernicus
What did the invention of the telescope allow?
Scientists to see objects in space in much more detail and to find new objects
What did Galileo Galilei achieve?
The discovery of four of Jupiter’s moons and by plotting their movements he proved not everything orbited the earth and lead him to support coppernicus’s idea
What other discoveries were made with the improvements of telescopes?
Uranus, Neptune, the dwarf planet Pluto, asteroids and many comets
What is the difference between a comet and an asteroid?
Comets are mostly made of ice, asteroids are rocky bodies
What shape do all the planets move around the sun?
In an elliptical orbit
What are natural satellites?
Moons
What has the invention of photography allowed astronomers to do?
Make detailed observations and measurements.
How have computers affected modern astronomy?
Increased the speed and detail in which info from telescopes can be analysed.
Why are some telescopes in orbit around the earth?
- They give much clearer images as clouds and dust aren’t in the way.
- if the telescope is designed to detect radio waves and infrared emitted by space objects, they must be placed in orbit as the atmosphere absorbs some of that radiation
What is weight?
Mass x gravitational field strength
What is gravitational field strength in earth?
9.81N/kg
What does gravitational field strength on a body depend on?
The mass of the body and the distance from its centre to the surface (radius)
The greater the mass of a body…
…the smaller it’s radius and the greater it’s surface gravity
What are artificial satellites used for?
Communication and to observe earth and space
Describe satellites in highly elliptical orbits
The are used for communication in parts of the earth near the poles
Describe a satellite in a polar orbit
Will eventually pass over all parts of the earth
Describe satellites in circular geostationary orbits
They remain over 1 point on the Earth and are used for broadcasting. They move at 3070 m/s
Describe satellites in low earth orbits
Need the least fuel for launching and they move around 7500 m/s
Why does the force change its direction but not it’s speed on an orbiting body?
As the gravitational force between the earth and the satellite is at right angles to the direction of movement
The gravitational force of a satellite in low orbit is…
…greater than that on a satellite in higher orbit
There are two satellites. A is in a higher orbit than B, which one has to be moving faster to stay in orbit
B as if it slows down, it will fall towards the earth.
What happens when an object falls out of orbit?
It gains speed as it falls until its moving fast enough to stay in a new lower orbit, if it falls into contact with the atmosphere, then the air will slow it down and it’ll eventually fall to earth
How does a star start off?
A nebula - cloud of gas and dust
If the hydrogen in a nebula has a large enough mass?
Gravity will cause it to pull into itself to form a ball being a protostar
How is fusion triggered in starts?
When as the hydrogen atoms accelerate increasing kinetic energy and temperature allowing them to collide due to the increase in pressure
What happens to a protostars once fusion is triggered?
It becomes a main sequence star upon entering the stable phase
What forces are acting on a star?
Outward force of pressure from hot gases and the inward force of gravity causing the stars size to stay almost constant
Why do bigger stars use up hydrogen faster?
As the pressure will be more immense and so the hydrogen atoms are more likely to collide causing fusion at a faster rate
What happens after a star has ended its main sequence?
It becomes a red giant, the fuel has ran out and the Center collapses so all the matter begins to drift out
What is left after a red giant?
A shell of gas which then gets pulled into form a white dwarf (still very hot and eventually a black dwarf
What is the lifecycle of a star?
Nebula, protostar, main sequence star, red giant, white dwarf and black dwarf
What is the sequence of a massive star?
Nebula, protostar, massive main sequence star, red super giant, super nova and then black hole or neutron star
What happens after a super red giant collapse in a massive star?
A supernova explosion due to the huge mass when the Center collapse
When does a super nova form a black hole?
If the cloud of gas left is 4x more than our star
When does a supernova become a very dense neutron star?
If the cloud of gas left os 4x less than our star
What is the definition of the Doppler effect?
The apparent change in the frequency or wavelength of a wave due to the relative motion of the source and the observer
What is the difference in the frequency And wavelength of the sound waves from an ambulance siren between when approaching you and when heading away from you?
When approaching you, the frequency is longer and the wavelength is shorter but when moving away from you, the frequency is shorter and the wavelength is longer
What does it mean if the visible spectrum of light from stars is red shifted?
The stars are moving away from us
How do you know if a star is moving away faster or slower?
If moving away faster, then it’s more red shifted
What is redshift?
A measure of how far along the spectrum the pattern of dark lines in the visible light spectrum have moved
What does the spectrum look like if starts are moving towards us?
The pattern of lines moves towards the blue end of the spectrum as the wavelength of light becomes shorter and frequency increases
What does red shift provide evidence for?
The universe expanding and the Big Bang theory
The further away a galaxy us…
The greater it’s redshift and the faster it’s moving away from us
How does red shift provide evidence for the Big Bang theory?
As the furthest galaxies away are moving faster so if time was reversed, galaxies further away would move back faster and closer galaxies would move back slower and would eventually all meet at one point.
What does the Big Bang theory state?
The universe and all matter in it started as a tiny point of concentrated energy around 13.5 billion years ago
What happened as the universe expanded?
Gravity caused matter to lump together and form stars
What does the steady state theory suggest?
The universe has always existed and is expanding. New matter is continuously created within the universe as it expands
Which theory says matter is being created all the time?
Steady state theory
What does CMB stand for?
Cosmic background radiation
What does the Big Bang theory says about radiation?
Huge amounts of it were released at the beginning of the universe.
What is the radiation released by the Big Bang only detectable as now and why?
Microwave radiation as the wavelength of the radiation has increased
How was CMB discovered?
By a radio telescope which detected microwave signals coming from all over the sky
What does CMB provide supporting evidence for?
The Big Bang theory as it can’t be explained by the steady state theory.
Which universe theory is accepted by more scientists today?
The Big Bang theory as it has more evidence
How do some astronomers explain CMB?
Because the universe is still ‘cooling down’
What’s significant about CMB in different directions?
the same amount is emitted in every direction - it’s uniform
How can scientists measure the distance of a galaxy relative to earth?
By measuring the red shift
