Chapter 7 Flashcards
Why does our weight change depending on what planet we are on?
The weight of an object is the force acting on it due to gravity. Your mass doesn’t change however on different planets our weight changes eg- mars has less gravity than earth so you would weigh much lighter there.
What does our solar system consist of?
A sun (our star) eight planets and their natural satellites (such as our moon), dwarf planets, asteroids and comets.
Recall the name and order of planets in terms of distance from sun.
My Very Educated Mother Just Served Us Noodles
Start from closest to the sun- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
How have our ideas about the structure of the solar system changed over time?
We use to believe the geocentric model but now believe the heliocentric one
What is Geocentric and Heliocentric?
Geocentric is an earth centered model and Heliocentric is Sun centered model
Describe the orbits of moons, planets, comets and artificial satellites
Moons- rounder
Comets- elliptical orbit
When something has a circular orbit, how does the force of gravity lead to changing velocity of a planet without changing speed?
Objects orbiting the earth, those closer to the earths surface would travel faster because the gravity is stronger so it needs to travel fast enough to avoid hitting the earths surface
What is an orbital period
Time it takes for an astronomical object to complete one orbit around another. The orbital period of a planet depends upon its distance from the sun. The further away an object is from the sun, the longer its orbital period because there is a weaker gravitational force of attraction between it and the Sun.
What is an object doing when its orbitting
Constantly falling but never hitting the ground
Compare the steady state and big bang theories
The steady state theory suggests that as the universe expands new matter is created, so the overall appearance of the universe never changes-Fred Hoyle.
The big bang however suggests that 13.7 billion years ago the universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly into a hot explosion, the universe is still expanding today.
What evidence is there to support the big bang theory
Red shift- If a source of light is moving away from us, the wavelength will appear to increase. The light will appear redder and cosmic microwave background radiation (cmb)-remains of energy created just after the Big Bang
Which theory is there more evidence for?
there is more evidence supporting the Big Bang
theory than the Steady State theory, it is the currently
accepted model for the origin of the Universe
What is the Doppler effect?
If a source of waves is moving relative to an observer, the observed wavelength and frequency will change.
Give an example of train for the Doppler effect and further explain the scenario
As a train moves towards the observer, the waves are pushed together reducing their wavelengths. That means that the frequency increases and the sound will get higher pitch.
Describe the red-shift in light received from galaxies at different distances away form the earth.
How does this provide evidence for the universe expanding
The further from us a star is, the more its light is red-shifted. This tells us that distant galaxies are moving away from us, and that the further away a galaxy is, the faster it’s moving away. THEREFORE IS EVIDENCE THE UNIVERSE IS EXPANDING
How do both the big bang and steady state theory account for red-shift of galaxies.
X
Explain how the discovery of the CMB radiation led to the Big
Bang theory becoming the currently accepted model
Cosmic microwave background radiation is evidence for the big bang theory only. This discovery has led to there being more evidence for this theory and therefore being the currently accepted model.
The evolution of stars is similar to what? Explain the steps
The evolution of stars is of similar mass to the sun through the following stages- Nebula Star (main sequence) Red giant White dwarf
Why is a star stable in its main ‘star’ sequence in its life
The forces are balanced, The outward pressure from the expanding hot gases is balanced by the force of the star’s gravity
How does the balance between thermal expansion and gravity affect the life cycle of a star
It keeps it stable in its main phase for longer, therefore prolongs its life??
The evolution of stars have a…
????
a mass larger than
the Sun
What is blue shift
?
The opposite of red shift- any decrease in wavelength corresponds to an increase in frequency.
Waves moving towards us
How have methods of observing the universe changed over time?
Galileo invented the telescope and allowed him to see into space, however not as well as we can today. In the late 50’s we sent our first satellite into space which allowed us to see more. Our current technology has allowed us to see into the most detail we have ever seen before, through telescopes such as the Hubble telescope.
Why are some telescopes located outside the earths atmosphere?
You must build telescopes at high altitudes, in the earth there will be light pollution (Must be built away from heavily populated areas)
The atmosphere distorts images.
What does the atmosphere do to radiation?
Radiation gets absorbed by our atmosphere- if they didn’t then risks of skin cancer would increase.
Why must gamma ray telescopes be placed in earth orbit? (outside of atmosphere)
The gamma rays cant pass through our thick atmosphere as it absorbs gamma rays.
What does the atmosphere not absorb
radio waves or visible light
Why are radio telescopes situated on the ground?
Radio waves will pass through atmosphere so to save money we keep them on earth
What type of objects/events give out gamma ray bursts
events such as supernovas and black holes give out gamma ray bursts
What are gamma ray bursts
Extremely energetic explosions that are observed in distant galaxies
What are supernovas
The explosion of a star that has reached the end of its life
What started nuclear fusion in space
After Big Bang universe was full of hydrogen atoms, differences of density in clouds of hydrogen caused them to clump together. As gas fell inwards to centre of mass of the clouds, they lost gravitational potential energy which got transferred to kinetic energy of hydrogen atoms causing gas to heat up. Electrons stripped away due to heat causing them to turn to positive hydrogen atoms. Clouds become more dense so hydrogen ions were pushed closer together overcoming the electrostatic force of repulsion and fusion began
Describe 3 stages of nuclear fusion in stars
1- 2 hydrogen nuclei are fused together to form a nucleus of deuterium (single neutron and single proton band together + release of energy)
2-another ionising hydrogen atom, a proton fuses with deuterium a light isotope of helium, helium-3
3- 2 helium-3 nuclei are fused together to form normal helium-4 + 2 protons
Describe overall fusion process for stars
6 ionised hydrogen atoms fuse with 6 protons to form 1 helium-4 atom and 2 protons + energy
Describe process leading up to a red giant
Star runs out of hydrogen to fuse into helium in its core and begins fusing hydrogen in the outer layers- causes it to swell and cool because fusion reaction is spread over wider area
What happens as hydrogen fuel of star begins to run out
The star fuses helium in the core into heavier elements such as carbon
What happens after red giant, if the size of star is less than 1.4x mass of our sun
Outer layers cool and drift away from the core, forming a planetary nebulae leaving a white hot core behind- white dwarf
Describe factors of white dwarf
Doesn’t do fusion
Very dense
Eventually cools leaving behind a non radiating black dark
Shines because of residual heat
What happens after red giant, if the size of star is more than 1.4x mass of our sun
Fusion in outer shells creates heavier elements till energy is insufficient to keep star together against inward pull of gravity and star collapses.
Loss of gravitational potential energy provides energy for nuclear reactions that form heavy elements .
These reactions form a huge number of nutrinos which blow star apart - supernova
If initial star is very light then what will form
A supernova will result in formation of a neutron star
If initial mass of star is large what will form
Gravitational field of star is strong enough to overcome other forces & compresses star down into a black hole
Describe comets orbit
Elliptical orbit that speeds up as they approach the sun and slow down as they move away
What do other rotations include (not orbiting around other objects)
Time taken for planets to orbit about their axis
Eg - time taken for earth to orbit once around its axis = sidereal day- 23 hours 56 mins and 4.1 seconds - length is getting longer as earth rotation slows
What’s a solar day
Time taken for sun to appear in same place in sky everyday
Difference between meteor and comet
Meteor- made of rock
Comet- made of ice and dust
