Topic 7 – Astronomy Flashcards
(30 cards)
Why does your weight vary across planets
- Weight is dependant on gravitational field strength (g) as weight = mass x g
- g of a planet varies depending on size of planet
- This means weight will also vary
What does our solar system consist of
- Sun (our star)
- Eight planets
- Natural satellites (such as moon)
- Dwarf planets
- Asteroids
- Comets
List the eight planets in terms of distance from Sun
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
What did Ptolemy suggest about structure of solar system
Earth was at centre of universe (Geocentric)
What did Copernicus suggest about solar system
Sun is at centre and planets orbit it (Heliocentric)
What did Galileo contribute to theories about universe
Used telescopes to support Copernicus’ suggestions about sun and suggested moons orbit planets
Describe the orbits of moons, planets, comets and artificial satellites
They orbit in an elliptical shape
How can the force of gravity lead to changing velocity of a planet but unchanged speed in a circilar orbit
- The force can alter its velocity since direction is continually changing
- It can’t cause a change of speed since there is no force component in the direction of motion
Explain why for a stable orbit, the radius must change if orbital speed changes
- At higher speeds, the object requires a greater centripetal force
- For greater centripetal force, gravitational force must increase
- This is achieved by radius of orbit being reduced
Describe the steady state theory
Universe always existed but is expanding and creating matter to counteract loss in density
Describe Big Bang theory
Universe expanded from very small dense point about 14 billion years ago
What evidence supports Big Band theory
- Red shift
- Cosmic microwave background radiation (CMBR)
What evidence supports steady state theory
Red shift
What theory is currently accepted model for origin of universe and has more evidence
Big bang theory
What is red shift
Perceived increase in wavelength of light received from galaxies due to the source of light moving away from the observer
Compare the observed red-shift of two galaxies, one further away from the other
- Further galaxy traveling faster
- Observed red shift is greater further away source of light is
How does red shift provide evidence universe is expanding
Observed shift in light from distant galaxies towards red end of spectrum indicates galaxies are moving away from us
How did discovery of CMBR lead to Big Bang theory becoming currently accepted model
- It is believed that CMBR originates from radiation produced in big bang
- Expansion of universe has stretched radiation resulting in microwave radiation present today
What factor affect life cycle of stars
- Size of star
What is the life cycle of stars with similar mass to the sun
- Protostar
- Nebula
- Main sequence star
- Red giant
- White dwarf
- Black dwarf
What is the life cycle of stars with a mass larger than the Sun
- Protostar
- Nebula
- Main Sequence Star
- Red Super Giant
- Supernova
- Neutron star or black hole
Describe the transition of star from nebula stage to main sequence star
- Nebula increases in size until it is pulled in due to gravity causing GPE to turn into KE
- Collisions between particles cause kinetic energy to turn into thermal energy
- Nebula will become dense and hot enough to begin fusion
What occurs in stage when star is main sequence star
- Fusion in star releases energy
- Energy balances out with GPE leaving star
- Star is in equilibrium so will not collaps due to gravity or expand due to radioactive behavior. It is stable
- Thermal expansion balances gravity
