p8 Flashcards
why is a star stable while in its main sequence of the its life cycle? (2)
- gravitational force inwards and forces as a result of fusion reaction outwards
- are balanced
what is red-shift?
the observed increase in the wavelength of light from distant galaxies as galaxies move away from us
explain why the velocity of a satellite changes as it orbits the earth (3)
- force of gravity causes the satellite to accelerate towards earth
- the acceleration causes a change in direction of motion
- velocity changes because direction changes
what makes data accurate?
predicted data is very close to the actual data
what leads to a neutron star forming?
a supernova
describe the life cycle of starts much more massive than the sun, including the formation of new elements (6)
- fusion produces new elements
- clouds of dust and hydrogen gas pulled together by gravity is a nebula
- causes increasing temperature to start the fusion process
- to become a protostar
- hydrogen nuclei fuse to form helium nuclei
- and star becomes main sequence
- hydrogen begins to run out (red giant - collapses, outer layers swell out, cool down and turn red)
- helium nuclei fuse to make heavier make heavier elements up to iron
- star expands to become red super giant
- star collapses rapidly and explodes called a supernova
- creating elements heavier than iron
- and distributing them throughout universe
- leaving behind neutron star or black hole
what property of a star does the range of wavelength of radiation emitted depend on?
temperature
describe what happens to a star around the same size aad the sun between the main sequence and the end of the stars life cycle (3)
- star will expand to become a red giant
- star will collapse to become a white dwarf
- stat will cool to become a black dwarf
compare the formation and life cycles of stars with similar mass to the sun and stars with much greater mass than the sun (6)
all stars
- form in a cloud of gas and dust (nebula) by gravity - mostly hydrogen
- form protostar
- fusion begins
- fusion of hydrogen nuclei into helium nuclei
- main sequence star - stable period where gravitational forces inwards balance forces outwards due to fusion processes
differences
- sun sized stars expand to become red giant, bigger stars, expand to become red super giant
- sun sized stars contract and temperature increases to become white dwarf whereas other stars explode in supernova
- sun sized stars cool to become black dwarf, bigger stars become neutron star or black hole
what is a scientific model?
an idea used to explain observations and data
why might scientists have different models?
different models may be appropriate in different situations
why would scientists replace an old scientific model with a new one?
- new evidence
- evidence can not be explained using existing model
- new model explains new evidence
what is the evidence for big bang theory
furthest galaxies are moving fastest. suggests the universe is expanding from a very small region at an ever greater rate
why is peer review an important provess
detects false claims and bias
why would scientists publish unexplained results?
to allow peer review of data
to promote further enquiry
