space physics Flashcards
what is a body in a circular orbit doing?
constantly changing direction and velocity therefore accelerating due to gravity
if the radius of the orbit increases what happens to the speed of the satellite?
speed decreases
what is the life cycle of a star determined by?
the size of the star
explain the life cycle of a star the same size as the sun
- a cloud of gas and dust collapses due to gravity and the light nuclei fuse to form a protostar
- this changes into a main sequence star at high temp and pressure
- then expands into a red giant
- collapse to be a white dwarf
- cools to be a black dwarf and releases no energy
explain the life cycle of a stars that are bigger than the sun
- a cloud of gas and dust (nebula) collapses due to gravity and the light nuclei fuse in a protostar
- this changes into a main sequence star at high temp and pressure
- expands into a red super giant
- star explodes (supernova)
- results in a neutron star or a black hole
what only forms in a supernova?
elements heavier than iron as there are highest temperatures to form heavy elements
what do fusion processes from?
naturally occurring elements
what does a supernova do?
distributes elements throughout the universe
where are lighter elements made?
in main sequence stars and red giants
define red shift
the observed increase in wavelength of light from distant galaxies
what is the relationship between distance and speed of galaxies
the further away the galaxy the faster they move
what is the relationship between distance of galaxy and red shift effect
distance to the galaxies is directly proportional to the size of the red shift
what is the big bang theory
universe began from a very small region that was extremely hot and dense
where did the big bang theory come from?
not a guess but best explanation for many observations
how old is the universe?
14 billion years old
what changed in the observations of supernovae from 1998 onwards?
distant galaxies are receding even faster
what is dark energy doing to the universe?
expected that gravity slows down expansion of space but dark energy is speeding it up
what is dark matter/mass
the missing mass from galaxies that make up its mass apart from the stars, its origins are unknown and its not well understood
The Sun is in the group of main sequence stars. These stars are stable.
Explain why a star remains stable.
expansion due to fusion energy is
in equilibrium with gravitational collapse
Explain why the star is stable while it is in the main sequence stage of its life cycle
gravitational force inwards and forces as a result of fusion reactions outwards are in equilibrium / balanced
