Stellar evolution Flashcards
a star’s colour is related to ?
its surface temperature
what type of stars are classified by their colour
main sequence stars
if a main sequence star is classified as red, then its temperature will be relatively
cool
if a main sequence star is classified as blue, then its temperature will be relatively
hot
what is a nebula
formed from clouds of dust and gas
stars form from
nebulas ( the clouds of gas and dust inside the nebulas)
a protostar is formed when
after a gravitational collapse, before a main sequence star
how is a protostar formed
the force of gravity inside the nebula pulls particles together until a ball of hot gas forms (this is a protostar)
what happens to the star as particles are pulled closer together from gravity
its density increases
what happens when density of protostar increases
there will be more frequent collisions between the particles which causes the temperature to increase,
this increase in temperature leads to energy being released and nuclear fusion to happen
how does a protostar form and when/how is it classified a mains sequence star (full process)
the force of gravity inside the nebula pulls particles together until a ball of hot gas forms (this is a protostar)
as the particles are pulled closer together, the density of the protostar increases,
meaning more frequent collisions between the particles and temperature is increased which leads to nuclear fusion and energy being released
once nuclear fusion happens in the core, the star os classified as a main sequence star.
how long do main sequence stars live for and why
billions of years as they are stable
from a main sequence star, if a low mass star is formed, what would it be called
red giant
how does a red giant form
after several billions of years the hydrogen causing the fusion runs out.
when it runs out, the fusion also stops
the star will begin to fuse bigger elements like Helium, causing the outer part (surface) of the star to expand
as it expands, it turns into a red giant
after a red giant, what star if formed
white dwarf
how is a white dwarf formed
Once the helium ( or bigger elements) run out, the star collapses and becomes a white dwarf
- overtime it will cool down and the energy it emits also decreases
changes of a white dwarf (temp and colour)
becomes whiter as it contracts and also heats up
the smaller the star, the ___ it lives
longer
what type of gas are stars made from
hydrogen
as a star grows old, what happens to its size
it expands
after a main sequence star, a high mass star will finish its sequence in which stages : (3)
- red super giant
- supernova
- neutron star or black hole
key differences between a high and low mass star (2)
- higher mass stars remain on the mains sequence for a shorter time before they become a red supergiant
- lower mass stars fuse helium into heavy elements like carbon but high mass stars fuse helium into even heavier elements like iron.
for a main sequence star, if it is a high mass star, where does it go next
red supergiant
how is a red supergiant formed
- after millions of years, the hydrogen causing the fusion reactions will run out, meaning that the fusion will also stop.
- the star begins to fuse helium which causes the outer part of the star (surface) to expand
- as it expands, its surface cools down and it becomes a red supergiant
after a red supergiant, what is formed
a supernova
how is a supernova formed
once the fusion reactions inside the red supergiant cannot continue, the core of the star will collapse suddenly and cause a giant explosion (the explosion is the supernova)
- at the centre of the explosion, a dense body called a neutron star will form
the outer remnants of the star are ejected into space forming new clouds of dust and gas (nebulas)
the heaviest elements are formed during a ?
supernova, and they’re ejected into space
the nebulae formed from supernovas can form new ?
planetary systems
after a supernova, what can be formed (2)
black hole or neutron star
what is a black hole
an extremely dense point in space that not even light can escape from
how is a black hole formed
because in most massive stars, the neutron star formed at the centre will continue to collapse in on itself under the force of gravity, until it forms a black hole
how is a neutron star formed
at the centre of the explosion (supernova), a dense body called a neutron star will form
what is the luminosity of a star
the total amount of light energy emitted by the star
luminosity is a measure of
the stars brightness or power output
apparent magnitude is
the percieved brightness of a star seen from earth
apparent magnitude depends on (2)
- luminosity of star
- distance star is from earth
for apparent magnitude, the brighter the star, the __ the apparent magnitude
lower
for apparent magnitude, the dimmer the star, the ___ the apparent magnitude
higher
absolute magnitude is
a measure of how bright stars would appear if they were all placed at the same distance from the earth
why is it difficult to directly measure the brightness of stars
because a bright star which is far away from the earth might look the same as a dim star that is close to the earth
draw the components of a HR diagram
