P16 Space Flashcards
what is at the centre of the solar system?
the sun
what is the sun?
a star
what are the relatively small, rocky planets?
Mercury
Venus
Earth
Mars
what are the larger planets in the solar system?
Jupiter
Saturn
Uranus
Neptune
what are moons?
natural satellites which orbit planets
what is a galaxy?
a massive group of stars
how do stars form?
they form from clouds of dust and gas (a nebula)
in the first stage, gravity causes the nebula to collapse
as the particles move faster, the temperature rises forming a protostar
if the temperature increases enough, it will cause the hydrogen nuclei to undergo nuclear fusion and form helium
this releases a huge amount of energy
what are the forces inside a star?
the force of gravity acts inwards and makes the star collapse
the energy from nuclear fusion acts outwards and makes the star expand
what is a nebula?
a cloud of dust and gas
what is the main sequence of a star?
a stable stage in the life cycle of a star where nuclear fusion occurs
there is a balance between the outwards force of radiation and the inwards force of gravity
what happens to stars that are the same size as the sun?
the hydrogen begins to run out so the outwards force due to fusion becomes smaller
the force of gravity causes the star to collapse inwards which increases the temperature
helium nuclei fuse together to make heavier elements and the star expands to form a red giant
the star then stops fusing helium and shrinks to a white dwarf
the star cools down and stops releasing energy and forms a black dwarf
what happens to stars much bigger than the sun?
when they run out of hydrogen, they expand to form red super giants
helium nuclei fuse together to form heavier elements
fusion then stops and the star explodes in a supernova
which elements are produced in a supernova and why?
elements heavier than iron
as the temperature is high enough
what happens to the elements made in a supernova?
they are distributed across the universe when the supernova explodes
what can be formed from a supernova?
a neutron star
a black hole
what is a neutron star?
neutrons densly packed together
what is a black hole?
a great amount of matter packed into a very small area
the gravity is so large that light cannot escape
what is a circular orbit?
when a satellite’s orbit follows the path of a circle
what is an eliptical orbit?
when planets follow the path of an elipses?
what holds a planet in orbit?
the force of gravity between the sun and the planet
what are geostationary satelites?
satelites which orbit once around the earth every 24 hours so always point at the same point on the earth
why does the force of gravity on a satellite cause a change in velolity but not in speed?
the velocity is speed in a given direction
in a circular orbit, the direction of the satellite is constantly changing so the velocity is constanty changing
the speed is constant
what happens if the speed of a satellite orbiting the earth changes?
the radius of the orbit must change
if the speed increases, the radius decreases
this is because the object needs a greater force of gravity to stop it from flying out to space
what does a decreased radius of a satellite’s orbit cause?
the gravitational force on the satellite is greater and it stays in a stable orbit
what are the properties of light from distant galaxies?
it has a longer wavelength than light from closer galaxies
what are the dark lines on an absorbtion spectrum of light from a star and why do they appear?
they are where elements in the star absorb certain wavelengths of light
what is red-shift?
the change in wavelength of light from distant galaxies to the red end of the spectrum
how does red-shift show that galaxies are moving away?
as they are moving away, the light waves are stretched so their observed wavelengths are increased
if a galaxy has a larger red shift, what does it mean?
the galaxy is further away and moving faster
what is the evidence for the universe expanding?
the fact that distant galaxies are moving faster than nearer galaxies
what is the big bang theory?
that the universe formed from a small region that was hot and dense and expanded into the universe
what is the strange thing that scientists observed around 1998?
the rate of expansion of the universe is increasing which cannot be explained
what is a suggestion for the reason the universe is expanding faster?
there is matter and energy we cannot detect called dark matter and dark energy
what between distant galaxies and earth is expanding?
the space between us
the galaxies aren’t moving away by travelling through space
