revision unit 18 Flashcards
what are comets
frozen rocks that move around the sun they are elliptical in shape, you can only see them when they get near to earth and they would catch on fire generating light
what are meteors
shooting starts or small rocks that burn up once they enter the atmosphere
how does a star form
- all starts are made of a cloud of gas and dust so the particles in the cloud would get closer to each other due to there gravitational force, so the particles start moving faster. the clouds would merge together and become more and more concentrated and a protostar forms which is a star to be
- as the protostar becomes denser the particles would move faster and start colliding more so more heat will be generated, and the gravitational store would change to thermal store heating the star even much more till the point it gets hot enough and the hydrogen nuclei would fuse together forming helium and even more heat and that when a star would form
note: planets that are too small to become a star would become planets orbiting the star
why are the forces in a start balanced
become the inward force of gravity that trying to make the star contract is equal to the outward force of radiation from nuclear fusion trying to make the star expand
what happens when small stars like the sun run out of hydrogen to fuse
the core of the star would collapse on it self and the outer layers swell out then cool down and turn red then become a red giant, at this stage helium and other light elements would fuse to form a heavier elements, after there is no light elements to fuse the star wouldn’t be producing radiation so the gravity of the star would cause the star to collapse on it self as it changes color to white to be called whit dwarf, then it would cool down and the colour would fade giving us a black dwarf
what happens when big stars much bigger than sun run out of hydrogen to fuse
the core of the star would collapse on it self and the outer layers swell out then cool down and turn red then become a red supergiant, then they would collapse in the collapse the natter surrounding that star core would compress the star more and more till the compression would to a cataclysmic explosion called the supernova, after the super nova the star would ether turn to a neutron star or if the star is big enough it would turn to a blackhole
what is the birthplace of all elements
light elements would come from fusion in the star, starts such as the sun would form light nuclei like helium or carbon nuclei and others light elements, when the star like the sun turns into a red giant it would fuse those elements to form heaver, the heaviest element that can form is iron because there isn’t enough energy, but when a giant star collapses then explodes as supernova the enormous force of collapse would force small nuclei to fuse to form bigger nuclei than iron and the explosion scatters it through the entire universe as the supernova contains all the known elements from lightest to heaviest
explain what happens to planets that orbit the sun
- the force of gravity on the plant acts toward the center of the sun, this force is called the resultant force as no other force is acting on it
- the direction of the plant velocity is change by the centripetal force. ( the direction of motion of any planet in circular orbit is at right angles to the direction of the force of gravity acting on it
- a planet at circular orbits experiences acceleration towards the centre of the circle since the result force acts toward the center of the circle
- the speed of a planet in circular orbit doesn’t change.
how can a satellite orbit earth
for a satellite to orbit around earth it needs to move at a particular speed cause if it was too slow it would fall down and if it was too fast it would leave the atmosphere as that applies to the following rule:
for any smaller body to stay in circular orbit around a bigger body it has to move at a particle speed around the bigger body.
the further a satellite is from the earth or a plant
- the less speed it need for it to stay in circular orbit
2. the longer it takes to move around the orbit once
what is needed for a stable orbit
for a stable orbit, the radius must change if the speed changes
what is a red shift
it is the shift to a longer wavelength of light light from the galaxy telling us that it is moving away from us
what is a blue shift
it is the shift to a shorter wavelength of light from the galaxy telling us that it is moving towards us , that it is
the faster the star is moving (relative to you)….
the bigger the shit is
what did Edwin Hubble conclude
he concluded that:
- all the distant plants are moving away from us
- the more distant the planet it the faster it is moving
