Astrophysics Flashcards
A universe is a large collection of what?
Billions of galaxies
A galaxy is a large collection of…
Billions of stars
Why does gravitational field strength vary?
Any object with mass exerts the force of gravity, and the higher the mass (of the body creating the field), the higher the force of gravity exerted.
The larger the planet and the higher its mass, the higher the gravitational field strength and the stronger the gravitational field
e.g., the earth is more massive than the moon, soon object would weigh more on earth than it would on the moon
Why does gravitational force cause moons to orbit planets?
Moons and artificial satellites are attracted to their planets, and so are pulled towards them.
This gravitational force keeps them moving in curved paths called orbits
How does gravitational force cause planets to orbit the Sun?
The Sun’s gravity pulls the planets in orbit around it.
this is because an object that is moving in a circular orbit at a constant speed is constantly accelerating as the velocity is changing . the force causing the acceleration is the centripetal force which acts towards the centre of the circle (without the object already moving on its own, the object would fall towards whatever it is orbiting). In other words, a planet has a velocity, however the force of gravity deflects its motion, keeping it orbiting
What are geostationary orbits?
Due station orbit are satellites that always appear in the same position above the arts surface, which is important the satellite communication
Orbit of comets, moon, planets
Comments have elongated, elliptical, orbits,
planets and moons have circular orbits
Orbital speed relationship
(2 x pi x orbital radius)/time period
What is luminosity?
The amount of energy emitted per second by a star
How are stars classified according to the colour?
The colour of a star is linked to its (surface) temperature; the hottest stars are blue, and the coolest stars are red
Evolution of a star
A star is first born when a cloud of cold, hydrogen gas and dust collapses due to the pole of gravity. As the cloud collapses, the atoms and molecules move very fast. As molecules collide with each other, the store of kinetic energy is transferred to the internal energy store of the gas, and the temperature rises to several million degrees Celsius. The contracting and heating. All of gas is called a protostar.
The temperature in the gas becomes so high, that hydrogen nuclei began to collide and fusion begins
Then the star becomes a main sequence star, which means that it releases energy from the fusion of hydrogen to form helium. The inward forces of gravity which tend to collapse the star, are balanced by the outward forces created by pressure inside the hot core.
Stars about the size of the sun:
When the supply of hydrogen begins to run out, the start becomes unstable. Without the fusion of hydrogen, the pressure inside the star drops, and the outward forces decrease, and the star begins to collapse. As the star collapses, the temperature of the court increases, even farther and helium begins diffuse to make heavier elements such as carbon and oxygen. The hot core causes the start to swell up into a red giant.
When the start is no longer able to fuse helium, and it’s cool, cool down the star collapses into a white dwarf star and the surface of the white dwarf is hot. Fusion stops, and the stars life is over, at this stage, the white dwarf calls down, and it becomes a dark, called star known as a black dwarf.
Stars much larger than the Sun
When the start reaches the end of its main sequence stage, it begins to collapse, but the star grows into a red super giant. The fusion energy and red supergiants is sufficient for heavier elements to be made in the fusion process. Iron is the heaviest metal made inside stars due to fusion. After millions of years as a red super giant, the star runs out of its nuclear fuel and the cool calls down and inwards and forces of gravity overcome the outward pressure from the centre at the star which means that there is a very rapid collapse of the star. then two things can happen, the star can either turn into a supernova or a neutron star.
The rapid collapse could heat the inside of the star to such a high temperature, that the star explodes, and the remnants of a supernova spread out into space, which eventually form another gas cloud which forms new stars. What could also happen is, the great gravitational forces could cause the centre of the star to collapse into a highly condensed form of matter, which would mean that the court could be led as a neutron star made of only a few neutrons it could also become a black hole
Evolution of a star
A star is first born when a cloud of cold, hydrogen gas and dust collapses due to the pole of gravity. As the cloud collapses, the atoms and molecules move very fast. As molecules collide with each other, the store of kinetic energy is transferred to the internal energy store of the gas, and the temperature rises to several million degrees Celsius. The contracting and heating. All of gas is called a protostar.
The temperature in the gas becomes so high, that hydrogen nuclei began to collide and fusion begins
Then the star becomes a main sequence star, which means that it releases energy from the fusion of hydrogen to form helium. The inward forces of gravity which tend to collapse the star, are balanced by the outward forces created by pressure inside the hot core.
Stars about the size of the sun:
When the supply of hydrogen begins to run out, the start becomes unstable. Without the fusion of hydrogen, the pressure inside the star drops, and the outward forces decrease, and the star begins to collapse. As the star collapses, the temperature of the court increases, even farther and helium begins diffuse to make heavier elements such as carbon and oxygen. The hot core causes the start to swell up into a red giant.
When the start is no longer able to fuse helium, and it’s cool, cool down the star collapses into a white dwarf star and the surface of the white dwarf is hot. Fusion stops, and the stars life is over, at this stage, the white dwarf calls down, and it becomes a dark, called star known as a black dwarf.
Stars much larger than the Sun
When the start reaches the end of its main sequence stage, it begins to collapse, but the star grows into a red super giant. The fusion energy and red supergiants is sufficient for heavier elements to be made in the fusion process. Iron is the heaviest metal made inside stars due to fusion. After millions of years as a red super giant, the star runs out of its nuclear fuel and the cool calls down and inwards and forces of gravity overcome the outward pressure from the centre at the star which means that there is a very rapid collapse of the star. then two things can happen, the star can either turn into a supernova or a neutron star.
The rapid collapse could heat the inside of the star to such a high temperature, that the star explodes, and the remnants of a supernova spread out into space, which eventually form another gas cloud which forms new stars. What could also happen is, the great gravitational forces could cause the centre of the star to collapse into a highly condensed form of matter, which would mean that the court could be led as a neutron star made of only a few neutrons it could also become a black hole
Evolution (short version-similar mass to earth)
Protostar/nebula – star (main sequence) – red giant –white dwarf – black dwarf
Absolute magnitude
How bright a star appears to us, depending on the energy the star emits per second, and how far the star is away from us. Absolute magnitude measures how bright the star would appear at an agreed set distance away from us. The agreed distance is 10 parsecs
Apparent magnitude
Apparent magnitude is how bright a star appears to the eye
Evolution of the universe
Up to 0.1 second: The early universe is populated by highly energetic particles and photons (no protons or neutrons yet)
After a few seconds: the universe has cooled sufficiently for, protons, neutrons and electrons to exist
After three minutes- 30 mins : the universe cools, further and nuclear fusion occurs, so that protons fuse to form helium-4 nuclei and DEUTERIUM
For the next 700,000 years: the universe continue to expand and cool down.
Over the next billion years: gravity acted on clouds of expanding gases, and the force of gravity pulls the expanding clause of gases into large clumps, which forms stars and galaxies.
now- new starts continue to expand and evolve.
Cosmic microwave background radiation
When the universe was young, it was very hot and the temperature of the background radiation was around 4000 K. As the universe expanded over billions of years, called and the wavelength of background of radiation increased.
The CMB radiation is a distant echo which confirms a long time ago, the universe was very hot and full of short wavelength radiation produced by the big bang.
The Doppler effect
We have all had an ambulance coming towards us and then passed us. As the ambulance goes past us and moves the way we hear the pitch of sound from the siren become lower (fewer waves per second). The frequency of the sound waves here has decreased and the wavelength has increased.
What is Redshift?
Red shift is when, the source of light moves faster away from us, the wavelength of light we see increases (and frequency decreases compared to the light originally emitted by the source) which produces a greater red shift, which means the light moves towards the red end of the spectrum.
this tells us that if distant galaxies are red shifted, they are moving away from us. galaxies seem to be moving away from us in all directions. the further away a galaxy, the large the redshift, the faste it is moving
How does the red shift theory support the Big Bang theory?
redshift tells us:
if distant galaxies are red shifted, they are moving away from us. galaxies seem to be moving away from us in all directions. the further away a galaxy, the large the redshift, the faster it is moving
When galaxies move further way faster, it suggests that at one instance in the past, all the galaxies were in the same position. The outward movement of speed of the galaxies are constant within this theory.
Calculating speed and distance of galaxies
Change and wavelength/wavelength of reference galaxy= Velocity of galaxy/speed of light
Red shift and light received from galaxies
The light emitted from distant galaxies, is red shifted, and the wavelength is longer than expected, which tells us that they are moving away from us (red shift is the light received form galaxies at different distances away from earth)
Galaxies appears to be moving away from us all directions and the father away from us. A galaxy is the bigger the red shift, which tells us that the further away a galaxy is the faster it is moving.
