physics topic 8 Flashcards
what is thought to be at the centre of the milky way
a massive black hole
The Universe is thought to have formed how many years ago
13.7 billion years ago.
The solar system formed how many years ago
4.6 billion years
what is The solar system
The solar system is any object that is bound by gravity to a Sun.
All objects in the solar system orbit The Sun.
in our solar system there is what
- one star – the Sun
- eight planets
- dwarf planets
- natural satellites called
moons that orbit planets.
Other objects in
The solar system include:
* Comets
* Asteroids
* Satellites
how does a solar system from
(a) The universe contains ‘clumps’ of
dust and gas each called a nebula.
(b) Gravitational attraction pulls this
dust and gas together.
(c) Forming the Sun (a star).
(d) Fusion reactions lead to an
equilibrium between the
gravitational collapse of the star and
the expansion of a star due to fusion
energy.
(e) The remaining parts of the solar
system form from the remaining
dust and gas.
why do small stars live longer than big stars
Small stars live a lot longer than massive stars as they use up their fuel more slowly.
The Sun will be a
main sequence
star for how long
20 billion years.
describe the life cycle of a small star
1) Nebula (Cloud of gas and dust)
2) protostar
3) Main sequence star
4) Red Giant
5) white dwarf
6) black dwarf
describe the life cycle of a large cycle
1) Nebula (Cloud of gas and dust)
2) protostar
3) Main sequence star
4) Red super Giant
5) supernova
6) neutron star / black hole
describe the Life of a star
- cloud of gas and dust (nebula)
- pulled together by gravity
- causing increasing temperature (to start fusion)
- becomes protostar
- hydrogen nuclei fuse to form helium nuclei
- fusion produce new elements
- star becomes main sequence
describe the Death of a star
- Hydrogen runs out
- helium nuclei fuse to make heavier elements
- up to iron
- star expands
- becomes red super giant
- star collapses rapidly and explodes
- called a supernova
- creating elements heavier than iron
- and distributing them throughout the universe
- leaving behind a neutron star
- or a black hole.
The Sun, releases energy though what
nuclear fusion reactions in the core.
describe how the Sun releases energy
Isotopes of Hydrogen forced together under high temperature and pressure.
Nuclear fusion occurs to form Helium and a neutron.
A tiny amount of mass is converted into a
large amount of energy, So stars emit a lot of energy.
describe Fusion
Light nuclei
Fuse to make a heavier nuclei
Some mass gets converted into energy
describe equilibrium in a star
Fusion produces thermal pressure
(pushes out)
Gravity pulls inwards
Leads to equilibrium
To avoid being pulled into the sun, a planet must be what
must be travelling faster, the closer
it is to the sun. This is why Mercury’s orbit of the sun takes 3 Earth months
whereas it takes Neptune 165 Earth years to orbit the sun.
In a perfectly circular orbit what happens
a body will travel at constant speed to maintain its
orbital distance.
why don’t things have a circular orbit
gravity is constantly changing the direction of the body. As velocity
depends on speed and direction, the velocity is constantly changing even
though speed remains the same (only direction changes)
why does red shift happen
Red shift happens because galaxys are moving away from us at high speed,
causing the wavelengths of light to be increased.
summarise what red shift is
- Red light has a longer wavelength than blue light.
- Most distant galaxies show an increase in wavelength of light.
- The further away the galaxies the faster they are moving and
the bigger the increase in wavelength. - This effect is called the RED-SHIFT.
- The observed red-shift provides evidence that the universe is expanding and supports the Big Bang theory.
how does red shift support the big bang theory
- light from galaxies shifted towards red end of spectrum
- the further away the galaxy, the greater the red shift
- wavelength (appears) to increase
- this shows that galaxies are moving away from us
- this suggests that Universe is expanding from initial point
- Cosmic Microwave Background Radiation (CMBR) can only be explained by the big bang
how do we know galaxy’s are moving away from us at different speeds
Absorption spectra from stars in every galaxy would look the same if all the
galaxies were a fixed distance from the Earth. Galaxies have different amounts of
red shift which means they are moving away from us at different speeds.
give the strengths for the Balloon model
as the balloon expands, dots get further apart, representing the galaxies moving apart
give the weaknesses for the Balloon model
dots are only on the surface of the balloon, galaxies are throughout the universe
there is a limit to how far the balloon can expand
what is the big bang theory
Universe expanded from a single point of matter around 13.7
billion years ago.
Over the last century what had been discovered about the universe
- The age of the Universe.
- The Universe is more than just our galaxy.
- The size of the Universe.
- There are probably billions of other planets beyond our Solar System.
- The Universe is expanding.
- Cosmic microwave background radiation supporting the Big Bang theory.
what do we not understand about the universe
- Dark matter and dark energy – continued expansion and acceleration of the Universe suggests there must be a lot more matter and energy than we can see. This is described as dark matter/energy that we have yet to find.
- Fate of the Universe. Is the Universe going to continue forever or
collapse back to a point and start again? - Is our Universe just one of a series of multiverses?
- Does life exist anywhere else in the Universe?
