Flashcards
Space
Flashcards do conjunto (21)
- 1Life Cycle of Stars 1Stars initially form from a cloud of dust and gas called a nebula
- 2Life Cycle of Stars 2The force of gravity pulls the dust and gas together to form a protostar
- 3Life Cycle of Stars 3The temperature rises as the star gets denser and more particles collide with each other. When the temperature gets high enough, hydrogen nuclei undergo fusion to form helium nuclei. This gives out huge amounts of energy, which keeps the core of the star hot. A star is born
- 4Life Cycle of Stars 4The star enters a long stable period where the outward pressure caused by the nuclear fusion that tries to expand the star balances the force of gravity pulling everything inwards. In this stable period it's called a main sequence star and it typically lasts several billion years. Sun is in the middle of this stable period
- 5Life Cycle of Stars 5Eventually the hydrogen begins to run out. The star then swells into a red giant (if it is a small star) or a red super giant (if it is a larger star). It becomes red because the surface cools. Fusion of helium (and other elements) occurs. Heavier elements (up to iron) are created in the core of the star
- 6Life Cycle of Stars 6A small to medium sized star like the Sun then becomes unstable and ejects its outer layer of dust and gas. This leaves behind a hot, dense solid core - a white dwarf
- 7Life Cycle of Stars 7As a white dwarf cools down, it emits less and less energy. When it no longer emits a significant amount, it is called a black dwarf
- 8Life Cycle of Stars 8Big stars, however, start to glow brightly again as they undergo more fusion and expand and contract several times, forming elements as heavy as iron in various nuclear reactions. Eventually, they'll explode in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars. Stars and their life cycles produce and distribute all naturally occurring elements
- 9Life Cycle of Stars 9The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star. If the star is massive enough, it will become black hole - a super dense point in space that not even light can escape from
- 10PlanetsLarge objects that orbit a star. There are 8 in our solar system. They have to be large enough to have 'cleared their neighbourhoods'. This means that their gravity is strong enough to have pulled in any nearby objects apart from their natural satellites
- 11Dwarf PlanetsLike Pluto. These are planet-like objects that orbit stars, but don't meet all of the rules for being a planet, e.g. size
- 12MoonsThese orbit planets. They're a type of natural satellite (not man made)
- 13Artificial satellitesSatellites that humans have built. Generally orbit Earth
- 14Solar SystemOur solar system is a tiny part of the Milky way galaxy. This is a massive collection of billions of stars that are all held together by gravity
- 15Gravity Provides the Force that Creates ObjectsThe planets move around the Sun in almost circular orbits (same goes for the Moon orbiting the Earth)
If an object is travelling in a circle it is constantly changing direction, which means it is constantly accelerating
This also means it is constantly changing velocity, but not speed
For an object to accelerate, there must be a force acting on it. This force is directed towards the centre of the circle
This force would cause the object to just fall towards whatever it was orbiting, but as the object is already moving, it just causes it to change its direction
The object keeps accelerating towards what it's orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle
The force that makes this happen is provided by the gravitational force between the planet and the Sun (or between the planet and its satellites) - 16What is a satellite?An object that orbits a second, more massive object
- 17Size of the Orbit Depends on the Object's SpeedThe closer you get to a star or planet, the stronger the gravitational force is
The stronger the force, the faster the orbiting object needs to travel to remain in orbit (to not crash into the object that it's orbiting)
For an object in a stable orbit, if the speed of the object changes, the size (radius) of its must do so too. Faster moving objects will move in a stable orbit with a smaller radius than slower moving ones - 18Red ShiftAll galaxies seem to be moving away from each other - universe is expanding
When we look at light from the most distant galaxies, we find that the wavelength has increased
The wavelengths are longer than they should be - they're shifted towards the red end of the spectrum. This is called red-shift
This suggests the source of the light is moving away from us. Measurements of the red-shift indicate that these distant galaxies are moving away from us (receding) very quickly - and it's the same result whichever direction you loo in
More distant galaxies have greater red-shifts than nearer ones. This means that more distant galaxies are moving away faster than nearer ones - 19Big BandAll the galaxies are moving away from each other at great speed - suggesting something must have got them going. That something was probably a big explosion - Big Bang
Initially, all the matter in the universe occupied a very small space. This tiny space was very dense and so was very hot
Then it exploded - space started expanding and the expansion is still going on - 20New TheoriesWhenever scientists discover new evidence, they have to either make a new theory or change a current one to explain what they've observed
There is still lots we don't know about the universe. Observations of supernovae from 1998 to the present day appears to show that distant galaxies are moving away from us faster and faster (the speed at which they're receding is increasing)
Currently scientists think the universe is mostly made up of dark matter and dark energy - 21Dark Matter and Dark EnergyDark matter is the name given to an unknown substance which holds galaxies together, but does not emit any electromagnetic radiation
Dark energy is thought to be responsible for the accelerated expansion of the universe
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- FlashCards sobre Space, criado por Jasmine Sillence em 19-02-2022.
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- Jasmine Sillence
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