P16 - Space Flashcards
What is the Big Bang Theoty?
The theory that states the to begin with all the matter in the universe was concentrated into a single incredibly dense point. This began to enlarge rapidly in a hot explosion. The universe has been expanding ever since. Space, time, and matter were created in the big bang
What is a black dwarf?
A star that has faded out and gone cold
What is a black hole?
An object in space that has so much mass that nothing, not even light, can escape from its gravitational field
what is centripetal force?
The resultant force towards the centre of a circle acting on an object moving in a circular path
What is cosmic microwave background radiation (CMBR)?
electromagnetic radiation that has been travelling through space ever since it was created shortly after the Big Bang as gamma radiation, however the doppler effect has caused them to now appear as microwave radiation
What is dark matter?
Matter in a galaxy that cannot be seen. Its presence is deduced because galaxies would spin much faster if their stars were their only matter
What is main sequence?
The main sequence is the life stage of a star during which it radiates energy due to fusion of hydrogen nuclei in its core
What is a neutron star?
The highly compressed core of a massive star that remains after a supernova explosion
What is a protostar?
The concentration of dust clouds and gas in space that forms a star
What is a red giant?
A star that has expanded and cooled, resulting in it becoming red and much larger and cooler than it was before
What is a red supergiant?
A star much more massive than the sun will swell out after the main sequence stage to become a red supergiant before it collapses
What is red-shift?
Increase in the wavelength of electromagnetic waves emitted by a star or galaxy due to its motion away form the observer. The faster the speed of the star or galaxy, the greater the red-shift is
What is a supernova?
The explosion of a massive star after fusion in its core ceases and the matter surrounding its core collapses onto the core and rebounds in an explosion
What is a white dwarf?
A star that has collapsed from the red giant stage to become much hotter and denser
What is a planet?
A planet is an object in orbit around a star that has cleared their orbit of other objects
What are moons?
A body in orbit around a planet
What is a comet?
Frozen rocks that move around the sun in orbits that are elliptical in shape. These elliptical orbits take them far away from the sun. You can only see them when they return near the Sun because then they heat up so much that they emit light.
Why can you only see a comet when it is near the sun?
You can only see them when they return near the Sun because then they heat up so much that they emit light.
What are meteors?
Small bits of rock that burn up when they enter the earths atmosphere
What are minor (dwarf) planets?
Dwarf planets have not cleared their orbit of other objects.
What are asteroids?
Asteroids are objects too small and uneven to be planets, usually in near-circular orbits around the Sun and without the ice present in comets
Describe the birth of a star:
It begins with a large cloud of dust and gas in space known as a stellar nebula. The stellar nebula is pulled together by their gravitational attraction. As these clouds join, becoming more and more dense, a protostar is formed. As the protostar becomes denser it gets hotter, this energy causes lighter nuclei to fuse together, energy is released from this fusion reaction so the protostar gets even hotter. Getting hotter and brighter, it begins to shine, giving birth to a main sequence star. The outward force from the nuclear fusion balances the force of the star’s gravity
How does a planet form?
The star’s gravity pulls smaller amounts of dust and gas together, forming planets in orbit of the star
Explain how main sequence stars are stable, and how the star becomes unstable.
A main sequence star is stable as the forces within it are balanced. The force of gravity acts inwards trying to make the star contract, the outward force of radiation from the nuclear fusion in its core trying to make the star expand. Energy released in the core keeps the core hot, so the process of fusion continues. Radiation such as gamma radiation flows out steadily from the core in all directions. These forces stay in balance until most of the hydrogen nuclei have fused to form helium nuclei, this causes the star to become unstable as there are no more hydrogen nuclei for hydrogen fusion
What force pulls the dust and gas together to form a protostar?
Gravitational attraction
State the 5 stages of the life cycle of a star the same size as our sun:
- Protostar
- Main Sequence Star
- Red Giant
- White Dwarf
- Black Dwarf
State the 5 stages of the life cycle of a star the much bigger than our sun:
- Protostar
- Main sequence star
- Red Super Giant
- Supernova
- Neutron star / Black hole
Explain why low mass stars remain in the main sequence for much longer than large mass stars
Stars with low masses remain in their main sequence stage for much longer, as their core is cooler than that of more massive stars, therefore fusion takes place at a slower rate
Explain the life cycle of a low-mass star:
- The star initially forms from a cloud of dust and gas known as a nebula
- Gravitational attraction pulls the dust and gas closer together to form a protostar
- When the protostar becomes dense enough, hydrogen fusion begins releasing large amounts of energy
- The outward pressure of nuclear fusion outwards balances the force of gravity inwards. This is known as a main sequence star
- As hydrogen begins to run out, the “main sequence” stage ends. The outer layers of the star swells into a red giant, it becomes red as the surface cools. However, the core continues to contract. Therefore fusion of helium and other elements occur. This means heavier elements (up to iron) are created in the core of a star
- When fusion stops no more radiation is released and the star ejects its outer layer of dust and gas, leaving a hot, dense solid core known as a White Dwarf Star
- As a white dwarf cools, it emits less and less energy. When it not longer emits a signifigant amount, it is called a black dwarf
Explain the life cycle of a high-mass star:
- The star initially forms from a cloud of dust and gas known as a nebula
- Gravitational attraction pulls the dust and gas closer together to form a protostar
- When the protostar becomes dense enough, hydrogen fusion begins releasing large amounts of energy
- The outward pressure of nuclear fusion outwards balances the force of gravity inwards. This is known as a main sequence star
- As hydrogen begins to run out, the “main sequence” stage ends. The outer layers of the star swells into a red supergiant, it becomes red as the surface cools. However, the core continues to contract. Therefore fusion of helium and other elements occur. This means heavier elements (up to iron) are created in the core of a star
- The star contracts and expands several times before exploding in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars
- The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star, this is an extremely dense object made only of neutrons. However, if the star is massive enough, it will become a black hole instead of a neutron star, this is a super dense point in space with such a strong gravitational attraction that not even light can escape it
How are elements up to Iron formed?
Nuclear fusion in the core of a red giant / red supergiant
How are elements larger than iron formed?
Heavy elements larger than iron are formed during a supernova explosion. The enormous force of the collapse fuses small nuclei into nuclei bigger than iron nuclei. The explosion also scatters the elements throughout the universe
