Stars & the Universe (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Physics): Flashcards
Exam code: 0654 & 0973
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- FrontThe Sun as a Star
What two elements is the Sun mostly composed of?
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Cards in this collection (28)
What two elements is the Sun mostly composed of?
The two elements the Sun is mostly composed of are hydrogen and helium.
True or False?
The Sun is a planet at the centre of the Solar System.
False.
The Sun is a medium-sized star which lies at the centre of the Solar System.
Name the main regions of the electromagnetic spectrum in which the Sun radiates its energy.
The Sun radiates most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum.
Define nuclear fusion. (Extended Tier Only)
Nuclear fusion is the joining of two smaller nuclei to form one larger nucleus, releasing a huge amount of energy.
Where do nuclear fusion reactions take place in a star? (Extended Tier Only)
Nuclear fusion reactions take place in the centre of a star.
How are all stable stars powered? (Extended Tier Only)
All stable stars are powered by nuclear fusion reactions, in which hydrogen nuclei fuse to form helium nuclei.
Define the Milky Way.
The Milky Way is one of the many billions of galaxies making up the Universe; it contains billions of stars, including the Sun.
What is the difference between a galaxy and the Universe?
A galaxy is a large collection of billions of stars, whereas the Universe is a large collection of billions of galaxies.
Define a light-year.
A light-year is the distance travelled by light in one year.
What is the approximate diameter of the Milky Way?
The diameter of the Milky Way is approximately 100 000 light-years.
Define nebula.
A nebula is a giant interstellar cloud of gas and dust from which stars form.
True or False?
All stars form from a cloud of gas and dust which becomes a protostar and then a stable star.
True.
All stars follow the same initial stages in their life cycle:
Nebula (cloud of gas and dust)
Protostar
Stable star
How does a protostar form?
The gravitational attraction within a nebula pulls the particles closer together until a hot ball of gas forms, known as a protostar.
When does a protostar become a stable star?
A protostar becomes a stable star once it is hot enough and the forces inside the star become balanced.
What determines the final stages of a star's life cycle?
The final stages of a star's life cycle depend on its mass.
What stages complete the life cycle of a small mass star after the stable star stage?
A small mass star (one with a similar mass to the Sun) finishes its life cycle in the following stages:
Red giant
Planetary nebula
White dwarf
How does a red giant form?
A red giant forms when a small mass star reaches the end of its life and the outer layers of the star expand and cool.
Define white dwarf.
A white dwarf is formed when the core of a small mass star collapses; it is found at the centre of a planetary nebula.
True or False?
A large mass star will eventually explode as a supernova and become a white dwarf.
False.
A large mass star will explode as a supernova, leaving behind a neutron star, or a black hole if the star has a very large mass.
Define supernova.
A supernova is an exploding red supergiant.
What is the difference between a neutron star and a black hole?
A neutron star is formed when the core of a large mass star collapses.
A black hole is formed when the core of a very large mass star collapses and is more dense than a neutron star.
True or False?
The nebula from a supernova may form new stars with orbiting planets. (Extended Tier Only)
True.
The nebula formed from a supernova may form new stars with orbiting planets, creating new planetary systems.
Where are the heaviest elements formed? (Extended Tier Only)
The heaviest elements (those heavier than iron) are formed during a supernova and are ejected into space.
Define the Big Bang theory. (Extended Tier Only)
The Big Bang theory states that the Universe began around 13.8 billion years ago from a single point of high density and temperature, and has been expanding ever since.
True or False?
The Universe is currently contracting. (Extended Tier Only)
False.
The Universe continues to expand as a result of the initial explosion, known as the Big Bang.
What happened to the Universe as it expanded? (Extended Tier Only)
As each point moved away from the others, the Universe began to cool.
Define redshift. (Extended Tier Only)
Redshift is the increase in the observed wavelength of light from a source that is moving away from an observer.
How does redshift provide evidence for the Big Bang theory? (Extended Tier Only)
Light from distant galaxies is redshifted, which shows they are moving away from us.
This means the Universe is expanding, so it must have been smaller in the past and have begun from a single point.
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