The Universe -- Year 10 Flashcards
1 pc = ___ ly = ___ km
___ ly = ___ km
1 pc = 3.26 ly
3.26 ly = 9.461 km
A singularity is…
an infinitely dense point of matter that existed before the Big Bang.
Define anti-matter.
Particles that have properties opposite to that of normal matter.
How much time after the Big Bang did the particles of matter and anti-matter annihilate each other?
0.001 second.
What does the “Big Bang” refer to?
The rapid expansion of the initial singularity.
Define antimatter.
Particles that have properties opposite to that of normal matter.
What happened 3 minutes after the Big Bang?
Protons and neutrons combined to form atomic nuclei, about 75% hydrogen, 25% helium and a small fraction of lithium.
When was all the matter and energy to ever exist formed?
3 minutes after the Big Bang.
What happened 5,000 years after the Big Bang?
Atoms formed!
3 minutes - 5,000 years after the Big Bang, the universe was…
A plasma of hydrogen, helium, and lithium nuclei and free electrons.
The universe formed ___ years after the Big Bang.
1 billion (1,000,000,000)
What is redshift?
A change in light’s wavelength towards the red end of the visible spectrum.
Explain the cosmological red shift of stars.
Cosmological red shift, or red shift, is the shift of light coming from stars towards the red end of the spectrum. It is similar to the doppler effect, which describes the lengthening of shortening of waves emanating from a moving object. For example, an ambulance moving towards a person will have a higher pitch than an ambulance moving away from a person, because the sound waves are being shortened by the ambulances forward motion. The doppler effect can’t be applied to cosmological red shift because light does not travel through a medium like sound does. However the principle of the doppler effect can explain red-shift. When the fabric of space between stars expands, the stars begin to move away from each other. Hence, the light observed from one star coming from the other will be red-shifted, because the wavelengths are lengthening– similar to how the sound waves were longer when the ambulance was moving away from the person in the given example. Cosmological red-shift can be used as evidence for the Big Bang theory, as it suggests that the universe is expanding (stars are moving away from each other due to the expansion of space between them).
What is the CMBR?
The left-over heat radiation from the Big Bang, which has redshifted due to the expansion of the universe. Was originally released 100,000 years after the Big Bang as UV and visible light when the universe cooled enough to allow radiation to pass through it.
Why do images of the CMBR show clumps of matter?
Because the universe was not of uniform density when the CMBR was released.
Which element are stars mostly made up of?
Hydrogen.
In the centre of stars, ____ atoms fuse together to form ___ atoms. This reaction releases a lot of energy, including ____.
In the centre of stars, hydrogen atoms fuse together to form helium atoms. This reaction releases a lot of energy, including visible light.
The release of energy pushing outwards from the core of stars is caused by ____.
Nuclear fusion (i.e. hydrogen to helium).
What forces balance each other out when a star is fusing hydrogen in its core?
The inward force of gravity and outward force of nuclear fusion.
Stars are essentially hot balls of gas consisting of different elements. Depending on their initial mass, they evolve in different ways. However, they all start off as (1)____ originating from (2)_____.
(1) Protostars
(2) Nebulae
Explain why the size of a star impacts its life-cycle.
A large star fuses hydrogen more quickly and has more gravity. This means it has a shorter life-span and more intense events, like a super-nova rather than a planetary nebula, or the formation of a black hole, occur.
What main factor determines the stages a star goes through?
Its mass.
Compare and contrast the size of a sun-like star and a massive star.
A Sun-like star, or a small star, and a massive star both originate from nebulae, which are interstellar regions of gas and dust. The force of gravity causes the nebula to contract into a protostar. A Sun-like star will form into an average-sized star. The Sun is only 1 solar mass, whereas stars bigger than 7 solar masses are considered large. The Sun will turn into a red giant, whereas a large star will turn into a red supergiant. This transformation, in both cases, is caused by the force of nuclear fusion releasing energy that causes the star to expand outwards (as it is greater than the force of gravity). However, as the rate of nuclear fusion slows, the stars transform again. This process happens more quickly and intensely in large stars, because gravity acts more strongly on them, and also because hydrogen fuses more quickly in their cores. In large stars, therefore, when the forces of energy become imbalanced, gravity causes the star to rapidly contract and then explode, resulting in a supernova. This is known as a supernova, and leaves the core of the star as an extremely dense neutron star. In supermassive stars, a black hole is formed due to the total collapse of the core. On the other hand, in small stars, the energy released by nuclear fusion exceeds the inward force of gravity, and one last burst of energy is released. This forms a planetary nebula as the outer layers puff outwards. When these are lost into space, the core remains as an extremely hot, dense and small white dwarf.
As gravity pulls matter towards other matter, a sphere forms. Why?
Only a sphere allows every point on its surface to have the same distance from the centre, so that no part of the object can further ‘fall’ toward its centre. Gravity just keeps on pulling.
What’s a nebula?
An interstellar region of gas and dust.
What’s a neutron star?
An extremely dense star left over after a supernova.
