Stars and the origins of the Universe Flashcards
When was the Sun formed?
The Sun was formed about 4.6 billion years ago.
How was the Sun formed?
The Sun was formed from a thin cloud of dust, gas and ice called a nebula. All the materials in the nebula were pulled together by the force of gravity. It eventually started to spin and contract, and the temperature increased. At a few million degrees Celsius, nuclear fusion reactions started to occur, the temperature rose even higher and the new start began to emit its own light.
Where does the Sun’s energy come from?
The Sun’s energy comes from nuclear fusion reactions. The vast amount of energy produced is emitted as electromagnetic radiation.
What balance is the Sun in?
The Sun is in a delicate balance between the force of gravity trying to pull all matter towards its centre and the force produced by the EM radiation pushing its way out.
When does the nuclear fusion reaction in the Sun occur?
The nuclear fusion reaction in the Sun occurs when hydrogen nuclei fuse together to form a helium nucleus.
What does hydrogen become?
hydrogen -> helium + energy
What is the life-cycle of a normal star?
nebula - sun - red giant - white dwarf - black dwarf
What is the life-cycle of a massive star?
large nebula - star - super red giant - super nova - black hole or a neutron star
What is the Steady State theory?
The Steady State theory is the theory that the Universe;
- is expanding
- has unchanging density
- spontaneously created matter, especially hydrogen, from empty space to maintain the same density
- had no beginning and will never end
What is the Big Bang theory?
The Big Bang theory is the theory that the Universe:
- is expanding
- is finite and ever-changing
- was created about 14 billion years ago from an event called the Big Bang
- may have an end, depending on its density
What is CMB radiation?
CMB radiation is considered to be “left-over radiation” from the Big Bang.
How can CMB radiation be detected?
It can be detected by radio telescopes and is the same strength in all direction.
What is the red shift?
The spectrum of light from distant starts show the same pattern of dark lines, but the dark lines are shifted towards the red end of the spectrum.
How can we use the red-shift as proof that galaxies are moving away from us?
The light from all distant galaxies is red-shifted. This means that galaxies are all moving away from us and from each other. The Universe is expanding. The further away the galaxy, the greater the red-shift. Therefore, the most distant galaxies are moving away more quickly.
What is the evidence for the Big Bang theory?
- all galaxies show red-shift which means the Universe must be expanding
- the temperature of the Universe was predicted to be -270 degrees Celsius - this was confirmed by the COBE satellite in the 1990s
- the original radiation created in the Big Bang would have been gamma rays. Due to the expansion of the Universe, the Doppler effect has stretched the wavelength to become microwave radiation, with a wavelength of about 1mm
