Download That is an irrelevant question, Ms Gajda, there was no

Science 10F
Astronomy
Name: ____________________________
Origin of the Universe Review Questions
1. What is Hubble’s Law?
The farther an object is (from Earth), the faster it moves away (from Earth)
2. What did Edwin Hubble observe in space to show that the universe is
expanding? Explain.
He observed a “red shift”, which is that he saw that as light moved away
from its source, the light became more and more red.
3. The light spectrum of a newly discovered star is found to have shifted toward the
red end of the spectrum. What does this tell us about the star’s motion?
The new star is moving away from the Earth.
4. How is the Big Bang Theory different from the Steady State Theory?
Big Bang states that the universe started with a big explosion 15 billion
years ago. Steady State states that the universe always existed (no
beginning or end).
5. What is the largest piece of evidence which supports the Big Bang Theory?
Hubble’s Law, and that the universe is expanding
6. Thinking critically – Within the group of galaxies close to the Milky Way,
some galaxies show a red shift and others show a blue shift. What does this
suggest about the movement of the galaxies?
The galaxies showing red shift are moving farther away; the galaxies
showing blue shift are moving closer to our galaxy.
7. According to the Big Bang Theory, how long ago did the universe begin?
15 billion years ago
8. Outline the main steps in the Big Bang Theory.
1. Big Bang
2. In the first second:
a. Time is created
b. Universe starts expanding and cooling
c. Temp is 1032deg and cools to 10,000,000deg
Science 10F
Astronomy
Name: ____________________________
d. Quarks, protons and neutrons (hydrogen) are created
3. Helium is produced starting at 3 minutes
4. Atoms are formed after 500,000 years
5. Gravity begins forming stars and galaxies after 1 billion years
9. What existed before the Big Bang? What was created at the Big Bang?
That is an irrelevant question, Ms Gajda, there was no time before the Big
Bang therefore is there no “before”.
Time, space, matter, energy were created with the Big Bang.
10. Was the universe large or small when the Big Bang created it? Explain.
Universe was infinitely small just after the Big Bang and it started
expanding and cooling afterward.
11. Write a definition of luminosity.
How bright, how much light is emitted by a star
12. A colour photograph of the sky will show that stars actually differ in colour. How
can the colour of starlight reveal the temperature of a star?
Blue means that a star is very very hot, red means that it’s still hot, but just
not as much as a blue star.
13. What are the three groups of stars found on the Hertzsprung-Russell diagram?
How are these types of stars different?
White dwarfs – very dense, but dim, can’t see them without telescope
Giants and Supergiants – really, really big; very, very bright; live short lives
Main-sequence stars – 95% of all stars; adulthood of stars; wide range of
sizes, temperatures and luminosity
14. You notice a star in the sky which looks a little blue. What can you conclude
about the temperature of the star?
This star is very hot (10,000 – 50,000 deg)
Science 10F
Astronomy
Name: ____________________________
15. Thinking critically – why might a cooler star appear to be brighter than a
hotter star?
That cooler star could be bigger than the hotter star therefore it would
appear brighter from Earth. The cooler star could also be closer than the
hotter star.
16. Out of which material do stars begin to form?
Hydrogen/gas and dust found in nebulae
17. What are the nuclear reactions that take place in a star’s centre?
The collision and fusion of hydrogen nuclei – produce helium
18. What causes a main sequence star to become a red giant?
The nuclear reactions cause the core of the main sequence star to expand
and grow larger. Eventually, the star will get so big, it will be classified as
a red giant.
19. Which force is active all the time, from creating a star to causing its ultimate
end?
Gravity
20. Why does a supernova occur? What happens in a supernova?
A supernova occurs when the core of a giant/supergiant star turns to iron
and nuclear reactions no longer occur.
The centre of the star collapses and the outer layers explode, leaving either
a neutron star or black hole.
21. What property of a star has the greatest effect on what will happen to the star
after it dies? Explain.
Mass – a collapsed star less than 3x Sun’s mass turns into a neutron star
- A collapsed star is greater than 3x Sun’s mass turns into a black hole
22. What is the difference between a neutron star and a black hole?
Neutron star is made of neutrons and does not emit light, but does emit
radio waves.
Science 10F
Astronomy
Name: ____________________________
Black holes are stars whose centre has collapsed twice (once during
supernova, again after supernova). Gravity is so strong that neither radio
waves nor light waves can escape.
23. Describe pulsar stars. What is a good analogy for a pulsar?
Lighthouse is a good analogy because a pulsar star is a star that spins very
quickly and emits radio waves in a beam. Therefore, Earth can only detect
the radio waves in pulses (when the beam is pointing to Earth).
24. What is a white dwarf and how is it formed?
White dwarf is a star at the end of a main sequence star’s life. The main
sequence star expands into a red giant. The red giant’s centre will collapse
to form the white dwarf; its outer layers form a planetary nebula.
25. What is the difference between a nebula and a planetary nebula?
A nebula is a cloud of dust and gas where stars are born. A planetary
nebula is a cloud of dust and gas surrounding a dying star.
26. There are 3 types of dwarf stars. Name and briefly describe what is different
about each.
Red dwarf – low mass (more than brown), sustain nuclear reactions, burn
fuel very slowly, live for more than a trillion years
Brown dwarf – very low mass, no nuclear reactions, aka failed stars, warm
(not hot) and emit light
White dwarf – dying star, no nuclear reactions, heat is leftover from prior
life