Download Science 09 Space Review 1. Know what a light year is

Science 09 Space Review
1. Know what a light year is and be prepared to do calculations involving light years (if a star is 100E6
light years away, how long does it take the light to reach earth?)
It takes 100E6 years for the light from something 100E6 light years away to reach us
d = vt
100E6 ly = (light speed)(100E6 years)
One light year is distance it takes light to travel one year
d = vt = (3E8 m/s)(365.25 days*24 h/day*60 min/h*60 sec/min) = 9.5E15 m
2. Given the solar system data, you should be able to determine scale model distances for ANY planet in
the solar system (or indeed, any celestial object).
Example: If earth is at 10 m in a model, where is Jupiter in the model?
Planets distance = planet's model distance
earth's distance
earth's model distance
778330000 km
149600000 km
= jupiter's model distance
10 m
778330000 km
149600000 km
10 m = jupiter's model distance
10 m
10 m
52 m = jupiter's model distance
3. Calculating orbital speeds of any planet
speed = distance
time
The distance for an orbit is given by 2πr (where r is the orbital radius)
Period is the time to complete one orbit
speed =
2πr
period
Example: Neptune is 4 504 300 000 km away from the sun and it takes 60
190 days to orbit the sun. How fast is Neptune going (answer should
be in km/s)
speed = 2(3.14159)4 504 300 000 km
60 190 (86 400) s
speed = 5.4 km/s slower than earth since force of gravity driving
Neptune around the sun is weaker than for earth
4. Don't forget how to deal with scientific notation on your calculator.
8.17×1013 ( = 81 700 000 000 000)
On a TI-30X calculator, you type: 8.17 EE 13
This shows on the screen for some TI calculators: 8.1713
5. You should be aware of the different types of 'light' that we use to observer and detect celestial objects:
visible light, infra red, ultra violet, radio waves, x-rays, gamma rays (page 382-385). You should know
about the signficance of red shift and blue shift. Do page 390: 4, 6-9
4. Visible light spectrum is ROYGBIV – the colours of light our eyes can detect (red is big wavelength,
blue is short wavelength)
6. Red shift is specifically about the colour we see when objects are moving away from us (red shift).
Spectral shifting is more general (could be red or blue shift)
7. Blue shift tells us the object is approaching us (getting closer), red shift tells us the object is moving
away from us (duck on page 383)
8. Look at the duck on page 383, the trailing waves are bigger indicating a red shift (for light)
9. Every element has a finger print (unique atomic spectrum – page 383)
6. Life cycle of stars (go through the handout) There are basically two paths (or three in our textbook) that
can be taken. You should understand the life cycle of stars (handout you were given). Review the
questions you were previously given (handout). (page 352-358; Do page 431 #6-7, pg 432 #19)
a) There are three possible life paths a star can take. What property of a star determines which path it
will take?
b) At which stage is our sun in it's life cycle?
c) Why is a red giant hotter (in the core) than our sun?
d) Why does a red giant collapse when fusion ceases?
e) What is so bizarre about a neutron star? 12 km across and heavier than the sun
7. You should be able to work with numbers expressed in scientific and exponential notation.
a) 2.5E3 = 2500
b) 3.5E-5 = 0.000 035
c) 3.0E8 = 300 000 000
d) 25E19 × 18E11 = 450E30 = 4.4E32
e) 16E10 ÷ 2E6 = 8E4
8. You should be able to use the equation speed = distance/time to calculate one of the variables
if the other two are given. Do page 431 # 14
a) How far is the moon if it takes 2.6 seconds for light to travel from earth to the moon and back. The
speed of light is 3.00E8 m/s. Ans: 3.9E8 metres
b) If a star is 25 million light years away, how long does it take light from that star to reach earth? Ans:
25 million years
c) How long would it take a spaceship travelling at 10 km/s to reach Mars (a distance of 78E6 km from
earth)? Express your answer in seconds, hours and days.
Ans 7,800,000 s, 2167 h, 90 days
9. Explain what gravity assist is. Use a drawing and the concepts we learned in class about elliptical orbits
and gravitational attraction.
10. Explain why we have seasons (pg 317, DO page 325 #2,3; page 431 #13). A diagram is very useful.
11. Explain why we have night and day and why the sun rises in the east and sets in the west (page 316, DO
page 325 #1).
12. What are the phases of the moon and how do we explain it? (page 318, DO page 325 #6)
13. What are two technologies that will speed up space travel. Explain the scientific principles behind these
two technologies (from the video handout).
14. How is the fact that according to Einstein, the clocks slow down at higher speeds important for the GPS
satellite system?
15. You should understand the basic structure of the solar system (pg 332-333): sun, terrestrial planets,
asteroid belt, gas giants (You should know in detail the 3 objects you used in your solar system
assignment). Which planets move faster? Why do some planets move faster than others? Which
planets are hot, which planets are cold? (pg 328-340) Do page 432 #20
16. Write down possible fusion equations for fusion reactions that occur during the life cycle of stars.
Massive stars burn a succession of elements. Iron is the most stable element and cannot be fused further.
17. You should be aware of the relative sizes of the following (listed from large to small):
universe
galaxy
solar system
star
planet
asteroid
comet
18. Take home question. Refer to Pages 401-425 of your textbook are about benefits (402-414) and costs
(415-425) of space research. You may also makeup your own question that includes at least 15 science
concepts/facts.
Your take home question is to answer thoughtfully:
Is it worthwhile for the government to fund research in space exploration?
You need to look at both the pros and cons of this issue. In addition, you need to look at
different viewpoints
♦ scientist
♦ politician
♦ average citizen
♦ engineer
♦ taxpayer
♦ economist, etc
Grading (out of 20):
10: science concepts
5: at least THREE different viewpoints represented
5: how you present and use your evidence to support your argument
Answer to 6: a) the mass of a star determines which path a star takes (see page 354)
b) Our sun is in adulthood http://sunshine.chpc.utah.edu/Labs/StarLife/starlife_main.html
c) A red giant fuses helium into carbon and this requires higher temperatures than fusing hydrogen into helium
which is what our sun does
d) Once a star runs out of fuel for fusion, the thermal pressure outwards disappears and the gravitational
attraction inward causes the collapse
e) What is so bizarre about a neutron star? See page 357 Figure 10.14
Answer to #14: Since clocks on the fast moving, orbiting satellite would be slower than the clocks on earth, the
satellite clocks have to be set ahead before they are launched into space. That way, both the satellite clock and
the earth clocks are in synch and the GPS will be accurate.
Answer to #16 (NOTE: use the periodic table and the mass number for each element):
4 (1H) → 4He + energy (our sun) 15E6°C core temperature
15E6°C = 15×106°C = 15,000,000°C
3 ( 4He) → 12C + energy (red giant) 100E6°C core temperature
100E6°C = 100,000,000°C
2 ( 12C) → 24Mg + energy (red giant)
How do you fuse oxygen given the elements available?
4 (4He) → 16O
How would you fuse carbon into iron?
4 (12C) + 2 ( 4He) → 56Fe
14 (12C) → 3(56Fe)