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ST chapter only

Checkup • Chapter 9

1 Observations of the sky (pp. 274–282)

1. Certain astronomical phenomena can be seen with the naked eye while others must be observed with instruments. Which of the following phenomena can be observed with the naked eye?

a lunar eclipse

the Great Red Spot of Jupiter

a meteor crashing on Mars

the movement of the stars in the sky

Saturn’s rings

day and night on Earth

2. Name three instruments used to observe the night sky.

3. Which five planets were discovered through visual observation?

Mercury Venus Mars

Jupiter Saturn

4. Which two planets were discovered thanks to either the refracting telescope or the reflecting telescope?

Uranus Neptune

5. Define the terms astronomical unit and light year.

Astronomical unit: A unit of measurement equal to about 150 million kilometres, the average

distance between Earth and the Sun.

Observatory/Guide11071-B 1 CHECKUP OF CHAPTER 9

ANSWER KEY

Three of the following answers:

The eye; refracting telescope; reflector telescope; binoculars; radio telescope; radar; observatory; satellite;

space probe; space rocket; space shuttle; space station

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Light year: A unit of measurement equal to the distance light travels in one year, or about

9 500 billion kilometres.

6. What is the speed of light (km/s)?About 300 000 km/s (more precisely, 299 792 km/s), or about 1.08 billion km/h

7. The kilometre, the astronomical unit and the light year are three units of measurement used to calculate distances. Which would be used to calculate each of the following?

a) the distance between Jupiter and Mercury The astronomical unit

b) the distance between the Sun and thestar Rigel The light year

c) the distance between Earth and the Moon The kilometre

d) the distance between Gaspé and Rouyn-Noranda The kilometre

e) the distance between the Milky Way and Andromeda The light year

8. On April 3, 2024, Earth and Jupiter will be respectively 1.0 AU and 5.0 AUfrom the Sun.

a) How much further will Jupiter be from the Sun than Earth? Five times

b) Is this data sufficient to calculate the distance between Earth and Jupiter on that date? Use a diagram to explain your answer.No, because Jupiter is not necessarily on the same straight line as Earth and the Sun.

The distance between these two planets depends on their respective positions in their orbit.

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c) On that date, how many kilometres will separate Jupiter from the Sun?Jupiter will be 750 000 000 km from the Sun.

9. In 1987 an explosion of the SN1987A starwas observed. It was located 170 000 ly awayfrom our planet.

a) How long ago did this explosion occur? Explain your answer.Since this star is located 170 000 ly away from our

planet,

the light emitted by its explosion took 170 000 years to

reach our planet. Therefore, the star exploded 170 000

years ago.

b) How many kilometres separated Earth and SN1987A when it exploded?Show your calculations.

If: 1 ly 9 500 000 000 000 km

170 000 ly x km

Then:

At the time of its explosion, the SN1987A star was located 1 615 quadrillion kilometres from Earth.

Observatory/Guide11071-B 3 CHECKUP OF CHAPTER 9

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10. The Small Magellanic Cloud is a neighbouring galaxy. It is located about 200 000 ly away. Convert this distance to kilometres.1 995 000 000 000 000 000 km or

1 995 quadrillion km

2 The Earth in the Universe (pp. 283–292)

11. The Sun is a heat and light source for Earth and the entire solar system. Is the Sun a star? Explain your answer.Yes, because it is a celestial body that shines on its own.

12. For a long time, humans thought all celestial bodies revolved around Earth. We now know that is not the case. There is only one celestial body orbiting Earth.

a) What is it called? The Moon

b) What is its average distance from Earth? 384 000 km

13. How much time elapses between two full moons? 27.32 days

14. What phenomenon is at the source of the Sun’s energy?The nuclear reactions that occur at its core

15. How many times is the Sun’s diameter greaterthan Earth’s? About 109 times

16. Which planets in our solar system do not possess any known natural satellites?Mercury and Venus

CHECKUP OF CHAPTER 9 4 Observatory/Guide11071-B

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17. “My very eager mother just served us noodles” is a sentence used to remember the names and order of the planets. The first letter of each word corresponds to the first letter of each planet.

a) Identify the planets corresponding to the first letter of each word in the sentence.

M Mercury V Venus E Earth

M Mars J Jupiter S Saturn

U Uranus N Neptune

b) Indicate the average distance of each planet from the Sun.Mercury: 0.39 AU Jupiter: 5.20 AU

Venus: 0.72 AU Saturn: 9.54 AU

Earth: 1 AU Uranus: 19.19 AU

Mars: 1.52 AU Neptune: 30.06 AU

c) Identify the three dwarf planets and indicate their average distance from the Sun.Ceres: 2.77 AU Pluto: 39.55 AU Eris: 67.67 AU

18. A planet in our solar system is located at 4 500 000 000 km from the Sun.

a) What is the distance in astronomical units? 30 AU

b) Identify the planet. Neptune

19. Planets with a rocky surface, such as Earth, are also called terrestrial planets.

a) Which planets in our solar system are terrestrial planets? Mercury, Venus and Mars

b) Which dwarf planet also has a rocky surface? Ceres

c) What is the surface composition of the other two dwarf planets? Pluto and Eris: their surface is made of ice.

Observatory/Guide11071-B 5 CHECKUP OF CHAPTER 9

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20. It is not likely that spacecraft would be able to land on a planet with an orbit beyond that of Mars. To explore such planets, spacecraft must do flybys.

a) Which planets have an orbit beyond that of Mars?Jupiter, Saturn, Uranus and Neptune

b) Why are spacecraft not able to land on such planets?Because these planets have a gaseous surface.

21. Answer the following questions.

a) Why is the average surface temperature of Venus so high?Because its atmosphere is mainly carbon dioxide, a greenhouse gas.

b) Why does Mars appear red?Because of an abundance of ferrous oxide on its surface

c) Why does Neptune appear blue?Because of the presence of methane gas in its atmosphere

22. What is the difference between a comet and an asteroid? An asteroid is a celestial body of irregular shape in orbit around the Sun.

A comet is a celestial body covered in ice that releases gas and ice debris as its passes the Sun.

23. The Milky Way is the name of our galaxy.

a) What is a galaxy?It is a massive cluster of stars and matter that orbits its centre.

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b) How far away are we from the centre of our galaxy?26 000 ly

c) Approximately how many stars are in the Milky Way?Approximately 200 billion

d) What is our closest neighbouring galaxy?Canis Major

e) How far away is it from our galaxy?25 000 ly

24. The Andromeda galaxy is pictured at right.

a) Is it an elliptical, spiral or irregular galaxy?Elliptical

b) Is the Milky Way the same type of galaxy as Andromeda? If not, what type is it?No. The Milky Way is a spiral galaxy.

25. True or false?

TRUE FALSE

a) The Sun is located at the centre of the solar system.

b) The solar system is located at the centre of the Milky Way.

c) The Milky Way is at the centre of the Universe.

Observatory/Guide11071-B 7 CHECKUP OF CHAPTER 9

ANSWER KEY