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Science 9

Science 9 · Worksheets

Space exploration

Ten questions of mixed difficulty, covering Space exploration. Print it, or work through it on screen — the answer key starts on its own page.

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Space exploration

Science 9 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. After six months on the space station, an astronaut has lost some bone and muscle mass. The main cause is

    1. a) microgravity, since bones and muscles no longer bear weight
    2. b) radiation, since the station is above the atmosphere
    3. c) recycled water, since it has lost the calcium and minerals bones need
    4. d) the vacuum, since there is no air pressure on the body

  2. In the spectrum of a distant galaxy, the dark lines are shifted toward the red end compared with the same lines measured in a lab on Earth. This tells astronomers the galaxy is

    1. a) hotter than the Sun
    2. b) moving away from us
    3. c) moving toward us
    4. d) made of new elements

  3. The Sun is an average-mass star. At the end of its life it will become

    1. a) a black hole
    2. b) a neutron star
    3. c) a white dwarf
    4. d) a supernova

  4. A star chart says a planet will be at altitude 30° and azimuth 90°. Where should you look?

    1. a) East, one third of the way down from overhead
    2. b) East, one third of the way up from the horizon
    3. c) West, one third of the way up from the horizon
    4. d) North, one third of the way up from the horizon

  5. A communications satellite in geosynchronous orbit

    1. a) orbits once every 90 minutes, very close to Earth
    2. b) orbits the Sun instead of orbiting the Earth
    3. c) orbits once a day, keeping pace with Earth's spin
    4. d) does not move at all; it floats in one place

  6. Space debris is a serious hazard mainly because

    1. a) large pieces fall to Earth and often injure people
    2. b) the pieces pull satellites out of orbit with their gravity
    3. c) even small pieces move fast enough to wreck a satellite
    4. d) the pieces block sunlight from reaching Earth's surface

  7. Many cultures, including many First Nations, tracked the seasons by which stars could be seen after sunset. This works because

    1. a) the stars move much closer to Earth during certain seasons of the year
    2. b) Earth's orbit brings different stars into the night sky over a year
    3. c) the stars themselves change their positions every few months
    4. d) Earth's spin speeds up in summer and slows down in winter

  8. Astronomers measure two stars' positions against distant background stars in January and again in July. Star M shifts a lot; star N barely shifts. Which conclusion follows?

    1. a) Star M is closer to Earth than star N
    2. b) Star M is moving faster than star N
    3. c) Star M is larger and brighter than star N
    4. d) Star N is closer to Earth than star M

  9. Radio signals travel at the speed of light, which covers 1 AU in about 8.3 minutes. A probe at Saturn, 9.5 AU from the Sun, radios Earth while Earth is directly between Saturn and the Sun. About how long does the signal take?

    1. a) about 87 minutes
    2. b) about 1 minute
    3. c) about 71 minutes
    4. d) about 79 minutes

  10. A light-year is a measure of

    1. a) time: how long one year lasts out in space
    2. b) distance: how far light travels in one year
    3. c) speed: how fast light moves through space
    4. d) brightness: how much light a star gives off

Answer key · Space exploration

Science 9 · maddyhelps.com

  1. a) microgravity, since bones and muscles no longer bear weight — Bones and muscles stay strong by working against gravity; in orbit they barely have to, so the body lets them weaken, which is why station crews exercise about two hours a day. Radiation is a real hazard as well, but its main danger is damage to cells and DNA, not bone loss.
  2. b) moving away from us — Light from a source moving away is stretched to longer wavelengths, which shifts it toward red. A shift toward blue would mean it is approaching, and the lines still match known elements, which is how the shift can be measured at all.
  3. c) a white dwarf — A star of the Sun's mass swells into a red giant, sheds its outer layers and leaves its hot core behind as a white dwarf. Only stars many times more massive end in a supernova, leaving a neutron star or a black hole.
  4. b) East, one third of the way up from the horizon — Azimuth is the compass direction measured clockwise from north, so 90° is east. Altitude is the angle up from the horizon, and 30° is a third of the way to the point straight overhead at 90°.
  5. c) orbits once a day, keeping pace with Earth's spin — At about 36 000 km up, one orbit takes a day, the same as Earth's rotation, so the satellite stays over the same region and a dish can point at it without moving. It is travelling very fast; it only looks still from the ground.
  6. c) even small pieces move fast enough to wreck a satellite — Objects in low orbit travel at several kilometres per second, so even a paint fleck can chip a window and a loose bolt can destroy a satellite. Most debris that falls burns up in the atmosphere, and injuries on the ground are extremely rare.
  7. b) Earth's orbit brings different stars into the night sky over a year — As Earth travels around the Sun, the night side faces a different part of space, so the visible stars change through the year in the same order every year. The stars have not moved; our viewpoint has, which is what makes them a reliable calendar.
  8. a) Star M is closer to Earth than star N — This is parallax: as Earth moves to the other side of its orbit, nearby stars appear to shift more against the background than distant ones do. Hold up a finger and look with one eye, then the other; the closer the finger, the bigger the jump.
  9. c) about 71 minutes — With Earth between them, the gap is 9.5 − 1 = 8.5 AU, and 8.5 × 8.3 ≈ 71 minutes. Using 9.5 AU forgets that Earth is already 1 AU from the Sun, and adding the 1 AU puts Earth on the far side of the Sun instead.
  10. b) distance: how far light travels in one year — Despite the word year, a light-year is a distance, about 9.5 trillion km. A star 4 light-years away is one whose light took 4 years to reach us, so we see it as it was then.