Astronomical units, light-years and parallax

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Four plan cards, labeled A to D. Which plan would measure a nearby star's parallax, by Esme's reading?

   • Measure how bright it looks
   • Photograph it against far stars, then again six months later
   • Photograph it from two nearby towns on one clear, moonless night
   • Photograph it twice in one night
2. 2.

   “Parallax diagram:” Why can parallax not be used for very distant stars, by Jun's reading?

   • Their light is too old to use
   • Earth's orbit is too wide
   • Their shift is too tiny to measure
   • Far stars shift the most, so their images blur
3. 3.

   Distance (parsecs) = 1 ÷ parallax (arcseconds); smallest parallax 0.001; 1 parsec ≈ 3.26 light-years. A space telescope can measure parallaxes as small as 0.001 arcseconds. About how far away can it reach, by Kira's math?

   • About 1,000 parsecs, about 3,260 light-years
   • About 1,000 light-years
   • About 1 parsec
   • About 0.001 parsecs
4. 4.

   Luz's friend says a light-year is how long a star lives. Which response is best?

   • Agree: it is a star's life span
   • Disagree: it is a distance, about 9.46 trillion km
   • Agree: it is one year in space
   • Disagree: it is a speed
5. 5.

   Milo's cousin says the farthest stars show the biggest parallax. Which response is best?

   • Disagree: each star shows the same parallax shift against the background
   • Agree: a big parallax means a big distance
   • Agree: farther things move more
   • Disagree: nearer stars shift more, since distance = 1 ÷ parallax
6. 6.

   Distance (parsecs) = 1 ÷ parallax; 1 parsec ≈ 3.26 light-years. X: parallax 0.25; Y: 8 light-years. Star X has a parallax of 0.25 arcseconds. Star Y is 8 light-years away. Which is nearer, by Pia's math?

   • X, at 4 light-years
   • X, since 0.25 is a small number
   • They are the same distance
   • Y, at 8 light-years; X is about 13

7. Read this first

   Light travel times

   Trip	Time
   Sun to Neptune	about 4.2 hours
   Sun to Proxima Centauri	about 4.25 years

8. 7.

   Sunlight takes about 4.2 hours to reach Neptune and about 4.25 years to reach Proxima Centauri. About how many times longer is the trip to Proxima, by Ren's math?

   • About 9 × 10⁶ times longer
   • About 4 times longer
   • About the same; both are about 4
   • About 9,000 times longer

9. Trip to Proxima Centauri

   Quantity	Value
   distance	4.02 × 10¹³ km
   speed	17 km/s
   one year	3.16 × 10⁷ s

10. 8.

    A spacecraft at 17 km/s heads for Proxima Centauri, 4.02 × 10¹³ km away. About how many years would it take (1 year ≈ 3.16 × 10⁷ s), by Tala's math?

    • About 2.4 × 10¹² years
    • About 75,000 years
    • About 750 years
    • About 4.25 years
11. 9.

    1 parsec ≈ 3.26 light-years; distance 10 parsecs. A star is 10 parsecs away. About how long does its light take to reach Ari?

    • About 33 years
    • No time; it arrives at once
    • About 3.1 years
    • About 10 years
12. 10.

    About how many AU make 1 parsec, and why, by Bo's reading?

    • 1 AU, by definition
    • About 206,265 AU, where 1 AU spans 1 arcsecond
    • About 3.26 AU
    • About 63,241 AU