Astronomical units, light-years and parallax

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Distance from the Sun (NASA Planetary Fact Sheet)

   Planet	Distance (million km)
   Earth	149.6
   Jupiter	778.5

2. 1.

   Jupiter is about 778.5 million km from the Sun (NASA). About how many AU is that, using 1 AU ≈ 149.6 million km, by Bo's math?

   • About 116,000 AU
   • About 0.19 AU
   • About 5.2 AU
   • About 5.2 light-years
3. 2.

   Note: light speed 299,792 km/s. Neptune is about 4,515 million km from the Sun (NASA). About how long does sunlight take to reach it, at 299,792 km/s, by Esme's math?

   • About 4.2 minutes
   • About 4.2 hours
   • About 4.2 years
   • About 15 minutes
4. 3.

   Distance (parsecs) = 1 ÷ parallax (arcseconds); 1 parsec ≈ 3.26 light-years; parallax 0.10. A star's parallax is 0.10 arcseconds. How far away is it, by Kira's math?

   • 100 parsecs, since a small shift means near
   • 0.1 parsecs
   • 10 parsecs, about 33 light-years
   • 10 light-years
5. 4.

   Distance (parsecs) = 1 ÷ parallax (arcseconds); parallax about 0.77. Proxima Centauri's parallax is about 0.77 arcseconds. About how far is it in parsecs, by Luz's math?

   • About 0.77 parsecs
   • About 1.3 light-years
   • About 77 parsecs
   • About 1.3 parsecs

6. Two parallaxes

   Star	Parallax (arcseconds)
   A	0.2
   B	0.05

7. 5.

   Star A's parallax is 0.2 arcseconds; star B's is 0.05. Which is nearer, and by what factor, by Milo's math?

   • A, 0.15 parsecs nearer
   • They are equally far
   • A, 4 times nearer
   • B, 4 times nearer
8. 6.

   Four distance cards, labeled A to D. Which distance is given in a sensible unit, by Noah's reading?

   • Sun to Proxima Centauri: about 268,770 parsecs
   • Sun to Saturn: about 9.6 AU
   • Earth to the Moon: about 2.6 light-years
   • Across the Milky Way: about 100,000 AU
9. 7.

   Why do astronomers give star distances in light-years instead of kilometers, by Pia's reading?

   • A light-year is smaller than a kilometer
   • Light-years tell how old stars are
   • Kilometer values for stars are enormous
   • Kilometers cannot be used off Earth
10. 8.

    9,460,000,000,000 km. How is 9,460,000,000,000 km (about 1 light-year) written in scientific notation, by Tala's reading?

    • 9.46 × 10¹² km
    • 94.6 × 10¹² km
    • 9.46 × 10¹⁵ km
    • 9.46 × 10⁹ km

11. Distances (NASA)

    Object	Distance (km)
    Sun	1.50 × 10⁸
    Proxima Centauri	4.02 × 10¹³

12. 9.

    Proxima Centauri is about 4.02 × 10¹³ km away; the Sun is about 1.50 × 10⁸ km away. About how many times farther is Proxima, by Zee's math?

    • About 5 times
    • About 2.7 × 10²¹ times
    • About 2.7 × 10⁵ times
    • About 6.0 × 10²¹ times
13. 10.

    c = 299,792,458 m/s (NIST); 1 year ≈ 3.156 × 10⁷ s. NIST gives light speed as 299,792,458 m/s; a year (365.25 days) is about 3.156 × 10⁷ s. About how many meters is a light-year, by Ari's math?

    • About 9.46 × 10¹⁵ m
    • About 9.46 × 10¹² m
    • About 9.46 × 10⁵⁶ m
    • About 9.5 m