Astronomical units, light-years and parallax

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   What is 1 astronomical unit (AU), by Ari's reading (IAU)?

   • The Earth-Sun distance, about 150 million km
   • The width of the Milky Way
   • The distance light travels in a year
   • The time light takes to leave the Sun
2. 2.

   not to scale. Which unit best fits the distance to a nearby star, by Kira's reading?

   • Light-years or parsecs
   • Years
   • Astronomical units, since stars are close
   • Kilometers per hour

3. Read this first

   Parallax diagram

   Earth at two sides of its orbit, a near star and a far star, with sight lines to a distant background.

4. 3.

   Two stars are photographed six months apart against far background stars. Which shows the larger parallax shift, by Jun's reading?

   • The brighter star
   • The farther star
   • Both shift the same
   • The nearer star
5. 4.

   Astronomers mark a star's place, then mark it again from the other side of Earth's orbit. How much later is that, by Luz's reading (NASA)?

   • One hour later, the same night
   • Twelve months later, from the same spot
   • Six months later, when the farthest stars shift most
   • Six months later
6. 5.

   Distance (parsecs) = 1 ÷ parallax (arcseconds); parallax 0.5. A star's parallax is 0.5 arcseconds. How far away is it in parsecs, by Milo's math?

   • 0.2 parsecs
   • 50 parsecs
   • 0.5 parsecs
   • 2 parsecs
7. 6.

   About how many kilometers is 3 AU, using 1 AU ≈ 150 million km, by Noah's math?

   • About 450 billion km
   • About 450 million km
   • About 50 million km
   • About 3 light-years
8. 7.

   1 parsec ≈ 3.26 light-years; Proxima Centauri about 4.25 light-years. Proxima Centauri is about 4.25 light-years away (NASA). About how many parsecs is that, by Ren's math?

   • About 13.9 parsecs
   • About 1.3 parsecs
   • About 0.77 parsecs
   • About 4.25 parsecs
9. 8.

   Light takes how long to cross 1 AU, from the Sun to Earth, by Tala's reading?

   • No time; light arrives at once
   • About 1 year
   • About 8.3 hours
   • About 8.3 minutes
10. 9.

    Light from Proxima Centauri (4.25 light-years away) reaches Zee tonight. When did it leave the star?

    • Tonight, at the moment it is seen
    • About 4,250 years ago
    • About 4.25 minutes ago
    • About 4.25 years ago
11. 10.

    Light-year, year, light-minute. Which of these are distances: a light-year, a year, a light-minute, by Esme's reading?

    • A light-year and a light-minute
    • A light-year, but not a light-minute
    • They are times, not distances
    • Just the year