Galaxies, the Milky Way and our place in it

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   The Milky Way (NASA)

   Fact	Value
   disk width	more than 100,000 light-years
   Sun's distance from center	about 26,000 light-years (sources give 25,000 to 28,000)
   one orbit of the Sun	about 230 to 250 million years (sources differ)
   Andromeda	2.5 million light-years away

2. 1.

   About how many Milky Way widths away is Andromeda, by Bo's math?

   • About 2.5
   • About 250,000
   • About 25
   • About 2,500,000
3. 2.

   The Sun is about 26,000 light-years from the center (sources give 25,000 to 28,000). About what fraction of the disk's radius is that, if the radius is about 50,000 light-years, by Esme's math?

   • About half
   • About twice the radius
   • Zero, since the Sun is at the center
   • About one-tenth

4. Spiral galaxy speeds (model data)

   Distance from center	Measured speed	Speed from visible matter
   10,000 light-years	220 km/s	210 km/s
   30,000 light-years	220 km/s	150 km/s
   60,000 light-years	220 km/s	100 km/s

5. 3.

   Measured star speeds in a spiral galaxy stay near 220 km/s far from the center, but visible matter predicts they should fall. What does this suggest, by Kira's reading?

   • The outer stars are about to fly away from the galaxy soon
   • There is extra unseen mass holding the outer stars
   • The galaxy is made of dark dust
   • The speeds were measured in the wrong units
6. 4.

   In the same table, by how much does the measured speed beat the visible-matter speed at 60,000 light-years, by Luz's math?

   • By 10 km/s, as at the center
   • By 120 km/s
   • By 0 km/s; they match
   • By 320 km/s
7. 5.

   Vera Rubin studied stars at the outer edges of spiral galaxies in the 1970s (NASA). What did Rubin find, by Milo's reading?

   • Spiral galaxies are really ellipticals
   • Outer stars moved too fast for the visible matter alone
   • The galaxies had no outer stars
   • Outer stars moved slower than expected
8. 6.

   Why can't we photograph the whole Milky Way from outside, by Noah's reading (NASA)?

   • It is an elliptical with no disk
   • We are inside it, seeing the disk edge-on
   • We sit at its center
   • It is smaller than the solar system
9. 7.

   The two galaxies drawing together over billions of years. NASA says the Milky Way and Andromeda will meet in about 4 billion years. What does NASA say will happen to Earth, by Ren's reading?

   • It will happen within our lifetimes
   • Earth will be hit by Andromeda's stars
   • The Sun will move to the galaxy's exact center
   • The solar system is in no danger; the Sun may shift its place
10. 8.

    Sketch of a galaxy with a central bar and two main arms. Which galaxy type does NASA say the Milky Way is, by Tala's reading?

    • A ring of planets
    • A barred spiral
    • An irregular
    • An elliptical
11. 9.

    A galaxy is 10 million light-years away. Which statement is true, by Zee's reading?

    • We see it as it was about 10 million years ago
    • We see it as it is tonight
    • It is 10 million km away
    • It takes 10 million years for us to blink at it
12. 10.

    Pie chart of 30 nearby large galaxies with slices unlabeled. NASA says elliptical galaxies are less common than spirals. In a sample of 30 large galaxies, which count is most likely, by Ari's reading?

    • Equal numbers of each type
    • More ellipticals than spirals
    • Each of the 30 is irregular
    • More spirals than ellipticals