How the solar system formed

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   Disk with a hot inner zone and a cold outer zone. Sort these by where they formed, nearest the Sun first: an ice giant, a terrestrial planet, a gas giant. By Bo's reading, which order fits?

   • Ice giant, gas giant, terrestrial
   • They formed at one distance
   • Gas giant, terrestrial, ice giant
   • Terrestrial, gas giant, ice giant
2. 2.

   Disk with a line marked where ice could survive. Water ice could survive in the young disk only far enough from the Sun. What did that allow out there, by Esme's reading (NASA)?

   • Rocky planets grew bigger than Earth in the cold outer disk
   • The Sun formed there
   • Nothing could form beyond the line
   • Ices and gases gathered into the giant planets
3. 3.

   NASA says the Sun holds 99.8% of the solar system's mass. What share is left for everything else, by Jun's math?

   • 2%
   • 99.8%
   • 20%
   • 0.2%
4. 4.

   Disk with a cold outer zone rich in ice and gas. Jupiter has about 318 times Earth's mass (NASA). Why could the giants grow so big, by Kira's reading?

   • They formed near the hot Sun
   • The cold outer disk had extra ice and gas to gather
   • They formed long after the Sun had cleared the gas away
   • They swallowed the rocky planets
5. 5.

   What cleared the leftover gas and dust from the young solar system, by Luz's reading (NASA)?

   • Earth's gravity slowly pulled the gas in
   • A planet exploded and scattered it
   • It is still there between the planets
   • The young Sun's early solar wind

6. Read this first

   Density (NASA Planetary Fact Sheet)

   Planet	Density (kg/m³)
   Earth	5,514
   Saturn	687

7. 6.

   Saturn's density is 687 kg/m³ and Earth's is 5,514 kg/m³ (NASA). What does this fit, by Noah's reading?

   • Earth is mostly gas
   • Both are made of the same things
   • Saturn is mostly rock and metal; Earth is mostly gas and ice
   • Saturn is mostly gas; Earth is mostly rock and metal
8. 7.

   The universe is about 13.8 billion years old and the solar system about 4.6 billion. For about how long had the universe existed when the solar system formed, by Ren's math?

   • About 18.4 billion years
   • About 9.2 million years
   • It formed at the same moment
   • About 9.2 billion years
9. 8.

   NASA says a nearby exploding star's shockwave may have started the cloud's collapse. What does that suggest, by Tala's reading?

   • The cloud did not collapse
   • The planets came from that exploding star itself
   • The solar system is the oldest thing in the universe
   • Earlier stars existed and added material to the cloud
10. 9.

    Most planets also spin on their axes in the same direction they orbit. Why does that fit the formation story, by Zee's reading?

    • The cloud did not spin
    • The planets spin because they are cooling
    • They kept the spin of the disk they formed in
    • Each planet was captured separately
11. 10.

    Which statement about the asteroid belt matches NASA, by Ari's reading?

    • Rocks blasted off Mars recently
    • Bits that never came together into a planet
    • The remains of a planet that broke apart
    • Gas that did not turn into rock, left between Mars and Jupiter