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?

   • They formed at one distance
   • Ice giant, gas giant, terrestrial
   • Terrestrial, gas giant, ice giant
   • Gas giant, terrestrial, 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)?

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

   • 20%
   • 2%
   • 99.8%
   • 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 swallowed the rocky planets
   • The cold outer disk had extra ice and gas to gather
   • They formed long after the Sun had cleared the gas away
   • They formed near the hot Sun
5. 5.

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

   • A planet exploded and scattered it
   • It is still there between the planets
   • The young Sun's early solar wind
   • Earth's gravity slowly pulled the gas in
6. 6.

   Planets build up; cloud collapses; solar wind clears the gas; Sun and spinning disk form. Which order matches the formation steps, by Milo's reading?

   • Gas is cleared first, then the cloud collapses
   • Planets build, cloud collapses, Sun forms, gas is cleared
   • Sun forms, then the cloud collapses around it
   • Cloud collapses, Sun and disk form, planets build, gas is cleared

7. Read this first

   Density (NASA Planetary Fact Sheet)

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

8. 7.

   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
   • Saturn is mostly gas; Earth is mostly rock and metal
   • Both are made of the same things
   • Saturn is mostly rock and metal; Earth is mostly gas and ice
9. 8.

   Asteroids are about 4.6 billion years old (NASA). Why do scientists study them to learn about the solar system's start, by Pia's reading?

   • They are older than the universe
   • They are pieces of a broken planet
   • They formed just a few thousand years ago
   • They are leftovers that have changed little since the start
10. 9.

    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 9.2 million years
    • It formed at the same moment
    • About 9.2 billion years
    • About 18.4 billion years
11. 10.

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

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