Worlds Around Other Stars: teacher key

Aliens and UFOs, grade 8 edition, written for 8th grade. Scientists have confirmed more than 6,000 planets around other stars as of October 2026. Transits, wobbles and gravity tricks found them, and the search for life on them goes on.

Read the book. Print this page for the key.

Questions and answers

1. Why is direct imaging of exoplanets hard?
   • The planet is too close to Earth
   • The star's light overwhelms the planet (answer)
   • Planets give off too much light
2. What did the Kepler space telescope do?
   • Watched stars for transits and found planets (answer)
   • Landed on Mars
   • Listened for radio signals
3. What is the habitable zone?
   • The center of a star
   • The path of a comet
   • The area around a star where a planet could have liquid water (answer)
4. What did Kepler leave behind when NASA retired it in October 2018?
   • More than 2,600 planet discoveries (answer)
   • A landing site on Mars
   • A radio signal
5. According to AARO, why are many reports listed as unidentified?
   • They were proved to be spacecraft
   • Sensors could not collect enough information (answer)
   • No one reported them
6. What does the word wobble mean here?
   • A planet crossing a star
   • A rover tipping over
   • A star being tugged back and forth by a planet's gravity (answer)

Words

• exoplanet: far-off planet
• spectrum: light spread out
• microlensing: gravity magnifying light
• astrobiology: study of life
• unidentified: not yet named