Hard Questions at the Edge: teacher key

Black Holes, grade 10 edition, written for 10th grade. Black holes are measured by what they do to stars, light and space. Read how astronomers did it and what they still cannot explain.

Read the book. Print this page for the key.

Questions and answers

1. What does the size of M87's shadow rule out?
   • Exotic alternatives such as a wormhole (answer)
   • Einstein's theory
   • The need for any telescope
2. A black hole can double its mass about every million years, at most. About how much bigger could it grow in 10 million years?
   • About 10 times as big
   • About 1,000 times as big (answer)
   • About 10 million times as big
3. Which star helped show that a black hole is at the center of our galaxy?
   • Sirius
   • A white dwarf
   • S2 (answer)
4. How long does the Event Horizon Telescope need to observe Sagittarius A*?
   • Many hours (answer)
   • A few seconds
   • Exactly one minute
5. What does exotic mean in "exotic alternatives"?
   • Very old
   • Unusual (answer)
   • Very small

Words

• singularity: center point
• exotic: unusual
• accretion: falling together
• exposure: long look
• wormhole: space tunnel