Photon sphere

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/photon-sphere

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the location (schwarzschild black hole)?Approximately 1.5 times the Schwarzschild radius (Rs) from the singularity
2. What is the key feature?Innermost stable circular orbit (ISCO) for massless particles (photons)
3. Where is the photon sphere located around a non‑rotating black hole?For a non‑rotating black hole, the photon sphere is at 1.5 times the Schwarzschild radius, which is the size of the event horizon.
4. Why can light stay in a circular orbit at the photon sphere?The gravity bends light so tightly that it follows a closed path. If the light moves a little off that path, it will either fall into the black hole or fly away.

Geodesic: The shortest or longest path between two points in a curved space or spacetime.
Schwarzschild Radius: The radius of the event horizon of a non-rotating, uncharged black hole.
Accretion Disk: A structure formed by diffuse material in orbital motion around a massive central body, like a black hole.