Black Holes
Black holes are regions where gravity is so strong that light can't escape.
About this topic
A black hole is a region of space where gravity is so strong that nothing, not even light, can escape beyond its event horizon. Stellar black holes form when massive stars collapse after a supernova; supermassive ones with millions or billions of solar masses lie in galactic centres, including Sagittarius A* in our galaxy.
We detect black holes by their effects on nearby stars, X-rays from heated infalling matter, gravitational waves from mergers, and, in 2019, the first image of one (M87*). Falling in would stretch you ("spaghettification").
To appreciate the scale, the Schwarzschild radius gives the size of the event horizon: for a black hole of the Sun's mass it would be only about 3 km, and for Earth's mass about 9 mm. Sagittarius A* has about 4 million solar masses, and astronomers measured it by tracking stars that orbit it at thousands of km per second, work that earned the 2020 Nobel Prize. The first gravitational waves, detected in 2015 by LIGO, came from two black holes merging about 1.3 billion light-years away.
Black holes matter as laboratories for gravity at its extreme and because supermassive ones influence how galaxies grow. A black hole does not suck in everything; if the Sun were replaced by one of equal mass, Earth would keep orbiting normally, just in the dark. A common misconception is that black holes are cosmic vacuum cleaners or physical holes; they are extremely dense objects. The bright glow near them comes from matter in the accretion disc, not from the black hole itself, and Hawking showed that they can slowly lose energy through radiation.
Key ideas
- Event horizon
- Form from collapsed stars
- Detected by effects on nearby matter
Quick check
Use cases: where Black Holes helps
- Homework: review the key idea behind Black Holes before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Black Holes without notes.
- Visual learning: play with the interactive lab to see how Black Holes changes when you adjust its inputs.
- Teaching a friend: explain Black Holes in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is Black Holes?
Black holes are regions where gravity is so strong that light can't escape.
What will I learn in Black Holes?
Event horizon. Form from collapsed stars. Detected by effects on nearby matter.
Is Black Holes part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Black Holes lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Black Holes?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.