By Parshati Patel, PhD
What are black holes?
Imagine squeezing a really big star into a small area, like the size of the Moon! This is what happens when a black hole forms. It is a region of space where so much matter is packed into a tiny area that its gravity becomes incredibly strong. Gravity is a force that pulls things together. In a black hole, gravity is so strong that nothing, not even light, can escape! This is why the black hole looks completely black.
The edge of the black hole is called the event horizon. It’s like an invisible boundary. Even though we cannot see the black hole itself, we can spot it by looking at the material around it. As this material gets closer to the event horizon, it travels at high speeds, and it heats up and glows! We can detect this glow using telescopes.
How do black holes form?
Black holes come in different sizes, and while we know how some types form, others remain a mystery. There are three main types of black holes, categorized by their mass and size: stellar-mass black holes, intermediate-mass black holes, and supermassive black holes.
Stellar-Mass Black Holes
Intermediate-Mass Black Holes
Supermassive Black Holes
Are black holes the vacuum cleaners of the universe?
Black holes don’t ‘suck’ in matter unless it gets very close to them. If our sun were replaced with a black hole of the same mass, Earth wouldn’t get sucked in. The planets would continue to orbit the black hole like they do around the Sun now. The only difference we would experience would be the loss of the Sun’s warmth and light, leaving the Solar System dark and cold.
What happens if you travel to a black hole?
Imagine you are on a journey to a black hole in a spacecraft. As you approach the event horizon, you suit up and step out of the spacecraft. As you move closer to the black hole feet first, something strange happens: the gravity near your feet is much stronger than the gravity near your head! The intense difference in gravitational pull stretches your body vertically while squeezing it horizontally, like a spaghetti noodle! Astronomers call this process spaghettification.
Did you know…
A supermassive black hole – known as Sagittarius A * (Sgr A*) – is at the centre of our Milky Way galaxy. It has a mass of 4 million Suns! Using the Event Horizon Telescope, astronomers captured the first-ever image (see below) of the Sagittarius A* – in 2022.
Dr. Parshati Patel is an astrophysicist turned freelance science communicator and educator based in London, Ontario.
