Black hole (noun, “BLAAHK HOAL”)
This is a spot in space that has a powerful gravitational pull. A black hole’s gravity is so strong that not even light can escape.
Black holes aren’t actually holes. They are objects that contain a lot of mass packed into a tiny area. Most black holes form when giant stars die and collapse. As a star dies, the material it’s made of gets squeezed into a smaller and smaller space. Eventually it forms what’s called a stellar mass black hole. Astronomers estimate that one of these relatively small black holes is born every second. Supermassive black holes are much bigger, as their name suggests. Instead of containing the mass of one star, they can contain the mass of millions or billions of stars. Scientists aren’t quite sure how those behemoths form.
Scientists first picked up hints about black holes in the late 1700s. But no one had actually seen one until recently. Because light can’t leave a black hole, it’s not possible to see one with a regular telescope. But many black holes are surrounded by a swirling ring of gas and other material. This ring, called an accretion disk, heats up and emits light. Scientists can study that light to learn about black holes.
In early 2019, scientists shared the first picture of a black hole. They made this image using a virtual telescope that combined the powers of eight observatories around the world. With this virtual telescope, the team of scientists zoomed in on the shadow the black hole cast on its glowing accretion disk.
In a sentence
The Milky Way, Earth’s home galaxy, may hold 100 million black holes.