Observing Black Holes

Explore 24.6 Evidence for Black Holes to examine the characteristics of binary star systems providing evidence for stellar-mass black holes and the presence of supermassive black holes in galactic centers.
In our “Compact Objects” lesson, we learned that astronomers were able to capture the first direct image of a black hole’s accretion disk in 2019. Here’s the news clip that I shared with you in that lesson: First Image of a Black Hole. The reality is that astronomers have been collecting lots of evidence for the existence of black holes for many years, even well before that image was captured. In fact, for decades there has been no doubt among astronomers that black holes truly exist. As material falls into a black hole, it forms an accretion disk, which becomes so hot that it glows in x-ray light. While this light does not come from inside the black hole (nothing can escape the black hole, right?), the only way to explain the tremendous energy in such a small area is, in fact, the gravitational energy provided by a black hole. Watch this brief video from NASA, which shows an example of this kind of black hole discovery from 2012.
Even images from the Hubble Space Telescope (like this photo of jets emerging from the core of the galaxy M87) had long ago convinced astronomers that there are supermassive black holes in the centers of most galaxies.
Today, we have numerous independent observations that provide evidence of black holes. Read 24.7 Gravitational Wave Astronomy to understand how gravitational waves, predicted by general relativity, were first detected by LIGO in 2015, marking a significant advancement in our ability to observe the universe.
Watch the video The Journey of a Gravitational Wave to learn more about the LIGO Detectors and their observations of the gravitational waves from merging black holes.
We know black holes exist, but they are just so insanely weird. Watch the Kurzgesagt video What If You Fall into a Black Hole to see a few of the strange properties of black holes as well as the limits of our understanding.