Why is the black hole image so fuzzy? Do black holes really look like lopsided donuts? Why does this matter? Everyday Einstein, Dr. Sabrina Stierwalt, explains the significance of this monumental scientific achievement.
Some of the photons in that sphere are moving toward us observers sitting here on Earth in their trip around the black hole while others move away from us. The portion of the light moving towards us appears brighter thanks to the Doppler effect. (This is a similar effect to that which causes an ambulance siren to change pitch as it moves toward you versus away from you.)
As described by Harvard scientist Shep Doeleman, the project director for the team that made the image, “Nature has conspired to let us see something we thought was invisible.” Excitingly, this lopsided donut shape is predicted by Einstein’s theory of general relativity.
How big is this black hole?
The supermassive black hole weighs as much as 6.5 billion suns and lies at the heart of the giant elliptical galaxy Messier 87. Messier 87 is the most massive galaxy in the nearby Virgo Cluster and contains somewhere on the order of several trillion stars. For comparison, the Milky Way is home to a few hundred billion stars.
Astronomers can calculate the mass of the black hole thanks to studying the orbiting material, but determining the size is a bit more challenging since we don’t know how fast the black hole is spinning or its precise orientation relative to our view. We expect, however, that our entire solar system would fit within the central dark smudge and that the darkness may extend more than 120 times the distance from us here on Earth to the Sun.
Our entire solar system would fit within the central dark smudge and the darkness may extend more than 120 times the distance from us here on Earth to the Sun.
Why is the image so fuzzy?
With the release of the image, I saw more than one (very funny) internet meme poking fun at how excited astronomers were over such a blurry image. Messier 87’s black hole is certainly large, but being large is only part of what makes getting a clear image possible. That object also has to be nearby. Katie Bouman, a professor at Caltech and the lead developer of the algorithm used to create the image, described just how hard it is—and thus how impressive—to get an image of this particular black hole. She said, “It’s about the same size as if you were trying to take a picture of an orange on the moon.”
Why didn’t we image the black hole in our own galaxy?
So if proximity is key, why didn’t the Event Horizon team instead image the supermassive black hole known to reside in the center of our own galaxy? Well, they did image our own supermassive black hole, known as Sagittarius A*, and plan to release that data as well. However, we should expect the quality of the image to be roughly the same because what we gain in proximity from Sagittarius A*, we lose in size relative to Messier 87’s black hole. Our own black hole neighbor weighs in at only about 4 million suns so although it is nearly two thousand times closer than Messier 87, it is on the order of two thousand times smaller.
For more on how these ground breaking observations work, you can check out Dr. Bouman’s TED talk.
Until next time, this is Dr. Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at firstname.lastname@example.org.
Image courtesy of the Event Horizon Telescope Collaboration.