We see a black hole’s photon ring for the first time (PICTURES)
On the edge of science fiction
The first photo of a black hole was first captured by the Event Horizon Telescope in 2019, and if you remember, it wasn’t a very impressive image as it looked like a fuzzy orange doughnut. The hidden treasure of the image was in the data we extracted and not in the image itself.
Black holes naturally do not emit light themselves. The light we see is not from the plasma jets or superheated gases around the hole either. Instead, it comes from photons which, when they pass close by the black hole, drastically change direction due to the distortion of space-time.
The so-called photon ring is the location where gravity is so strong that light travels in a perpetual circle. Photons orbit the black hole in this region. If we were there, a photon would leave the back of your head, circle the black hole, and be seen by your eye – you would practically see the back of your head. Of course you would be dead due to gravity but you understand how it works.
The size of the photon ring depends on the mass of the black hole, and its brightness depends on its rotation rate. So why didn’t the EHT image show us the photon ring directly? Unfortunately for us, the space between the black hole and Earth is not empty. There is a region of cold gas that the light must pass through to reach us, causing it to scatter along the way, blurring the image.
Scientists removed the glare from the image using algorithms. revealing two images that were hidden in the EHT data. One is the photon ring itself and the other is the glow of the surrounding area. This way we can also discover the gases that surround the black hole.
The new research is a very good example of analyzing data in innovative ways. Modern astronomical observations with powerful instruments gather such a quantity of data that many times it is more than we expect. As we learn how to process this data, we can uncover observations that were not made in earlier records.
The research was published in The Astrophysical Journal .
