Three years after the publication of the first-ever photograph of a black hole, astronomers from the Event Horizon Telescope (EHT) project have published a second such image. This time, scientists captured a supermassive black hole in the center of our own galaxy.
To begin with it is necessary to clarify that it is more correct to speak about a photo of the black hole’s shadow, as the object itself does not emit anything, so it is impossible to photograph it. Also it is necessary to remind that we are not talking about classical photography. The Event Horizon Telescope (EHT) is a combination of many radio telescopes all over the Earth, which results in a “virtual” telescope “the size of the Earth”.
Be that as it may, we can now estimate our home supermassive black hole. The object is located at the center of our galaxy, only about 27,000 light years away. The mass of our black hole is estimated at 4 million solar masses. By comparison, the black hole at the center of the Messier 87 (M 87) galaxy, whose photo appeared three years ago, has a mass of about 6.5 billion solar masses and is about 54 million light-years away. Despite the enormous difference in distance, the new photo looks about the same, if not a little worse.
The point is that Sagittarius A*, the common name for the object at the center of our galaxy, is much more volatile than its larger counterpart by orders of magnitude. Data on both black holes were collected simultaneously: during five nights in 2017. But it took three years longer to process information about our object, as we can see. If the black hole in the center of M 87 because of its size practically did not change during the whole time of observations (we are talking about changes in clots of matter around the hole), then Sagittarius A* changed during every 5-15 minutes. Because of this, scientists had to take thousands of photos, and the one we see today is an average image.
The current image is also important because previously there were various theories that there was no supermassive black hole in the center of our galaxy. But now we can confidently say that there is one.
The EHT system consisted of eight telescopes at the time of the data in 2017. Now there are 11, and astronomers have already used the addition to obtain new data, so that later we may see a clearer image of our black hole.