Issued on: 22/05/2022 – 09:26
On May 12, scientists from an international research team called the Event Horizon Telescope (EHT) Collaboration discovered the first image of Sagittarius A *, the supermassive black hole at the center of our Milky Way galaxy.
This is the result of observations made using a global set of radio telescopes that form EHT.
Dr. Frederick Gett, deputy director of the Grenoble-based Institut de Radioastronomie Millimetrique (IRAM), is one of the scientists involved in the project.
In an interview with RFI’s Dhananjay Khadilkar, Gueth spoke about the monumental efforts to capture this image and its significance.
Q1. What is a black hole and why is it at the center of our galaxy?
The black hole is one of those fascinating objects whose presence was predicted by Albert Einstein. It is so massive that nothing, not even light, can escape it.
We can’t see a black hole because nothing can come out of it. However, there is a trick to complying with it. There is a black hole in the center of every galaxy, not just the Milky Way.
Sagittarius A * is four million times more massive than the Sun, which is already an incredibly massive object. It is 27,000 light-years away.
Q2. How did you capture the image of Sagittarius A *?
We knew there was a black hole (in the center of our galaxy), but we never had a direct image of it.
All the evidence we had of its existence was circumstantial. To observe the black hole, we used a network of radio telescopes that operate in the millimeter (wavelength) domain.
We have 10 observatories around the world. All observations from different locations were performed simultaneously. We had to have atomic clocks on all these sites to make sure the synchronization was perfect.
The data (observations) were combined using a very complex mathematical process to create this non-optical image.
We had to watch for radio wavelengths for one simple reason. There is a lot of gas and dust in the interstellar medium that absorbs light with an optical wavelength. Therefore, we cannot observe the vicinity of the black hole in the optical wavelength.
Q3. Of the ten telescopes that form the EHT array, two belong to IRAM. What are the characteristics of these two telescopes?
One is a 30-meter-diameter antenna located in the Sierra Nevada in Spain. The other instrument, called NOEMA or Northern Extended Millimeter Array, is an array of 12 antennas, each 15 meters in diameter. Located in the French Alps. These two tools are extremely sensitive.
Q4. Three years ago, EHT Collaboration shot the first image of a black hole. Why is it important to capture images of black holes?
(Until these images were made), all the evidence we had of the existence of black holes was circumstantial. We observed the orbits of stars around black holes. Calculating the speed of the stars, we will conclude that the mass of the central object must be so large that it must be a black hole.
We have never had direct images of black holes. It is therefore extremely satisfactory to make these observations so that we really know that it exists. In addition, we can begin to study the physics of the material around black holes.
Add Comment