Researchers’ bio

I am Tuomas Savolainen, a senior scientist at the Aalto University Metsähovi Radio Observatory and at the Department of Electronics and Nanoengineering.

I participated in the imaging of the data – that is, turning the interferometric measurements from the telescopes into an image. This was a non-trivial process since we have only a handful of telescopes and our data are incomplete. We had to use advanced algorithms to fill the gaps. The rapid variability of Sagittarius A* also made this harder than imaging the black hole in M87.  I was involved in finding solutions to these problems.  

What do pictures of black holes mean to you and your work?
The 2019 image of the black hole in M87 was a dream come true and the most memorable moment of my career. That image gave direct visual proof of the existence of supermassive black holes and confirmed that they indeed are the central engines powering so-called active galaxies. The significance of the Sagittarius A* image, in my opinion, lies in the fact that we know its mass and distance very accurately. This is thanks to astronomers who have spent decades measuring the motions of stars that orbit Sagittarius A*. When the mass and distance are precisely known, we can accurately calculate the gravitational effects around the black hole and then compare those predictions to the image taken by the EHT. ' The current EHT image of Sagittarius A* agrees with the General Relativity at a 10% level. Testing General Relativity in such a gravitational field and such a mass wasn’t possible before. When combined with the EHT image of the much more massive black hole in M87*, the results are in beautiful agreement with the predictions of the General Relativity, which says that the properties of the black hole space-time scale with the black hole mass. As the EHT images are expected become sharper in the future, the tests will also become tighter.

I am Postdoctoral Researcher Venkatessh Ramakrishnan, working at both the Finnish Centre for Astronomy with ESO and Aalto University’s Metsähovi Radio Observatory.

My primary contributions to this research was dealing with observations of the object from the APEX telescope in Atacama, Chile, processing the raw data and imaging them. I was also involved in the theoretical interpretation of the image in terms of the physics related to plasma flows under the theory of General Relativity.

The Atacama Pathfinder Experiment (APEX) is one of the submillimetre telescopes in Chile that is administered by the European Southern Observatory (ESO). APEX is one of the many telescopes that form the EHT network, and it has contributed to EHT’s work on M87*. As a member of the EHT APEX team since 2017, I carry out observations and also contribute to the technical duties that are vital to the functioning of the telescope during EHT observations. It is a great joy to see the data I collected being transformed into a final image after years of hard work, just like a seed transforming into a tree.

What do pictures of black holes mean to you and your work?
Pictures of black holes are fundamental for improving our understanding of how galaxies form and evolve. They are the best laboratory to test the theory of General Relativity. The image of SgrA* is certainly unique, since it completes a missing puzzle of the building blocks of our galaxy. By continuing to monitor SgrA* in the years to come, will help us to improve our understanding of how the supermassive black hole and our galaxy will co-evolve. With the images of SgrA* and M87*, we now have two images of black holes, but that merely scratches the surface of long-standing research connected to General Relativity. EHT will be an excellent tool to make images of other black holes in galactic centres, though this will require several technological improvements to its infrastructure. I will make extensive use of EHT as I lead a study of black holes in nearby galaxies. I hope to image at least about 5 other black holes within the next decade.

I am Senior Research Fellow Kaj Wiik from Tuorla Observatory, Department of Physics and Astronomy, University of Turku.

I participated in the data calibration and verification, imaging and the calibration of the physical parameters of Sgr A*.

What do pictures of black holes mean to you and your work?
The first image of the shadow of the black hole in the centre of our own galaxy is, of course, historic as an observation. Previously, the existence of the black hole could be inferred using indirect methods, but now we can image it and follow its rather rapid variability. Now that observing methods have been developed that enable varying black holes to be monitored, this improves our ability to test theories of general relativity and black holes.