2020 chief astrophysicist Tasnim Ananna from Bangladesh explains exactly why black holes are so cool

Bangladeshi astrophysicist Tonima Tasnim Ananna, who recently surpassed the 2020 issue of Science News (SN) SN 10: Scientists to Watch, was praised for her outstanding pioneering research on black holes, including their origins and subsequent expansion along the time. Her research has mapped the size of black holes tracing its origins, location and its impact on its surroundings.

Baskuli reached out to Ananna to chat, hoping to understand the fascinating phenomena of black holes.

Toggle: How important are black holes in our understanding of the cosmos?

Ananna: Supermassive black holes living in the centers of galaxies are known to co-evolve with these galaxies. The energy bursts from the vicinity of these black holes can either cause star formation by disturbing neutral cold gas clouds that gravitationally collapse to form stars, or stop star formation if they inject too much energy into these clouds, causing them to evaporate. Therefore, understanding how galaxies evolve and what triggers or stops star formation, understanding how black holes evolve is most important.

However regardless of their roles in galactic evolution, supermassive black holes are some of the most mysterious objects we find in nature. It is still unclear how they form. Starbursts (such as Cygnus X-1) could be produced by falling stars, or by fusions of other dense objects such as neutron stars.

However, massive black holes, which are usually a million to a billion times larger than the sun, were to form very soon after the Big Bang. The Cosmic Microwave Background shows that after the Big Bang, matter was almost evenly distributed throughout the Universe, with very small perturbations. Over time, the small perturbations developed into superclusters of galaxies (where there was an overdensity of matter) or superoids (where there were sub-densities).

At the center of each massive galaxy, we find supermassive black holes, so the seeds of these black holes must form when matter first collapsed due to these perturbations – but the exact process that caused their formation is still unclear. To me, understanding how these objects formed and under what conditions they accumulated most of the thing to become so massive is interesting in itself.

Toggle: What can we say about the origins and expansion of black holes given the steps taken in research on them?

Ananna: We have a pretty good understanding of how supermassive black holes not wrapped in large amounts of gas and dust have evolved in the last 12 billion years. With upcoming missions like the James Webb Space Telescope observing the Universe in infrared wavelengths, we should have a clearer picture of earlier black holes.

The reason we need an infrared telescope to see further back in the Universe is because of the Doppler effect (quite simply, the faster an object moves away from us, the redder the light emitted by it appears relative to its stationary equivalent). As the Universe expands due to Dark Energy, galaxies move away from us. The farther away a galaxy is from us, the faster it moves away from us. Therefore, for the most distant galaxies / supermassive black holes, even all ultraviolet radiation passes to infrared wavelengths.

The black holes wrapped in gas and dust abound in the local Universe, but they are difficult to see in most wavelengths (such as visible light and ultraviolet) because these wavelengths are stopped by absorbing the surrounding clouds. In the last decade and a half, two orbital radiographic observatories have been launched – Swift-BAT and NuSTAR. X-rays can pass through these heavy clouds, ultimately giving us a glimpse into the surroundings surrounding these hidden black holes. These new data allow us to paint a complete picture of black hole growth.

Toggle: You and your team were able to look more clearly at the rotation of the black holes, an important feature. Could you delve deeper into how important this success is?

Ananna: The three fundamental characteristics of a black hole are its mass, load and spin. While mass can be directly calculated using star velocities around these black holes, the spin is more internal and must be derived from looking at the relationship between mass and light. Because our result is responsible for all the light emitted by supermassive black holes in the last twelve billion years, and we have measurements of black hole mass density in the current universe in literature, we can understand what the average backbone of these blacks is. holes. time passed.

Although previous models that did not account for much of the hidden / hidden AGN predicted that black holes are mostly stationary (i.e. Schwarzschild black holes), we find that rotating Kerr black holes are much more common than previously expected. The solution for general relativity, which describes a rotating black hole (found in the 1960s), is very different from that of a stationary black hole (found a year after general relativity was proposed by Einstein in 1915), and the way in which space curves around rotation. a black hole also differs (for example the disk of falling matter can move closer to the event horizon if the disk and the black hole both rotate in the same direction).

This is why spinal measurement brings us closer to understanding the surroundings around these black holes.

Toggle: What are the main challenges in your research and where do you plan to venture into the realm of black holes later?

Ananna: One major challenge in research is to balance quality versus quantity. There is always pressure to publish as much and as quickly as possible, although to produce valuable value it is best to take a step back and take your time. A few years ago a great article about it appeared, titled “Scientific knowledge drowns in a flood of research” – a series of comics in that article perfectly summarizes this issue that researchers are facing today.

About my current projects – now, I’m working with data from an X-ray observatory called Swift-BAT, which observes the universe with high-energy X-rays, but it only observes the local universe. Due to X-ray penetrating power, this will allow us to draw the most complete picture of how mass is distributed in local populations of black holes, update the mass density estimate that is still widely discussed, and quantify how much of the falling mass is radiated. away as light.

Toggle: What do you think are the main barriers in Bangladesh in researching such issues, and what are your recommendations for overcoming them?

Ananna: I think the main barrier in research is that our public institutions value relationships more than merit when it comes to recruitment. It’s hard to keep talent if it’s not valued. Another important aspect of research is funding.

Researchers in the United States regularly submit research projects to NASA and NSF (National Science Foundation), which are reviewed by peers, and the most meritorious projects are funded. All of my research projects have been funded by grants from NASA and NSF. In Bangladesh, at least in the sciences, I have not heard of anything like it. It is unlikely that a research environment will thrive if people cannot receive funding to collect data, hire graduate students and postdocs.

Illustration: Zarif Faiaz

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