AstroTeach had the honor of speaking with Professor István Horváth on November 6, 2025, in a deeply insightful conversation exploring the mysteries of gamma-ray bursts, the structure of the Universe, and the frontiers of modern astrophysics and cosmology.

Professor Horváth is a distinguished astrophysicist best known for his pioneering research on gamma-ray bursts (GRBs) and the large-scale structure of the cosmos. His influential work on the classification of GRBs and the discovery of potential large-scale cosmic structures—including claims suggesting patterns beyond the expected uniformity of the Universe—sparked major scientific discussion and contributed to one of the most fascinating debates in contemporary cosmology.

He serves as a professor at the National University of Public Service (NUPS) in Budapest, Hungary, where he leads research and inspires the next generation of scientists. His publications have appeared in leading astrophysical journals, and his contributions have helped shape our understanding of some of the most energetic and distant phenomena in the Universe.

In our conversation, Professor Horváth reflects on his scientific journey, the challenge and excitement of studying the deep cosmos, the evolving landscape of cosmological discoveries, and his perspective on curiosity, scientific integrity, and the importance of open-minded inquiry in astrophysics.

We are grateful for his time and generosity in sharing his knowledge with the AstroTeach community.

Firstly, I would like to thank you for the kind invitation.

Secondly, I want to point it out that AI, artificial intelligence, became more and more important in everybody’s life. One cannot underestimate the importance of the AI in the following years. Therefore, I’ll come back the AI during the interview.

For demonstrate I will answer question 2 and 4 with an audio. One is recorded the other one is created by AI.

1. Could you please introduce yourself to our audience and share how your early experiences and education led you into physics and, eventually, astrophysics?

My name is Istvan Horvath. I am a physicist and an astronomer. I was born and raised in Debrecen, the second largest city in Hungary. As a child, I was fascinated by the night sky. 

I was 6 years old when the Moon landing happened. Many times in the playground we imagined there is a spaceship there and played that we are astronauts. Behind the iron curtain we didn't know Star Trek. But we had a German series Spaceship Orion. So, I dreamed of being an astronaut. But I thought let’s be an astronomer first. Or just an amateur astronomer.

As I said, I was fascinated by the night sky. I could only see the beautiful night sky just a several times a year, because from a city of 200,000 people, only the brighter stars were visible. But luckily my grandparents lived in a village and in the 70s the street lighting wasn't very bright. The backyard away from the street was excellent for observation.

Every September there was an astronomy week in the city. I listened to the lectures, then later I went to the astronomy club every week. One could borrow binoculars and a 6-centimeter telescope from the club. So, I admire the Milky Way and watched the deep-sky objects like globular clusters, galaxies and so on. I also observed variable stars and sent my observations to the Hungarian association and also to the AAVSO, the American Association of Variable Star Observers. However, during my university studies I had less time for observations, so I became a professional astronomer. But I still look for opportunities to watch the sky when I get to an area with less light pollution.

2, Have you had any teachers or mentors who inspired you, and what did you learn from them?

Many of my teachers taught me lot’s of thing, including humbleness. I remember when we studied calculus I said to my high school math teacher, János Mucsa, we are smarter than Galilei. He did not agree. Then I said we know more than Galilei. He did not agree. Finally, all I could say was; there is one thing which we know and Galilei did not.

Later, I have been very fortunate to learn from several remarkable scientists who shaped both my professional path and my way of thinking. During my University study two people stand out in particular: Professor Béla Lukács and Professor György Paál.

From Béla Lukács, who supervised my diploma and early research work, I learned the importance of rigor in theoretical physics and the beauty of Einstein’s general relativity.

György Paál, on the other hand, inspired me with his creative approach to cosmology. He had an exceptional ability to connect large-scale observations with theoretical models.

3, Could you tell us about some of the significant projects, discoveries, or scientific contributions you've been involved in?

I would like to stay a bit with my early years. In the early 90s we have lots of visitors in Budapest. One of them Nándor Balazs, from Stony Brook University which is in Long Island, was the last assistant of Einstein. He was a friend of Eugene Wigner the Hungarian Nobel laureate. Not only he had great ideas, He also told us lots of anecdotes about these famous physicists. He also worked with Schrödinger in Ireland.

In the early 90s I worked with Béla Lukács on Black Holes. Some years later with György Paál on Cosmology. That time also a Hungarian born Peter Mészáros visited our institute and was looking for help for gamma-ray bursts cosmology. So when I visited Nándor Balazs on Long Island Peter invited me to visit Penn State, too. A year later I spent a year at Penn State working on gamma-ray burst cosmology with Peter (Meszaros).

Before my visit, Zsolt Bagoly had spent 2 years in Penn State. Also another native Hungarian from Prague, Attila visited Peter twice. During my stay at Penn State Peter invited Lajos Balazs, the director of the Hungarian Konkoly Observatory to work with us. Therefore, Peter was the founder of our High Energy Astronomy Research Team (HEART). These 5 people were the core of our research group. The next 3 decades we published more than hundred scientific papers together, mostly on gamma-ray bursts and received several research grants.

4. You’re known for your groundbreaking research identifying a possible third class of GRBs in addition to the short and long types. Could you explain what led you to this conclusion and how the scientific community responded?

For a long time, gamma-ray bursts (GRBs) were believed to fall into two main categories: short and long bursts, primarily distinguished by their duration. However, as I was analyzing the large BATSE dataset from the Compton Gamma Ray Observatory in the late 90s, I noticed that the distribution of burst durations was not bimodal. Instead, there seemed to be an intermediate group — bursts lasting roughly between two and ten seconds — forming a distinct peak in the duration distribution.

To explore this, I performed, statistical tests whether two or three log-normal components best described the observed data. The results consistently favored three classes. This led to the hypothesis that a third type of gamma-ray burst might exist, possibly representing a different kind of progenitor or emission mechanism.

In the standard picture, short gamma-ray bursts are typically associated with the merger of two compact objects, such as neutron stars or a neutron star and a black hole. These cataclysmic events release enormous energy in a fraction of a second and, as we now know, also produce gravitational waves — a fact spectacularly confirmed by the joint detection of GW170817 and its gamma-ray burst counterpart.

Long GRBs, by contrast, are believed to result from the collapse of massive stars, so-called collapsar or hypernova, where a newly formed black hole drives powerful relativistic jets through the dying star’s envelope.

The intermediate gamma-ray bursts — the third class we proposed — remain a subject of debate, but several models have been suggested. Some researchers argue that they may come from magnetar-powered explosions, partially failed jets, or mergers occurring in dense stellar environments, where the duration and spectral characteristics fall between the canonical short and long populations. Understanding these progenitors is essential, because they connect gamma-ray bursts not only to stellar evolution but also to the formation of black holes and neutron stars — the “endpoints” of stellar life.

The intermediate class idea initially sparked some debate, as it challenged the traditional two-class paradigm that had been widely accepted. However, over time, independent studies using data from other satellites also found evidence supporting this third, intermediate class. Today, while the physical interpretation is still discussed, the statistical reality of a three-group structure is recognized in the literature.

5. What are some of the most surprising or puzzling patterns you’ve found in GRB behavior over your career?

One puzzling pattern is the anisotropy that sometimes appears in the angular distribution of GRBs when large datasets are examined. Although the overall distribution is isotropic, subtle clustering effects may hint at underlying cosmic structures or selection biases.

In our first work on this we also found the GRBs sky distribution isotropic. Lajos Balázs was who pointed out, that although the short GRBs’ sky distribution showed no deviation from the isotropic distribution, so as the long ones, to compare the short and long GRBs distribution the two burst populations sky distribution statistically differ from each other.

This is how we started to analyzing the angular distribution of the GRBs.

6. One of your most discussed findings relates to evidence of very large structures — like the Hercules–Corona Borealis Great Wall — that challenge the assumption of cosmic uniformity. What do these structures mean for our understanding of cosmology?

Indeed, the discovery of the Hercules–Corona Borealis Great Wall is one of the most intriguing outcomes of gamma-ray burst studies. More than a decade ago we started to work with professor Jon Hakkila, who now is an Associate provost at University of Alabama in Huntsville. Around 2013, our analysis of GRB spatial distributions revealed an unexpected clustering of bursts in a particular region of the sky, corresponding to redshifts around 2. When interpreted cosmologically, this cluster appeared to trace a structure spanning nearly 10 billion light-years — making it one of the largest known features in the observable Universe.

What makes this so fascinating is that such a size seems to exceed the limits predicted by the cosmological principle, which assumes that the Universe is homogeneous and isotropic on sufficiently large scales. The Great Wall does not necessarily invalidate that principle, but it invites us to refine it — perhaps the transition to large-scale uniformity happens at greater distances than we previously thought, or maybe GRBs trace a particular type of matter distribution not perfectly aligned with galaxies.

The scientific community’s response has been mixed but constructive. Some colleagues are cautious, suggesting that the pattern might result from selection effects or incomplete sampling, while others have found supporting hints in quasar and galaxy surveys. What is clear, however, is that GRBs have proven to be a valuable new cosmological probe, capable of revealing structures that traditional surveys might miss.

For me, the deeper message is that the Universe still holds surprises at every scale. These immense structures remind us that even our most established cosmological assumptions must continually be tested against observation.

7. How do you differentiate between true cosmic patterns and observational biases from the instruments we use?

That is one of the most fundamental challenges in observational astrophysics — and especially in gamma-ray burst research. GRBs are detected by a variety of instruments, each with its own sensitivity, energy range, and sky coverage, which inevitably introduce biases. Distinguishing real cosmic structures from instrumental artifacts therefore requires both statistical rigor and caution.

In my work, I always begin by testing the robustness of a pattern using multiple, independent datasets — for example, comparing BATSE results with those from Swift or Fermi. If a structure or correlation persists across instruments with different selection functions, that increases our confidence that it reflects a real astrophysical phenomenon rather than an observational artifact.

We also perform Monte Carlo simulations to model how a truly random, isotropic distribution of bursts would appear given each detector’s limitations. By comparing those synthetic distributions to the observed data, we can quantify how likely it is that a given pattern arises purely from selection effects.

Another important step is blind statistical testing — analyzing the data without prior assumptions about where a structure “should” appear. This minimizes subconscious bias and helps ensure that our conclusions are data-driven.

Ultimately, it’s a balance between skepticism and curiosity. We must be open to unexpected patterns — like the possible large-scale structures we’ve discussed — while maintaining a critical awareness that our instruments, and even our methods, shape what we see. True progress in astrophysics often comes from understanding both the Universe and the tools through which we observe it.

8. How have missions like BATSE, Swift, and Fermi changed the landscape for GRB research?

Missions like these have fundamentally transformed our understanding of gamma-ray bursts. Before these satellites, GRB observations were limited and often inconsistent, making it difficult to identify statistical patterns or understand their true nature.

BATSE, aboard the Compton Gamma Ray Observatory, provided the first large, uniform dataset of GRBs, allowing us to recognize their isotropic distribution and identify hints of a possible third class of bursts. This marked a turning point, moving GRB research from isolated detections to systematic, population-level studies.

The BeppoSAX satellite enabled the discovery of afterglows in X-rays and optical wavelengths, connecting GRBs to host galaxies and confirming their extragalactic origin. Following this, Swift added rapid localization capabilities, allowing astronomers worldwide to observe afterglows within minutes, and providing a wealth of multi-wavelength data.

Fermi expanded our view further by observing GRBs at the highest energies, revealing the complexity of prompt emission and energy spectra. The combination of these missions has allowed us not only to refine GRB classifications but also to study their physical mechanisms, environments, and cosmological implications.

In short, these missions turned GRBs from mysterious, sporadic flashes into a rich, multi-dimensional field of research — one where statistical analysis, theoretical modeling, and coordinated observations work together to unlock the secrets of the most energetic events in the Universe.

9. Your work relies heavily on statistical analysis of large datasets. Could you share how you approach finding meaningful patterns in astronomical data?

Statistical analysis is central to modern astrophysics, especially when studying gamma-ray bursts. These events are rare, highly variable, and often observed under different instruments, therefore careful analysis is crucial to distinguish real cosmic patterns from noise or selection effects.

My approach typically involves several steps. First, I ensure that the dataset is as complete and homogeneous as possible, correcting for known observational biases from each instrument. Then, I apply multivariate statistical techniques, such as clustering algorithms, principal component analysis, and likelihood modeling, to identify structures or correlations that are not immediately obvious.

I also rely heavily on Monte Carlo simulations and synthetic data generation. By comparing observations to randomized datasets that mimic the instrument’s sensitivity and selection effects, we can quantify how likely it is that a pattern is genuine rather than a statistical fluctuation.

Finally, collaboration with colleagues is essential. Interpreting patterns requires both statistical rigor and physical insight, and discussing results with experts in theory, instrumentation, and observation helps ensure that our conclusions are robust.

For the last decade we developed collaboration with the Rényi Mathematical institute, especially with professor Tusnády, who is expert in statistics.

For me, the thrill lies in discovering subtle trends in massive datasets — patterns that can reveal new astrophysical processes or even challenge our understanding of the cosmos itself.

10, Has there ever been a moment when a surprising or contradictory result changed the direction of your research?

Yes. In 1990 the so-called pencil-beam survey was published in the Nature magazine. That was the deepest galaxy survey that time. It goes to 5 billion light-years. It was the second suggestion that galaxy clusters not the biggest structures in the Universe. There were 15-20 galaxies forming 3-4 groups and between them there were practically no galaxy.

Béla Lukács and I discussed that with György Paál and we published 3 papers. In these paper we ask whether the grouping is quasiperiodic in space. We got better periodicity with a non zero cosmological constant. These publications were published years before the supernova surveys.

Our suggested term was 0.67, which is close to the today’s accepted value.

11, What do you think the next decade holds for GRB studies — especially with upcoming observatories like the Vera Rubin Observatory, THESEUS, or SVOM?

The next decade promises to be transformative for GRB research. With observatories like these, we are entering an era of unprecedented coverage, sensitivity, and coordination across wavelengths. THESEUS and SVOM will detect bursts with improved localization and spectral resolution, expanding our ability to study faint or high-redshift events. Meanwhile, Vera Rubin’s wide-field optical surveys will help identify host galaxies and afterglows more rapidly, linking GRBs to their environments and large-scale structures. Combined with multi-messenger observations — from gravitational waves to neutrinos — these missions will allow us to explore GRB progenitors and their role in cosmic evolution in greater detail than ever before.

Research in the coming decade will focus on the following areas:

Multi-messenger astronomy:

The biggest breakthrough will be the simultaneous detection of gamma-ray bursts and gravitational waves. Short GRBs, which are thought to be produced by the merger of neutron stars, also emit gravitational waves. The combined study of these two signals (electromagnetic and gravitational) will open a completely new window on the physics of extremely dense matter and the formation of heavy elements.

The landmark event GW170817, detected by LIGO and Virgo and accompanied by GRB 170817A, provided the first direct confirmation that binary neutron star mergers are indeed the progenitors of short GRBs. This was one of the most remarkable achievements of modern astrophysics — a true “Rosetta Stone” moment that linked light and gravity from the same cataclysmic source. Many scientists hope that future missions will detect many more such events. I am skeptical, since the GW170817 was the closest gravitational wave detected and the GRB 170817A was the second closest gamma-ray busts. So, I think we have a very slim chance to detect another one within years.

Second, Exploring the early Universe:

GRBs are extremely bright, so they can be detected from huge distances. They can be seen as cosmic “lighthouses” whose light penetrates the neutral gas that fills the young Universe. By studying the most distant GRBs, astronomers can gain direct insight into:

The formation of the first stars

and

The birth of the first galaxies,

And the era of reionization, when ultraviolet radiation from the first stars and galaxies ionized the hydrogen filling the cosmos.

Because long GRBs are associated with the collapse of massive stars, observing them at high redshifts gives us a unique glimpse into the deaths of the first stellar generations — effectively connecting gamma-ray burst astronomy with the history of star formation itself. THESEUS, in particular, is designed to identify such high-redshift GRBs and analyze their afterglows to trace the chemical enrichment of the early Universe.

12, What do you believe is the next big challenge or discovery that astronomers will face in the coming decade?

In the next decade, astronomy will face the enormous challenge of managing and interpreting an unprecedented flood of data. The Vera Rubin Observatory alone will generate tens of terabytes of information every night, revealing millions of transient events across the sky. The real difficulty will not be in collecting data, but in understanding it — distinguishing meaningful cosmic signals from noise and instrumental artifacts. Artificial intelligence and machine learning will become essential tools, capable of recognizing subtle patterns, classifying events in real time, and uncovering relationships that would be invisible to traditional analysis. The combination of massive datasets and intelligent algorithms will open a new era of discovery, allowing astronomers to explore the cosmos dynamically, almost as it evolves. In this sense, the biggest challenge — and the greatest opportunity — will be to teach machines how to see the sky with us.

This data revolution will become even more crucial as we enter the era of multi-messenger astronomy, where observations from gamma rays, gravitational waves, neutrinos, and radio signals must be analyzed together. When detectors like LIGO, Virgo, and KAGRA identify a gravitational-wave signal from a neutron star merger, telescopes around the world — including those detecting GRBs — must respond within seconds. Coordinating and interpreting this deluge of heterogeneous data will be beyond human capacity alone. Here, AI will play a transformative role: algorithms trained on both simulated and real events will be able to recognize transient counterparts, predict likely host galaxies, and prioritize follow-up observations.

Moreover, the use of AI-driven data pipelines will change how discoveries are made. Instead of humans searching for rare coincidences between gravitational-wave alerts and gamma-ray bursts, intelligent systems will continuously scan the sky, learning from every new detection. The next great discoveries — new classes of transient phenomena or unknown types of progenitors — may well be first spotted not by an astronomer, but by an algorithm designed to notice what we might otherwise overlook.

Astronomy, therefore, stands on the threshold of a new partnership between human curiosity and artificial intelligence — one that will reshape how we discover and understand the most extreme events in the cosmos.

13, What's the most memorable moment you've had in your scientific career?

I already mentioned, with György Paal and Béla Lukács we found it is likely the cosmological constant is non zero. Very surprising.

The most memorable, when I found out the reaction of the suggestion of the Hercules–Corona Borealis Great Wall. First it appeared in Wikipedia and later there were a huge media response. Scientific videos came out saying the biggest structure is in our Universe is the Hercules–Corona Borealis Great Wall. Journalist ask us several times an interview about it. So we ask Professor Hakkila, the co-founder of the Great Wall to take the interviews. He did a very good jobs.

14, If you could recommend a book to anyone, which one would it be?

There is a BBC program called “Desert Island Discs”, they ask the guests similar question; to choose a book which they would take with them to a desert island. Guests are also automatically given the Complete Works of Shakespeare and the Bible. So I am not starting with the Bible.

However, I have several suggestions:

For non science Tolstoy’s War and peace, which

captures the full spectrum of human experience — from the intimacy of personal struggle to the vast forces shaping history.

Secondly, the Landau minimum; Landau and Lifshitz, Theoretical Physics books.

The Landau and Lifshitz, Theoretical Physics series has been a steady companion throughout my career. These books demand focus and patience, but they give back much more than they take. Each chapter shows how careful reasoning and clear mathematics can make even difficult ideas understandable. I appreciate their precision and simplicity — they never use more words than necessary, yet every sentence carries weight.

Next is my favorite book on gamma-ray bursts, written by my friend Bing Zhang. It is both clear and inspiring, combining solid theory with many examples from real observations. What I like most is that it helps readers see the connections between different ideas in a simple and honest way. Bing has a rare talent for explaining difficult topics without making them feel heavy. Whenever I read his book, I am reminded how much good science depends on clarity, curiosity, and careful work.

And above all: the Cultural History of Physics, written by the father of the billionaire Charles Simonyi, Károly Simonyi. It’s a remarkable book because it connects the development of physics with the broader history of culture and ideas. Simonyi shows how science has always been part of human thought, not separate from it. I admire how deeply the book reflects on both the beauty of physical laws and the people behind them. It reminds me that science is not only about results, but also about the long, shared journey of understanding.

This is an amazing book, full of wonder.

15. Is there anything you've always wanted to do but haven't had the chance yet?

Mathematics amazes me. But nowadays one cannot be a mathematician and an astronomer too, like Gauss.

Therefore I am not doing mathematical research, however I use lots of maths and many times I have to learn new mathematics which is need for our research.

But I still thinking about prime numbers. I calculated lots of consecutive prime differences. Sometimes for a two thousand digit primes. Amazing. Big prime numbers looks like random numbers.

May be in the next decade I’ll have time to work on primes.

16. What advice would you give to young scientists and astronomers who are just starting out in this field?

What I would tell young scientists is to stay curious and never stop asking questions. Curiosity is the real engine of science — not awards, not positions, but the need to understand something that no one has explained before. Learn as much as you can, both within and beyond your field, because discoveries often happen where two ideas meet. Be patient: progress in science takes time, and failures are almost as important as successes. Also, don’t be afraid of big data or artificial intelligence — these are tools that will help you see patterns that older generations could only imagine.

Follow your dreams and try to do what you really like to do.

Lastly, find a good mentor. Does your mentor support you and train you? A head of the department probably would not be the best one.

17. Is there a science fact or cosmic mystery that still amazes you no matter how often you think about it?

Cosmic anisotropy.

What continues to amaze me most is the possibility that the Universe might not be as uniform as we have long assumed. The cosmological principle says that the Universe is homogeneous and isotropic on large scales.

However, when we make a map of the large scale of the Universe, using galaxies and galaxy clusters, we always find almost as large structures as big as our map.

Specially, when we examine the distribution of gamma-ray bursts we practically see the whole observable Universe. And we found a 10 billion light year big structure.

If these features are real, they challenge one of the most fundamental assumptions in cosmology. To me, that is both humbling and thrilling.

18, Is there anything you'd like to discuss that we haven't covered yet?

Yes. Although we had always been on a good relation with the Fermi group, many years ago this got even better. Our former student Peter Veres now lives in Huntsville and works as a part of the Fermi team. So, now we have closer connection with NASA.

Watch the full conversation below.